AN ABSTRACT OF TW TILiS]
OF
Redacted for privacy
An tnvestigation was made of the influence that agonistic
behavior ma.y have in regulating population densities of the
Nontane vole, Microtus montanus montanus (Peale)
conducted on the
The study was
. A. Gaary ranch, Kiamath County, Oregon, from
The objectives were
June, ]$63, to March, 1965.
(i) to determine
if cert.ain measures of agonia tic behavior influence density,
reproduction, sex and
gs composition, and survival of voles from
parent populations of different densities; and (2) to investigate
the role that agonistie behavior and population density play in the
dispersal movement of voles,
Seven one-quarter acre enclosures, containing high numbers
arising £z'c*u different initial parenb stocks, and one field plot,
with a low density population, were live trapped periodically to
determine their characteristics.
fi'e of seven enclosures
Mice were able to disperse from
Observations of agonis tic behavior were
made in controlled behavior trials of mica from these populations.
aperent in the vol& po1atiors
Aonj,s tic bezaior was rnor
Diaperal
that reaehed the higher densiti
veent waa mtgg*sted
te reduce 1ntr-3pocii1c srif by t.eporari1y loweriri
th
ffrst and
This was nt
yei high density pr11ation5.
c
denatties of
.) rvidrt in rAii third year high density popilations.
Adult
iiaie vlea of he 1w dn3ity popalation utiuizod tore threat
behavior than contac
fighting behavior.
Agonts tic behavior was ioz'e pronounced in the high denaity
uoilatios containing a hither nwber of adults.
f tales
A larger ratio
-.o iaies was augostd 'o incr,ase fighting behavior
during high densities
Increased intraspscific strife wa indicated tc have ru1ted
fIh1
uiions exhibiting hiher
roduc4ve p-irforitance fcr
in lower
sverae. ?rena..l
:irr
ortality, IhiCh
be inducd by tntraisoific strife, held dom th
lvL of a
md.3d
lation t11 t) i
o decraa
b
a
..s s.içted to
j'ak density
uvcmil
this study4
as d3nsitL3 increased
survival
kgonistic behavior was
:rs factor which lirtited survival when pop-.
ulat.trris :ore a. itor dcriitte.
xplora cry hhavior corbined with fight.iri
indicat.d to
dispersi-n which increases with
)O)ULIticfl dCTiiO5..
Yjee of 5eC)O
oxrinccd r-re fighting bofor
first yiar
behavior was
pit1ationa
and
andtn
h1rd 7'D po1lat.i3ns
disersd han rice of
Non-dtspersal iales
plyd 're
agonistic behavior than dispersal nL&1e8 of the 1963 populations.
This study indicates that agonistic behavior, which influences dispersal movement, survival, and, to a lesser extent,
reproduction is a factor in the regulation of high density vole
populations.
Redacted for privacy
In Charge of' Major
Redacted for privacy
Redacted for privacy
Dean of Gaa School
Date thesis is resented
Typed by Electra Whetstone
/
/
3
AGONISTIC EHAVIOR IN !4ONANE VOLES,
MIcROUS 1ONTAUS, FR
DIFFE2.E
DENS TRIES
aubinitted to
OREGON STATE UNIVERSiTY
in partial fulfillment of
the requirements for the
degree of
MASTER OF SCIENCE
June l6S
The author wishes to express his appreciation to the following
persons who made this thesis possible:
Sincere thanks are given to Mr. Edward L.Hansen, Instructor,
Department of Fisheries and Wildlife, Oregon State University, for
his assistance, guidance, and supervision throughout the study.
The author is very greatl'ul to Mr. Howard Wight, Associate Professor,
and Mr. Lee Kuhn,
Associate Professor, Department of Fisheries and
Wildlife, Oregon State University, for their helpful criticism in
the preparation of this thesis.
Thanks are extended to Mr. Jerome
Smith, graduate research assistant, for his
and laboratory work.
assistance in field
The office and laboratory facilities provided
by Mr. Gene Gross, supervisor of the Kiamath Branch Experiment
Station, are appreciated.
Mr. Edward Geary provided the land upon
which the enclosures were built and thus mede this study possible.
A final thank you is due my wife, Charlotte, for her help in tyLng
the rough draft of this thesis.
TABLE OF COTE5
Page
INTRO1JcTION.. ...
.......
.. .. ................ .......
3.
. . . . . . a * a a a a * a a
6
. . ..
6
. . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7
Contact Behavior.... .n...........e.......t..a...e.,.....,ea
7
Agosic Behavior. . . . . . . . . . . . . .
8
Disposition.
. * . . * . * . . . . . . . . . . . . . * a a *
Maintenance. . . . . . . . . . . .
. . . .
. *
Expiox'atory l3ehavior. . . . * .
Attao and Retaliation. . . . . . .
Threat. .
*
.
.
. . . . * . . .. . .
. . . . . . .
. . . . * . . . . .
. .
.
. . .
. . .
.
9
. * . . . . . . * . . . . . . . . . . * . . . * . . . . . . . . . . . . . . * . . . . . . . . . . . .
12
Retreat and Avoidance...,.. ...
. . , .
. . . . . . . .
. * .
. . . . . . . . .
... ....... ......... ......
12
Submissive Behavior........................................
12
..
. . . . . . . . . . . . . * * . . . . . . .
lb
Territoriality..............-.................................
15
Displacement Activity. . . . * .
. . . . . . * . . .
15
16
Study Area.... ..... ............,.,...........,.......,......
16
Eno1oeureaandTheirPopu1ations............................
16
Caledonia-6 Field Plot...................................,...
19
Dispersal Ramps..............................................
19
Live Trapping. *a#*****t***Ø*s**ø**..****a**eS****a*Ø
20
acteristica... .... .........
22
Determination of Population C]Behavior Studies. . . . .
. . . . . .
. . . . * .
. . . . . . . . . . . . . . . * . . . . . . . . .
23
TABLE OF COEWS - CONTINUED
RESULTS
B
a . . a . .
. . . .
Behavior Characteristics.
B
*
a
B
a a a a a a .
.
a . a
a
a
.
. . * .
a a a a a a a a a a a
2
28
Agonistic Behavior Patterns of the
28
Non-dispersal Nice Coared to Dispersal NiC6...a.a.asaa.*
314
Solitary Behavior Patterns a
a.
a a
38
B B S B a
a B
140
Trapping Periods..,....BB.....B...B..B......B......,.....
140
Population 1)SflSiti$B.Ba.*..B.....B.a...*a..WB*.B...a.aa...B
142
Sex and Ago COmpOsitiofl.... a. a. a.. .. *..,a.. ..a a.., a. *
51
Reproduction.B..aa....a..a...e..B..B...B.s...*.a.B....*-..a.
55
General Survjval....................B...B.,................
62
Dispersal Rflfl1$a.....a...a*a..I..aa..aaB..B..aaea..a**aB*.s
71
Wounding. B S B a
77
Population Characteristics B
* a a B B S a a S * B B *
DISCUSSION..... ala .aa..a. a.
a a a s a a a a * a
a a a a a a a a ,
. B a a B
B a a B
B
B
* S B B S a B B S B * a S B B
B * B B Ô
S * B
S *
a
S a a B B
S B B S B
83
aas I,. B* *0** 5*5*0 SB .BaB*,BB.
5
83
...
86
AgonisticBehaviorVersusRsproduction.......................
87
AgonisticBehaviorVersusGeneralSurvival...................
89
Agonistic Behavior Versus Dispersa1Movement.................
90
ONGI.tJSIONS. a S. BaBB. Ba..... *ta*s * a BS** a.a..,S. a... Ba BBBa B * Baa
93
Agonistic Behavior Versus Population Dens3.ties.,
Agonistic Behavior Versus Sex and Age Composition.
a *a**a* SB
**
BISLIOGRAPHY.... as...,.. a.. ...a.aea SaBB*e a. aaa*ØS.S.sBaa.
95
LIST OF FIGURES
Page
Figure
vole approaching a subordinate vole............
1.
Dominant
2.
Retaliation of a subordinate vole (left) from a
dominant vole (right). . ..... ... ... ...s .. i .. ....
3.
b.
Two voles pushing and boxing
....
11
. . . .. . . . . . .. . . . . . . ..
13
each other with their
forepaws. .. . .. . . .. . . . . . . . .. . . .
* . .
iunway of a dispersal ran leaving an enclosure. Note
the wood box at the end of the ra containing a treadle
which drops a mouse into the capture bucket.............
5.
6.
10
21
Top view of a capture bucket, containing a mouse, which
has been removed from beneath the treadle box...........
21
The dual couartment cage was divided by a partition
containing a hole and a sliding door through which
either mouse was able to cross to the opponents aide
ciuring a trial..........................................
2
7.
Headwouudsofanadultvole............................
79
8.
Rump wounds of an adult vole..........................,.
80
LIST OF TABLES
Table
Page
I.
II.
STOCKfl
HISTORY AND POPULATION PHASE SEQUENCE
FORENCLOSURES iTO 7....,.........................
18
NUMBER TRIAL NICE AND DUAL BEAVIOR TRIAlS AND
AVERAGES OF FIGHPING TDE, AGGRESSIVE AND
DEFENSIVE FIGIff 1MG, AND DOMINANCE AND
SUBORDINANCE FOR THE POPULATIONS REPRESEING
III.
IV.
THE FIRST, SECOND, AND THIRD HIGH DENSITY YEAR
PHASESFOR 1963 AND 196b. . . . * . . . . . . .
.. . . . . . . .
29
AVERAGE JYJAL TRIAL BEHAVIOR CHARACERISTIC5 OF
A]JLT MALE MICE FROM ENCLOSURES 1 TO 7 FROM
JUNE THROUGH OCL'OBER, 1963. . . . . . . . . . . . * . . . . . .
31
AVERAGE BEHAV10T? CHARACrEBISTICS OF AIULT MALE
MICE FROM ENCLOSURES 1 TO 7 AND THE QALEDONIA-6
PLCIP FROM JUNE TO DECEMBER, 196b..................
V.
AVERAGE AGONIST IC BEHAVIOR CHARACTERISTICS FOR
ArVLT MALE NON-DISPERSAL AND DISPERSAL MICE
FROM ENCLOSURES 1, 2, 5, 3, AND 6 FROM JUNE
THR.cJGH OCTOBER, 1963. ........ . . . . . . . . . . . . . . . . . . .
VI.
35
AVERAGE AGONISTIC BEHAVIOR CHARACTERISTICS FOR
AIIJLT MALE NON-DISPERSAL AND DISPERSAL MICE
FROM ENCLOSURES 1, 2, 5, 3, AND 6 FROM JUNE
THROUGH DECIBER, 196b. . . . . . . . . . . . . * . . . . . . . . . .
VII.
32
37
EXPLORATORY, ACTIVE, INACTIVE, AND WASHING AND
GROOMING SOLITARY BEHAVIOR CHARACTERISTICS FOR
DISPERSAL MICE CAFflTItED IN RAMPS 1, 2, 5, 3,
AND 6 AND FOR NON-DISPERSAL MICE FROM TEZE
ENCLOSURES ILIRING JUNE THROUGH OCTOBER, 1963.......
VIII.
EXPLORATORY, ACTIVE, INACTIVE, AND WASHING AND
GROOMING SOLITARY BEHAVIOR CHARACTERISTICS OF
DISPERSAL NICE FROM RAMPS 1, 2, 5, 3, AND 6
THROUGHJUNETODECEMBER,19& .............
IX.
39
.......,
hi.
TRAP PERIOD DESIGNATIONS FOR 1 14, I 2d, AND
II 3d FROM JUNE, 1963,
THROUGH JANUARY, 196b.......
li.3
LIST OF TABLES
CONTINUEI)
Page
Table
X
TRAP PERIOD DESIGNATION FOR II 34, II 2d,
II Sa, AND LI 7 FRC*I MAY THROUGH DECEMBER,
1964. . * .
XI.
. . . a a
a
a a *
*
a. a a a a a a a a
TRAP PERIOD DESIGNATION FOR III 3d.
a
* a a a a a a a a a a a a
414
III 14
In 6d, AND THE CALED0Nm.-6 r'iør Fac x
THROUGHDECI}i3]t, 19614. a a
XII.
a a a a
a a a a . a a a a a a a a a a a a a a a a
145
TOTAL 141CR CAPIVRED, POPULATION EST4ATE,
DENSiTY PER AE, AND THE NUMBER DEAD IN
XIII.
XIV.
XV.
XVI
TRAPS FOR ENCLOSURES 1, 2, 5, 7, 3, 14, AND
6 FROM JUNE, 1963, TO JANUARY, 19614...........,....
46
TOTAL MICE CAF'rURED, POPULATION ESTmATE,
DENSITY PEL. ACRE, AND THE NUMBER DEAD IN
TRAPS FOR ENCLOSURES 1 THROUGH 7 AND FOR
CALEDONIA-6 PLOT FROM MAY THROUGH
DECEMBER, 1964.....................,....,..........
48
PERCENTAGE OF AWLTS, NUMBER OF MALES AND
FEMALES, THEIR KEANS, AND THE SEX RATIOS
JUNE, 1963,
FOR I 14, I 2d, AND II 3d, FR(
TOJANUARY, 196Li..............,.....,..........,.,..
52
PERCENTAGES OF AIXJLTS, NUMBER OF MALES AND
FEMALES, THEIR MEANS, AND THE SEX RATIOS
FOR ENCLOSURES 1 TO 7 AND FOR CALEDONIA.-6
PLOT FROM MAY TO DECEMBER, 1964....................
53
NUMBER OF SUB-A1TLT AND AJJLT FEMALES AND
PERCEAOES OF THESE FEMALES PERFORATE,
PREX3NANT, OR WITH MAMMARY GLANDS LARGE OR
LACTATING, AND THEIR MEANS FOR ENCLOSURES
1 THROUGH 7 FROM JULY TO NOWi}1BER OR
DECEMBER, 1963..................,........,.........
XVII.
56
NUMBER OF SUB-A1JLT AND AThJLT FEMALES AND
PERCENTAGES OF THESE FEMALES PERFORATE,
PREGNANr, OR WITH MAMMARY GLANDS LARGE OR
LACTATING AND THEIR MEANS FOR ENCLOSURES
3. THROUGH. 7 AND THE C.kLEDONIA-6 PLOT FROM
MAYTO J3ECEMBER, 1964........... ...a.a*.a.aa..,..
59
Table
XVIII.
SURVIVAL RATES FOR AIXILTS, SUB-A1JLTS,
AND JUVENILES C(1'1BINED FOR I Id, I 2d,
AND II 3d FR
1963.. ...,.,
Xii.
JUNE THR.OUGH DEC]NB,
. os. ......a...s.a...4o .....**
63
SURVIVAL RATES OF ALiJLTS, SUB-.AIJJLTS,
AND JUVENILES IN II ld FRC MAY TO
DEC11B]Ft, 19614.....................................
XX.
SURVIVAL RATES OF ALULTS, SUB-LWLTS,
AND UVENDJES IN II 2d FRC MAY TO
........ .. .
DECF'IBER,l9614.. ... . . . .... .. ....
XXI.
. . . . . , . . . * . . . . . . .
68
SURVIVAL RATES OF A]IJLTS, SUB-AII]LTS,
AND JUVENILES IN III 6d FROM NAY TO
DECEMBER., 196!i.........,...................,.......
XXV.
67
SURVIVAL OF AWLTS, SUB-AWLTS, AND
JUVENILES IN II Sd FROM NAY TO
DECEMBER, 19614............,........................
XXIV.
66
SURVIVAL RATES OF AILtLTS, SiJB-AIULTS, AND
JUVENILES IN III b FROM MAY TO DECENBER,
196b. . . . * . . . . . . . * . . . . . . . * . . . . . . .
XXIII.
65
SURVIVAL RATES OF AWLTS, SUB-AWLTS, AND
JUVENILES IN III 3d FR( MAY TO DECMBaR,
196b. .. .. .. . .. . .... .... ..... ......... .... ... ....
XXII.
6b
69
SURVIVAL RATES OF AIJLTS, STJB-AWLTS, AND
JUVENILES IN II 7 FROM MAY TO DECE}IBER.,
XXVI.
.. ... ...,..... ........ ..... . ..... . ........
70
TOTAL NICE GAUGI, CAP2URES PER RAMP DAY,
POPULATIOI ESTATE, AN]) }RCENT SCARS AN])
WWNDS OF NICE AFflJRED IN TI DISPERSAL
RAMPS FROM JULY 2, 1963, TO NOVEMBER 15,
1963.. ...... ...... ..... ... ..... ,.......... ....
72
LIST OF TABLES - CONTINUED
Table
XXVII.
Page
T(YLAL NICE CAUGI, CAPTURES PER RAMP
DA.Y, POPULATION ESTfl4ATE, AND PEECXL'
SCARS AND WOUNDS OF MICE CAPTURED IN
TH DISPERSAL RAMPS FROM JUNE 2)4, 196)4,
TO DECE'iBER. 9, 19613. ...........
XXVIII.
7!i
MONTHLY PERCENTAGES AND MEAN ANNUAL
PERCENTAGES OF WOUNDS AND SCARS FOUND ON
MICE CAPTURED, AND TtLi TOTAL CAPTURE FOR
EN(1OSUES 1 THROUGH 7 FROM JUNE, 1963, TO
JANUAt.Y, 196)4... .......................... ..,.....,.
XXIX.
81
MONTHLY PERCENTAGES AND MEAN ANNUAL
PERCENTAGES OF WCIINDS AND SCARS FOUND
ON MICE CAPTURED, AND TILE TOTAL
CAPJ1URE FOR ENCLOSURES 1 THROUGH 7 AND
CALEDONIA-6 PLOT FROM MAY TO DECE2!IBER,
196)4 .................... , , * * . . ..........
XXX.
. . . . . . . . . .
82
AVERAGE FIGIfl]3 TflIES AND PEAK DENSITY
ESTATES- FOR MICE OF ENCLOSURES 1 THROUGH
7 tJRING 1963 AND 196)4 ................ .....,.........
8)4
AGRONISTIC BkVIOR IN MONL4JE VOLES,
HIGROTUS NONTLNUS, FRC* DIFFERENT
PARENT POPULA!ION DFSITI5
This report presents the results of a field and laboratory investigation of agonietic behavioral patterns observed in populations of
the I1ontane vole, Microtus montarius montanus (Peale), derived from
parent populations of different densities *
The purpose of this study
was to determine the possible influence of agonistic behavior in the
regulation of meadow mouse densities
The field work for this study
was conducted on the E. A. Geary Rench, flamath County, Oregon, from
June, 1963, to March, 1965.
Th objetiee were:
(1) to determine if certain measures of,
agonistjc behavior influence density, reproduction, sex and age
composition, ar$ survival of voles from parent populations of different
densities; and (2) to investigate the role that agonistic behavior and
population density play in the dispersal movement of voles.
In April, 1958, a research project, entitled The life history
of the meadow mouse, Microtus montanus, in Oregon, with particular
reference to factors influencing seasonal
and annual population
trends," was started by the Oregon Agriculture Experiment Station
under the direction of the Department of Fisheries and Wildlife.
Since October, 1960, the program has received additional support from
the United States Public Health Service (Research Grant 7758).
report is the fourth graduate study resulting from this project.
This
L
The history of Miorotine fluctuations and irruptions has been
recorded in Europe and Asia for centuries (Elton, l9I2).
Such
plagues and economic losses have exotted the interests of biologists
to the point that an extensive amount of literature has accumulated
on this subject (Elton, 11.2).
Periodic fluctuations of small mammal populations have not been
satisfactorily explained.
Research work in the l93Os and l91O's
emphasized mortality factors such as prodation,parasitism and disease,
climatic conditions, and reduced food supplies (Hamilton, 1937).
Chitty1 s (1952; 1955) studies of the vole, Nicrotus agreatis, revealed
that fluctuations occurred every three or four years and tended to be
synchronized.
None of the above mortality factors appeared to be
important because they were not synchronized with the cycle (Chitty,
1955).
Chitty (1952) suggested that intraspecific strife is of
primary importance in determining the size of natural populations of
the vole.
He inferred that high juvenile mortality was a symptom of
severe intraspecific strife, and that this strife probably affected
the hormone balance of females so that their young suffered defects
which reduced their survival rate and impaired their ability to
produce a normal generation.
He hypothesized that the condition of
one generation affects the breeding of the next two (Cliitty, 1952).
Clarke (1955), working with }ttcrotua agrestis, used outdoor
cages to study the influence of density on the reproduction and
survival of two experimental vole populations.
Fighting and chasing
were observed in both populations, but aggressive activity and wounding
3
were more frequent in the cage with the highest population.
limited
cluded that the strife
He con-
population growth in both populations
but was mOre apparent in the higher density population.
Louch (19S6) used indoor pens in studying populations of Microtus
psylvaniotzs penneylvanicus (Ord) to test the hypothesis that high
population density is a stress factor which may limit population growth.
He found that reproduction did not change with an increased population
density, but that litter and
adult
surviv-al decreased &t high density
levels. The increased litter iortality was apparently due to a disturbance of the lactating females from over crowded population conditions.
The high adult mortality rates were attributed to
an increased incidence
of infectious disease at higher densities.
Frank (l9?), studying the behavior of Microtus arvalis (Pallas)
in outdoor pens, concluded that social behavior was important in regulating population growth.
He emphasized that population increases result
from the reproductive potential, the carrying capacity, and the condensation potential.
The condensation potential mechanism can be said
to be in effect when the home range is reduced, when social comnunities
of females and families develop, and excess males are eliminated. The
mechanism permits a cyclic species to live at an uncommonly high density.
Frank further states, a rapid population increase cannot be regulated
by normal mortality and dispersal, and when a supportable density is
exceeded, a population crash occurs.
"$hock-disease," a condition
associated with physiological derangements involving low blood-sugar
and glycogen levels, was Frank's explanation for a population crash.
Chitty (19S5) suisnarized that it populations are not equally
resistant to mortality forces at various levels of abundance then
"the abundance of certain species may be limited primarily through a
change in susceptibility,
and the direct causes of death may vary
according to local circumstances." He further stated that "the
peculiarities of a cycle in numbers cannot be attributed to depletion
of the food supply."
Chitty (l97) found that descendants of voles
which had been cravded had enlarged spleens even after a generation
of low density, and this pathological condition which terminates a
period of abundance probably Is controlled by a hereditary factor.
Chitty (1960) proposed the general hypothesis that "all species
are capable of regulating their own population densities without
destroying the renewable resources of their enviroument or requiring
enemies or bad weather to keep them train doing so." The effects of
independent events, such as weather, became more severe as numbers
rise and the quality of' the population falls.
The offspring of a population are lost except those that replace
the older animals.
Besides the mortality factors conmon to a par-
ticular population there is a mechanism that eliminates the remaining
surplus. Chitty's polymorphic-behavior hypothesIs is the most recent
attempt to explain this mechanism (Krebs, 1963). Chitty has proposed
(Krebe, 1963) that populations change in quality during changes in
abundance.
He suggested that the mechanism was mutual antagonism
associated with high breeding densIties which brings about a change in
the properties of' the population through selection.
Chitty and Phippa
have shown that voles born during a phase of rapid population
(1961)
increase have higher average
adult body weights than those born in
years of limited population growth. They are examining the hypothesis
that a decline in numbers is a necessary consequence of the selective
action of hostility against the genotypes present during the phase of
rapid increase. The evidence that tests Ghitty'a genetic
chanism
is limited.
Aggression seems to be dependent upon genetics (ivia, 1962).
Aggressive behavior patterns within individuals vary, and this
"variation is likely to be influenced genetically, but it is also
related to individual experience" (Barnett, 1957). Smith (196b)
suggests that voles, Microtus montanus montanus (Peale), from a higher
density parent population are selected for aggressiveness, and this
aggressiveness probably causes a disrupted social structure.
Intra-
specific strife causes disrupted social structures characterized by
prenatal mortality, poor nesting care, poor juvenile survival, and
cannabilism (Calhoun, 1962
Clarke,
1955).
Dispersal movement by voles is important in providing a stable
social structure, but as the density of a population increases, the
influence of dispersion on the social structure decreases (Smith,
196)4).
Smith (l96Li) found that where an enclosed high density parent
population was not allowed to disperse, the prenatal mortality and the
amount o± wounding, caused by aggression, was greater than if dispersion was allowed or where voles were from a low density parent pop-
ulation.
A study of behavioral changes occurring in vole pojilationa may
reveal a clearer explanation of the regulation of population densities.
The study of animal behavior is of the activity for the whole organism
or groups of organisms. Animal behavior can be divided into solitary
behavior (which includes the activities of a
single animal), arid
social behavior (which includes all behavior patterns involving two
or more interacting animals). The aspects of behavior that are
important to this study are reviewed.
Disposition
Voles seem to possess individuality in dispositions and habits.
Some voles are timid and nervous, while others are gentle (Bailey,
i92l). Voles living in an uncomfortable envirorent are quarrelsome
and often fight to the death. DiZerences in behavior are noted
early when the young are beginning to run about, and Bailey (l921)
implies that these differences seem to be inherited characteristics.
The young are mild mannered until the second or third day after they
open their eyes when they begin to take on the aggressive nature of
the adults (Bailey, l92l).
(aintenance
Washing and grooming activities are common in conflict situations.
Washing begins with rairld motions of the paws moving together under the
mouth.
Then the paws are raised to the cheeks and drawn down to the
tip of the nose. Foflowing this procedure are longer strokes of the
L
7
paws that reach to the ears and are accompanied with a bobbing motion
of the head.
Next th
flanks and back are combed with the forepaws
while mouthing the fur with a bobbing head motion.
Scratching with
the hind feet occurs often during the cleaning procedure of the entire
body (Clarke, 1955).
ploratory Behavior
The exploratory behavior of a vole serves to acquaint it with
the habitat in which it lives.
When a mouse is placed into a strange
area, it begins to explore its surroundings.
Initially the body is
tense and extended, and this Is termed the "elongate posture"
(Eisenberg, 1962).
The mouse moves in short runs, but soon discards
Noseing
the elongate posture and moves by means of a slower walk.
is a very important part of a voles investigation, and during these
movements a mouse often rears up on his hind legs, nods its head, and
tests the air with its nose.
When a new object is encountered, the
exploratory actIvity pattern is prolonged (Shillito, 1963).
Exploratory
behavior combined With fighting and conflict tends to promote dispersion
and movement in Norway rate (Barnett, 1957).
Contact Behavior
When two mice encounter one another, the contact may be made in
a nose to nose or nasa-anal fashion (Eissnberg, 1962).
Often among
adult males, fighting is initiated immediately upon contact, and
naso-nasal. contact is not experienced.
The distinction between sexes
by mice seems to be made rapidi(Eiaenberg, 1962),
Agonistic Behavior
Agonistic behavior, as defined by Scott (1962), is the involv-.
merit of fighting, escapement, defensive posture, and passive behavior
patterns
Any sort of adaptation which is connected with a contest or
conflict between two animals may be included in this term.
A summary (Clark, 1962) of literature concerning Lighting and
hostility in animals emphasizes the following characteristic principles
of agonistic behavior.
1.
Fighting is affected by learning.
Success in fighting
re-inforces aggressive behavior.
2.
Social structure of populations limits the destructive
levels of aggression.
Dominance may be formed by older animals over
younger ones without serious fighting.
established the relationships
peaceful manner.
After a dominance
order is
of animals can be stabilized in a
Threats by dominance are reacted to in a submissive
way by lower hierarchy animals.
3.
The territoriality phenomenon is important in reducing
lethal combat, but, on the other hand, a violation of territory rights
can cause fighting.
b
Animals disorganized in their social or geographic factors
may experience an increased incidence of destructive, agonistic
behavior.
Scott (1962) states that deer mice fight only when two
conditions are present.
First, when there is a disorganized pop-
ulation and strangers are forcibly brought together, and second,
when the mice cannot possibly escape.
5.
Fighting behavior is brought about by an animal's response
to edernal stimulation.
Males more frequently than females inflict wounds on other voles,
usually other adult males (Bailey, 192b; Frank, 1957).
Males will not
tolerate each other when they are in the presence of females (Carter,
1963).
Some males are more successful in Lights than others, and they
come to be the dc*rth2auts of the population.
A female in advanced
pregnancy or with a litter will attack any vole that comes near her
nest.
A dominant, male or female, does not necessarily retain its
position within the group (Clarke, 1955).
Attack and Retaliation
The dominant vole may make quick, agitated, jerky rune with
brief pauses before attacking a subordinate (Figure 1).
When moving
in this manner, the body of the dominant is held high off the substrate
and has a sleek appearance.
Before the attack, the dominant will erect
his hair and hunch up his back which makes him look larger.
The
dominant chases and attacks the subordinate, and fighting is the result.
A subordinate may retaliate against the dominant before he is
caught by turning and Lacing his pursuer. A retaliating subordinate
may make a lunge with incisors bared at the dominant vole, or he may
squat on his hind quarters and squeal loudly at the approach of the
aggressor (Figure 2). A subordinate's retaliation often causes a
dominant to retire. After a dominant retreats, he may reapproach the
8ubordinate, and the retaliation process Will
be repeated. Often
10
Figure 1.
Dominant vole approaching a subordinate vole.
ii
Figure 2.
Retaliation of a subordinate vole (left) from a
dominant vole (right).
12
this return of the dominant is vigorous enough to cause the sub ordinate
to run (Clarke, 1955).
In encounters of equally dominant voles, both mice usually stand
or squat on their haunches.
They push and box at each other with
their forepaws as shown in Figure 3, and they may commence to wrestle.
boxing and. wrestling occurs in both young and adult voles (Clarke, 19%).
Threat
The threat pattern is evident when a mouse remains on all fours
with his hair erected, his body hunched up, and, sometimes, his
incisors exposed.
The head may dart at the opposite mouse, and this
threat pattern terminates in a Light, chaèe, or when one mouse moves
away (Clarke, 19%).
Retreat and Avoidance
When a mouse ía defeated he usually flees from the winners 'vicinity.
If chased by the dominant, the subordinate may avoid contact by
leaping away (Eiaenberg, 1962).
Submissive Behavior
A subordinate vole will tolerate the aggressive approach of a
dominant.
behavior".
Clarke (19%) refers to submissive behavior as "appeasing
in usin'
bmiasive behavior an animal doesn't
the aggressor the stimuli which releases an attack.
vovide
This behavior is
shown when a subordinate turns over on his back in front of the
dominant, and a would be attacker ceases
Another posture position
13
4
Figure 3.
Two voles pushing and bod.ng each other with their
forepaws.
I'
that prevents art attack is a "freeze"
sttion by the subordinate in
such a manner that the pale skin of the ock and bee of the ears is
visible.
oceur
Again, no attack
The tail ts usually snarply erected.
even though the dominant tend
near the subordinate (Clarke,
1955).
L'jp].acement .ctivity
Voles exhicit soue behavior activities which seex to be
inappropz'ite,
activity.
ndlar& (195) suggests that they are dieplaceaient
cisplaeement activity (Tinbergen, 1959) is the behavior
expressed when the activated drive of
n aniial is denieci discharge
through the noral conswnmatory acts.
Two drives, such as the flight
drive and the aggressive drive, may conflict with each other and
activate a pattern of behavior that is in?proriate to the ituation
Ixnmeuiately after
uciinant retir .s from
retaliating subordinate
he niay eomnence in a rapid digir.g ..ctiyity.
This inappropriate
activity is aued w'iefl a highly activated agressive drive is
thwartec by an activation of the flight drive (C1rke, 1955).
a
ubordiriata rtay exhibit
which ia again inappropriate.
acitivatiort of the
A±ter
r'id waehng and gr oing ctivity
This activity is caused by
s.ight
ggreasive drive 'when the fligtt orive is activte
(Clarke, 195).
A?he jerky rAoveent
exhibited by attacking males indicate3
cnf4ct between the aggressive
fljg
drjves.
i'hen
zjnate
vole enters a aubordinate's cage, he may express the 2yements of
ttridgeting, marking tilde, waltzing, and dancthg
(aarke, l95),
This behavior seems to indicate an activation of the flight drive as
the aggressive vole enters the opponents cage.
Territoriality
Barnett (19S7) states that flight usually depends on two
conditions:
"being in a familiar place, and encountering a agrariger."
The location of an
encounter will
influence the dominance Or sub-
ordinance of the individuals concerned. Experiemnts have shown that
the familiarization of a compartment and the inpregnation of scent
in the nest is a definite influence on the establishment of territory
behavior (Eisenberg, 1962).
The wounds on the hind q
ters of subordinates are the result
of being chased, and wounds may be present in other areas of the
body it subordinates have been caught.
Dominant voles have wounds on
their headi and necks which are the results of contact with retaliating subordinates or other dominants.
Therefore, some scars on the
head designate dominants, and scars on the hind quarters signify sub-
ordinance (Clarke, 19%).
It is apparent from this review of literature that the mechanisms
for the regulation of Z'!icrotine populations are not completely understood.
This study was established to provide an indication of the role
that agonietic behavior may play in the regulation of vole densities.
Study Area
A one-fifth acre field plot and seven one-quarter acre enclosure
plots are located in the Caledonia-6 pasture on the E. A. (}eary Ranch,
eight miles northwest of IClamath Falls, Oregon. The Caledonia area
has been reclaimed from Upper Klamath Lake and is composed of mucktype soil, rich in organic material, from one to several feet in
depth and overlying a clay substrate.
The water table during the wet
months normally rises to within a few inches of ground level, and
recedes during the dry months to eighteen inches or more below the
surface.
The vegetation
within the study area consists mainly of
meadow foxtil Alopecurus pratensis (L.), bent grass
'oati
pains tris (Hudson), and blue grass Poa pratensia (L.).
The climatic conditions are characterized by warm suxxmers and
cool winters.
Annual precipitation averages about lh inches, half in
the form of snow.
During the dry season, June, July, and August, the
mean monthly temperature is approxtmately 68° F.
The coldest month,
January, averages 30° F (U. S. Weather Bureau, 1963).
Enclosure
and Thei
Populations
The seven one-quarter acre, Umouse proof" enclosures used in
this project were constructed in the spring of
of an enclosure (1Oli feet
1961.
The construction
by 1OL feet) has been explained in detail
by Carter (1963) and Smith (19614).
17
Throughout the study, the enclosures contained mice that
population phases. Phases
originated from different high density
refers to the number of years that the populations have had high
densities.
Four enclosures (1, 2, 5, and 7) were stocked in May,
1963, mith voles from a low, 1962, parent population density (75
mice per acre) that existed in the Caledonia-3 pasture.
three enclosures (3, Lj, and 6)
In May, 1963,
contained voles from a high, 1962,
parent population density (.76 - 792 mice per acre) that originated
The sequence of the stocking
from initial stocking in May, 1962.
and population phases for the seven enclosures is shown in Table I.
By fall o± 1961i., Enclosures 1, 2, 5, and 7 contained populations in
nclosures 3, b, and 6 had
their second year of high density, and
populations in
and 7
their third year of high density. Enclosures 1, 2,
are to be designated as I 1, I 2, 1
when referring to 1963
5, and I 7, respectively,
first year high density enclosures and are to
be designated as II 1, II 2, II
referring
5,
5, and II 7, respectively, when
to 196L second year high densities.
6 are to be designated as II 3, II
b,
and
Enclosures 3, b,
and II 6, respectively, when
referring to 1963 second year high density enclosures and are to be
designated as III 3, III L, III 6, respectively, when referring to
196b third year high densities.
From the arrangement of population phases the behavior and
population characteristics of each generation phase could be compared
to one another to
provide an insight as to
whether or not parent
population density has an influence on ensuing
generations with
TABLE I.
STOCKING HISTORY AND POPULLTION PHASE SEQUENG FOR
ENCLOSURES 1 TO 7.
flA.TE
ENCLOSURES
3, b, and 6
Sjring 1962
Stock-mice from
Caledonia Low
1961 parent
population
Fall 1962
Phase I
First year high
density populations
ENCLOSURES
1, 2, 5, axd 7
Stock-mice from
Caledonia I4ow
1962 parent
population
Project Beginning
Fall 1963
Phase II
Second year high
density populations
Phase I
First year high
density populations
Fall 196h
Phase III
Third year high
density populations
Phase II
Second year high
density populations
respect to agoriietic behavior.
The enclosures were irrigated during the dry months of 1963 and
In the
196b to provide the moat favorable vegetative cover possible.
fall of both years, feed oat8 (10 pounds per enclosure per week) and
bay were placed mithin the enclosures.
Food and neettng material
seemed to be adequate, even though natural foods and cover bad been
depleted when high population densities occurred.
Caledonia-6 Field Plot
In July, l96i, a field grid was set up on the Caledonia-6
pasture adjacent to the seven enclosures.
The objective was to gain
additional information on behavior characteristics of voles living in
low populated areas.
The plot (60 feet by lLiQ feet) consisted of
three rows of seven trap stations.
from July to November.
This plot was trapped once a month
The vegetation was predominantly bent grass,
blue grass, and meadow foxtail, but because o± constant cattle usage,
the grass cover was usually one to two inches high.
Prior to June, 1963, a dispersal ramp was attached to Enclosures
1, 2, 3,
,
and 6.
The letter 1*dff added to the enclosure population
designation indicates a dispersal ramp for the enclosure (I Id, I 2d,
II 3d, I 5d, and II 64).
Smith (l961) baa described the construction
and dimensions of these dispersal ramps.
Each dispersal ramp contained
an open, flat runway which presented no over head cover and was
considered to be an adverse condition to mice moving out of the
20
enclosures (:Figure b).
It seems probable that mice exhibiting
dispersal characteristics would comprise the bulk of voles caught in
the capture bucket at the far end of each ramp (Figure
).
Steel
metal doors between the enclosures and ramps were opened for an
average of 1? days a month for July, August, September, and October,
and opened for three days in November, 1963.
In 196b they were opened
during the period June 23 to December 9 for an average of six days a
month.
The ramps were never opened during adverse weather which may
disrupt the pattern of dispersal movement. Mcs raught in the ramps
were placed in captivity after pertinent data was recorded.
Live Trapping
Live traps wore utilized to catch mice for observation of
behavior and to study the characteristics of the populations.
Grids
were set up and trapped intensively in the above seven enclosures
and Caledonia-6 plot.
The grids were trapped during periods of from
three to five days using Longworth and Sherman live traps.
The number
of traps used in an enclosure for any one trap period ranged from
to 106 depending upon the population density.
3
Traps were baited with
feed oats, set in the evening, and checked the following morning.
Location of capture, sex, age, reproductive status, weight, notes on
wounding, and signs of disease or ectoparasites were recorded for each
mouse captured.
Mice were marked with numbered monel metal tags and
toe clipped (Carter, 1963).
21
Figure b.
Runway of a dispersal ramp leaving an enclosure.
Note the wood box at the end of the ramp containing
a treadle which drops a mouse into the capture
bucket.
V
Figure 5.
Top view of a capture bucket, containing a mouse,
which has been removed from beneath the treadle box.
22
Determination of Population Characteristics
The data gained £rc
live trapping was the basis for calculations
of population densities, reproductive status, sex and age ratios, ew''vival rates, and the amount of wouxiding.
The population statistics
were later correlated with behavior statistics.
The population density for each population trap period was
calculated by the mark and recapture method using the Ltncoln index.
The last day for each trap period was considered the: recapture day.
Confidence limits were established at the five percent significance
level (Davis, 1962).
Reproduction for the population8 was based on the percentage of
sub-adult and adult females having:
(1) a perforate vaginal orifice
(a sign of breeding condition), (2) mammary glands large or lactating,
and (3) palpable pregnancies.
Smith (19614) describes in more detail
the criteria for estimating reproductive status.
Sex was determined by noting the distance between the anus and
penis or clitoris.
This distance is greater in males than females.
Voles were classed as juveniles, sub-adults, or adults.
Their age
classes were determined by size (weight)and pelage (1eke and Kinney,
l9S6; Hothnann, l98).
Minimum survival rates were calculated frcmi enclosure recapture
data kept on each vole.
These rates show the percentage of voles
recaptured for each oóboz't (mice captured for the first time during
any particular trap period).
Survival rates were calculated only
for voles live trapped and excludes voles caught in dispersal zampe
23
or found dead in traps.
To obtain a general indication of survival
among enclosure populations for 196b, the total percent of surviving
voles captured in each month from August through November or December
was averaged, and a mean of these monthly averages was calculated for
each of the seven enclosures.
Tne percentages of voles with scars or wounds were obtained
from the trapping data.
Since all voles are susceptable to wounding,
even though adult males exhibit a greater proportion of the wounds,
the percentages of wounds and scars for each population were based
on the total mice captured and are presented as an indication of the
amount of conflict among voles in each population.
Behavior Studies
A means to obtain a quantitative measurement of the social
interactions was devised and used.
The objective was to determine,
quantitatively, behavioral patterns that occurred in each population
so that they could be compared to the population characteristics
already mentioned.
Observations of behavior were conducted under
laboratory conditions.
To measure agonis tic behavior (fighting activities), five,
one-quarter inch mesh hardware cloth cages (12 inches wide by 18½
inches long by nine inches high) were used to conduct behavior trials.
These chages held two adult males captured from the populations.
Figure 6 shows that these cages contained a hardboard partition to
create two equal sized compartments, and that a sliding door could
2L
Figure 6.
The dual compartment cage was divided by a partition
containing a hole and a sliding door through which
either mouse was able to cross to the opponents
side during a trial.
2
be removed to provide an opening between the two compartments. The
cages, when in use, always contained alfalfa, potato, and oats.
Adult mice were obtained from
the enclosures and the field plot
for observation in the dual compartment cage. Dual trials involved
combinations of non-dispersal and dispersal adult males from the
different population phases. Behavior data of all adult males
representing a particular population were grouped together to
provide
an indication as to the agonistic behavior patterns o± that population. Also, data for non-dispersal males and dispersal males were
separated for each enclosure population to show possible behavior
differences between these two types of voles.
After mice were brought into the laboratory for observation, one
of the individuals in each trial was fur clipped on the back for
identification.
The mice were left in their compartments over night
so that they would become accustomed to their own territory before
they were observed.
The trial began when each mouse was provided
access to the opponents compartment by the removal of the partition
door.
All trials lasted ten minutes, and at each ten second. inverval
the predominant behavior pattern of each mouse was recorded.
at the end of each trial there was an accumulation of' 60
activity patterns for each mouse on trial.
Thus,
recorded
A particular behavior
pattern was represented by the number of recorded ten second invervala
for that pattern.
Fighting time was measured by using a stop watch
to obtain the number of seconds of actual fighting.
All observations
were made from behind a canvas blind during the mid-day hours.
The
26
presence of the observer did not seem to disturb the mice.
Pertinent behavior activities summed up at the completion of
each trial were as follows:
1. The total seconds of fighting
2.
The total aggressive and total defensive fighting behavior
3. The total threat and total retreat behavior
i.
The total exploratory behavior
S.
The total active and total inactive behavior
6. The total washing arid grooming behavior
Active or inactive behavior was indicated when movement or no movement
occurred.
In a trial where conflict occurred, each mouse was recorded
as a dominant or subordinate if possible. This decision was based on
avoidance behavior, aggressive approaches, defensive and aggressive
Lighting postures, displacement activity patterns, and wounding. The
voles were returned to their respective trap station areas after
undergoing one
trial
per day £ or one or two days.
Observations were made on solitary voles placed in an arena.
It was expected that solitary behavior studies would disclose any
variation in behavior and movement patterns that may exist among
voles. All sex and age groups of voles were obtained from the
dispersal ramps and populations to observe their behavior under
solitary triaL ccrjtiona. The arena (36 inches wide, 21 inches
deep, and 22 inches high) had three blank plywood walls and a glass
front. The floor, covered with wood shavings, contained alfalfa arid
sliced potate during each trial. A trial consisted of placing a
27
mouse in the arena, waiting quietly for two minutes, and then
observing and recording the activity as in the dual trials,
The
patterns recorded were exploratory behavior, active behavior, inactiTe
behavior, and washing and grocing behavior.
After a behavior trial,
the mouse, except for a dispersal mouse, was returned to his original
point of capture.
RESULTS
The behavioral and pomlation characteristics for Znclosuree 1
to 7 and the Caledonia-6 plot obtained during the trapping months of
1963 arid l961 are presented here.
To aid in comparing enclosures
with populations stocked at the same time, Enclosures 1, 2, S, and
7 have been grouped separately from Enclosures 3, b, and 6 in moat
of the following tables.
Behavioral Characteristics
Agonistic Behavior Patterns of the Populations
The averages of fighting time, aggressive and defensive fighting,
and dominance and subordinance f or the populations having either
first year high densities, second year high densities, or third year
high densities are compared in Table XI.
Fighting time for adult
male mice of the first year high density populations, l7.
øeconda,
was longer than the fighting time for adult male mice of the second
and third year high density populations with 10.3 and 9.8 seconds,
respectively.
The aggressive fighting of mice was similar among
the three phase years, but the third year high density populations
did shcmr a slight increase of aggressive fighting (2.2) from the
previous year's aggressive fighting (l.). Nore mice displayed
dominance behavior in l96L than 1963.
Dominance was identified in
314 percent of the trials for mice from the third year phase
populations.
14,
populations phase year second for averages or total over-all The 2
activity indicated displaying trial in
interra second ten of number Indicates 1
23
29
314
23
28
23
10.3
9.8
1.9
22
2.3
1.6
76
89
112
128
19614
6d III and
Ill 3d, III
19&)
7 II and Sd, II
2d, II ld, II
2
1.7
10.3
1814
129
Ccmbiaed
14,
17
15
21
214
2.14
1.5
1.8
1.5
10.3
72
53
1963
6d II and
II 3d, II
Subordinance %
Dominance %
Fighting1 Defensive
Trials Number
93
Fighting Aggressive
Seconds in
Time Fighting
17.5
66
1963
5d I
7 I and
Mice Number
Patterns Behavior
2d, I Id, I
19614. AND 1963 FOR PHASES YEA.R DENSITI IIIGH TB1BD AND SECOND, FST, THE
REPRF3EW1ING POPULATIONS TIlE FOR SUBOROINANCE AND IXINANCE AND FIGHflNG, DEFENSIVE
AND AGGRESSIVE TD&E, F]OIftINO OF AVERAGES AND TRIAlS BEHA.VIOR WAL AND MICE TRIAL NUMBER
II. TABLE
The average dual trial behavior characteristics of adult male
mice from Enclosures 1 to 7 from June to October, 1963, are presented
in Table III.
The fighting time average for I 7 mice (33.5 seconds)
was the longest fighting time average for enclosure mice.
I 54,
II b, and I 24 mice bad fighting time averages of 15.9, 13.7, and 11.7
seconds, respectively.
These averages were similar to the over-all,
1963 fighting time average of 1)4.2 seconds.
II 64, I 14, and IX 3d
mice had the shorter fighting time averages of 10.b, 10.3, and 9.2
seconds, respectively.
I Sd and
I? mice exhibited more fighting
time than the other enclosure mice.
4ice from 17 and II)4 (no dispersal ramps) fought more per
trial than mice of their respective year phase. from enclosures with
dispersal ramps. I 5d, having a low dispersal rate and reaching a
high density, was characteristically similar to II b in behavior
patterns.
I ld, I 2d, II 3d, and II 6d mice showed less fighting
and were more aggressive than defensive in their fighting.
II 3d
and II 6d mice tended to show less exploratory behavior (10 and 1)4,
respectively) than I id and I 2d (2)4 and 17, respectively).
Ixploratory behavior
for II b, second year non-dispersal population,
was 9.5 which was low compared to other enclosures, except II 3d.
The average behavior characteristics of
adult male mice from
Enclosures 1 to 7 and the Caledor.ta-6 plot from June, through December,
196)4, are given in Table IV.
The fighting time
averages for II Sd
(12.6 seconds) and II 7 (11.5 seconds ) were longer than the over-all
1 O 7 FRC
JUNE THROUGH OOBER, 1963.
Total or
I id
I 2d
I Sd
I 7
U 3d
II b
II 6d
Number Mice
3.3
23
16
L1.
22
6
25
119
Number Trials
18
32
21
22
31
9
32
165
Fighting Time'
Seconds
2
Aggressive Fighting
10.3
11.7
15.9,
33.5
2.7
2.b
.6
b.i
1.
.7
Lb
2.6
2.?
1.2
1
.9
2.1
2.?
Behavior Patterns
Defensive Fighting2
Threats2
1
Retreats2
% Dinance
% Subordinance
cp1oratory2
Active2
InactIve2
.7
3.b
Average
lb.2
13.7
10.li.
.7
Lb
1.5
2.6
.9
1.6
1.6
1.3
1.3
Lb
.6
1.6
1.8
9.2
1
2
22
10
32
19
0
16
20
5
3.9
23
37
13
33
16
19
2b
17
13.5
15
10
lb
15
19
19
20
19
28
22
22
20
5
13
17
12
18
1?
lb
lb
3
9.5
Washing2
5.b
b.3
2.9
b.7
S.b
5.6
1 lb.2 . 3.7 confidence interval at five percent significance
2 Indictes number of ten second intervals in trial displaying indicated activity
b.b
TABLE IV.
AVERAGE CHARA.CTERISTICS OF ADULT MALE MICE FRC ENCLOSURES 1 To 7
AND THE CALEDONIA-6 PLOT FR( JUNE TO DECEM3ER, 196b.
Behavior Patterns
II id II 2d II 5d II 7 III 3d III
14.
III 6d
Total or
Cal.-6
Average
Number Aice
17
19
22
18
21
31
3h
165
17
Number Trials
25
26
32
29
142
143
143
2140
28
12.6
11.5
U
.8
1.8
2.5
2.5
2.14.
Fighting Timed-
9.5
7
9.L
9.1
'10.0
3.5
2.2
1.7
2.5
2.1
1.1
23
2
1.5
1.14
2
1
1
1
.8
1.3
2.3
1.6
1.2
1.7
Sec ond8
Aggressive Fightin2
2.6
Defensive Fighting2
2
Threats2
1.li.
.8
2.1
2
Retreats2
1.5
1.2
1.6
1
Dominance
14.0
Ii.
Subordinance
214.
Exploratory2
Active2
%
Inactive2
Washing2
1 10.0 +
2
.5
1.2
314.
38
33
26
14.2
33
7
38
28
21
31
16
23
26
18
23
20
19
16
20
18
20
20
19
21
21
21
23
20
20
21
21
20
6
13
8
11
11
13
10
11
11
2.8
2.8
3.2
2.5
1.14
2.6
2.5
3.14
1.5 Confidence Interval at five percent significance
Indicates number of ten second intervals in trial displaying indicated activity
3.14
33
1961 Lighting time average (10.0 seconds).
III 3d had the third
, and
longest Lighting time average, 11 seconds, then II id, III
UI 6d followed with averages of 9.5, 9., and 9.1 seconds,
respectively. U 2d and Caledonia-6 plot mice had short fighting time
averages of 7.0 and 3.5 seconds, respectively. lU 3d was the only
enclosure that exhibited more fighting in 196b than in 1963.
Fighting time for III 1 was similar to dispersal ramp enclosures,
except II Sd.
III 3d, III
respectively.
In 196b, aggreaavo fighting generally increased for
, II Sd, and III ád with 2.2, 1.7, 1.8, and 2.5,
Aggressive fighting decreased fox' II 2d (.8) and
(2.5) and did not change for U ld (2.6) in 1961i..
Both III )
II 7
and
II 7 showed slightly less exploratory behavior (18 end 16, respective-
ly) then the five diepeal ramp enclosures *
Caledonia-6 plot mice from a low density and showing little
fighting time (3.5 seconds), displayed less aggreesve (1.1) and
defensive (1.0) fighting than the enclosure averages.
These mice
exhibited more threat (2.3) behavior in general than mice from the
high density enclosures.
In rnwmiary, the average fighting time for the first year
populations was longer than that of the second year populations
and still longer than that of the third year populations.
The
third year high density populations showed a slight increase of
aggressive fighting over the previous year.
Dominance behavior
was identified more times in 196b populations than in 1963
populations.
This suggests that mice of populations in 1961i
3L$
may have established better social relationships within their
populations.
Mice representing non-dispersal enclosures displayed
more fighting behavior than mice from dispersal enclosures of their
respective year phase, except in the third year phase.
Exploratory
behavior for the second and third year non-dispersal populations
was less cc*muon than the respective dispersal populations of the
same year phase.
The low density plot population exhibited lees
fighting behavior and more threat behavior than the high density
enclosure populations.
Non-dispersal Mice Compared to Dispersal Nice
The average agonistic behavior characteristics for adult male
non-dispersal mice and adult male dispersal mice from I id, I 2d,
I 5d, II 3d, and II 6d from June to October, 1963, are given in
Table V.
The over-all averages of non-dispersal and dispersal
trial mice show that fighting time for non-dispersal mice was
significantly longer at 13.2 seconds than the average of 8.3
seconds for dispersal mice.
The aggressive fighting (2.2) and
defensive fighting (1.7) for non-dispersal mice were greater than
the aggressive fighting (1.0) and defensive fighting (1.0) for'
dispersal mice.
The average percent dominance (26) for non-
dispersal mice was larger than the nine percent average for
dispersal mice,
To conclude, the 1963 non-dispersal mice fought
more, were more aggressive than defensive in their fighting,
and displayed a higher percent of dominance than dispersal mice.
TABLE V.
AVER&GE AGONISTIC BEHAVIOR CHARACTERISTICS FOR AI1JLT MALE NON-DISPEIAL
5, 3, AND 6 RC1 J1JN THROUGH OCTOBER, 1963.
AND DISPERSAL NICE 1RC}I ENCLOSURES L,
Behavior Patterns
Non-dispersa1 Nice
Number Mice
Number Trials
Fighting Time1
Aggressive Fighting2
Defensive Fighting
% Dominance
% Subordinance
Dispersal Mice
Number Mice
Number Trials
Fighting Time3
Aggressive Fighting2
Deferive Fighting2
%Dominance
% Subordinare
I 2d
I id
6
9
10.1
3.8
0
145
0
-
22
11.8
i7
10.5
1.3
L3
.8
22
11
30
10
II 6d
Average
or Total
114
12
514
2
214.2
10.14
.6
2.14
16
12.5
2.3
82
13.2
2.2
1.7
26
16
2
18
23
II 3d
12
8
114
9
10
11.7
2.2
7
9
I Sd
14.14
.9
1.14
17
33
26
9
31
13
8
8
9
8
13
16
14.14
5.5
8.14
.14
.5
.8
.6
.1
0
11
1.8
0
25
145
0
19
52
8.3
1
1
9
15
1 13.2 + 5.1 Confidence intervals at five percent significance
Indictes number o± ten second intervals in trial displaying indicated activity
2
3 8.3+ 14.3 Confidence interva1 at five percent significance
'It
36
Non-dispersal and dispersal mice of I 14, I 2d, and I 54
varied in their agonistic behavior patterns.
Fighting time in
I 14 and I 2d far the two types of mice were similar, and I 24
dispersal mice displayed more aggressive fighting than nondispersal mice.
fighting.
I Sd non-dispersal mice had a very high rate of
The non-dispersal mice in II 3d and II 64 were constatent
in exhibiting more fighting, aggressiveness, and dominance than
dispersal mice.
The average agonistic behavior characteristics of adult male
non-dispersal mice and adult male dispersal mice from II 14, II 24,
U Sd, III 3d, and III 64 fran June to December, 19614, are given in
Table VI.
The over-all fighting time average for non-dispersal
mice (10.7 seconds) was a little higher than the average (9.8
seconds) for dispersal mice.
Aggressive fighting (2.1) was similar
o defensive fighting (2) for non-dispersal mice.
The aggressive
fighting (1.9) for dispersal mice was slightly less than defensive
fighting (2.1).
Dominance (35 percent) was again higher for non-
dispersal voles than the dominance (214 percent) for dispersal voles,
The over-all 19614 agonistic behavior averages for non-dispersal
and dispersal mice show that non-dispersal mice were slightly more
aggressive, more dominant, and only fought slightly longer than
dispersal mice.
II 14, II 24, and II 5d characteristics for the non-dispersal
and dispersal mice were inconsistent.
II ld and II 24 dispersal
mice had higher fighting time averages than non-dispersal mice.
TABLE VI.
AVERAGE AGONISTIC BEHAVIOR CHARACTERISTICS FOR ADULT MALE NON-DISPERSAL AND DISPERSAL
NICE FROM ENCLOSURES 1, 2, 5, 3, AND 6 FROM JUNE THROUGH DECEMBER, 196)4.
Behavioral Patterns
Non-dispersal Mice
Number Mice
Number Trials
Fighting Time1
Aggressive Fighting2
Defensive Fighting2
% Dominance
% Subordinance
Dispersal Nice
Number Mice
Number Trials
Fighting Time3
Aggressive Fighting2
Defensive Fighting2
% Dominance
% Subordivance
1
2
3
II id
II 2d
II Sd
III 3d
III 6d
10
11
13
5.4
18
21
37
24
12.6
1.7
11.5
2
1.9
10.2
2.7
1.7
47
17
6.9
1.9
1.5
35
24
7
8
14.9
3.6
2.9
So
25
.6
2.2
0
38
8
13
11.6
1
2.7
8
38
26
2.5
35
27
38
30
4
6
3
12.7
2.2
2.2
33
33
30
5
7.5
.2
Total or
Average
84
123
10.7
2.1
2
27
35
28
10
13
7.3
2.2
32
45
9.8
1.9
.9
2.1
24
29
2.2
0
31
40
15
10.7+2.2 Confidence interval at five percent significance
Indicates number of ten second intervals in trial displaying indicated activity
9.8+3.4 Confidence interval at five percent significance
Essentially there was little difference in II d between the behavior
of non-dispersal mice and dispersal mice, for both had equally high
rates of fighting behavior.
The fighting time of non-dispersal mice
of II Id, II 2d, and II Sd decreased from higher averages in 1963,
and fighting time for dispersal mice of II Id and II Sc! increased
from lower averages in 1963.
The III 3d and III 6d fighting for
non-dispersal mice was greater than that for dispersal mice.
In summary, the agoniatic behavior averages for 1963 nondispersal and dispersal mice show a greater difference and less
variation than the averages for non-dispersal and dispersal mice
of 19614.
In general for 1963, non-dispersal mice exhibited a
stronger tendency for fighting behavior than did dispersal mice.
Solitary Behavior Patterns
The exploratory, active, inactive, and washing and grooming
solitary behavior characteristics for dispersal mice oi I id,
I 2d, I Sd, II 3d, and II 6d and for non-dispersal mice from June
through October, 1963, are presented in Table VII.
Exploratory
behavior for dispersal mice from ramps of I id, I 2d, and I Sc! was
slightly higher at 38, 141, and 39, respectively, than that for II 3d
and II 6d dispersal mice at 31 and 36,, respectively.
Mice from the
five dJ.spe a? :ap exhibited similar active behavior.
Inactivity
varied throughout the ramps with Ramp 1 at 0.14 and Ramp 3 at 9.0.
Washing behavior was inconsistent *
EXPLORATORY, ACTIVE, INACTIVE, AND WASHING AND GROOItENG SOLITARY BEHAVIOR CHARACTERISTICS
FOR DISPERSAL 1IOE CAPTURED IN RAKPS 1, 2, 5, 3, AND 6 AND FOR NON-DISPERSAL MICE FROM
THESE ENCLOSURES DURING JUNE THROUGH OCTOBER, 1963.
TABLE VII.
-
Behavior Patterns
Ramp I 1
Ramp I 2
Ramp I 5
Ramp II 3
Ramp II 6
Average
Non-dispersal
Exploratozy1
38
hi
39
31
36
36
25
Active1
i)
12
12
13
16
13.7
21
.5
3.1
1.8
9
2.5
8.2
3.6
7.7
7.3
3.9
inactive1
Washing1
Numuer Mice
1
3.0
10
6
16
6
5.9
16
7.3
22
Indicates number or ten second intervals in trial displaying indicated activity
'0
The exploratory, active, inactive, and washing and grooming
solitary behavior characteristics of dispersal mice of II id,
II 2d, II Sd, III 3d, and III 6d from June to December, 196h, are
presented in Table VIII.
Voles from Ramps 1, 2, and
continued
to exhibit higher exploratory rates of 1l, hO, and 38, respectively,
than Ramps 3 and 6 at rates of 27 and 36, respectively.
Exploratory
behavior patterns remained similar to the previous year's.
Active
behavior was similar among the ramps
Non-dispersal mice obtained from these five dispersal enclosures
in 1963 showed less exploratory (25) and more active (21) behavior
than dispersal mice.
A high number of inactive (6.0) and washing
(7.3) behavior patterns were exhibited by non-dispersal mice.
In summary, slightly more exploratory behavior was displayed
by voles from Ramps 1, 2, and 5 in 1963 and 196h than in Ramps .3
and 6.
Solitary behavior patterns for dispersal mice of II Id,
II 2d, II Sd, and III 6d showed little change in 196h.
The
exploratory behavior patterns for dispersal mice showed no apparent
relationship to population phases.
Non-dispersal mice showed less
exploratory behavior and more active behavior than dispersal mice.
Population Characteristics
Trapping Periods
The populations were not trapped at the seine time, and to
assist in analysis the trapping periods are given designations.
TABLE VIII.
EXPLORATOaT, ACTIVE, INACTIVE, AND WASHING AND GROOMING SOLITARY BEHAVIOR CHARACTERISTICS
OF DISPERSAL MICE FROM RAMPS 1, 2, 5, 3, AND 6 THROUGH JUNE TO DECEMBER, 196)4,
Behavior Patterns
Ramp II 1
Ramp II 2
Ramp II 5
Ramp III 3
RampIII 6
Average
Exploratory'
lii
hO
38
27
36
38
Active1
1)4
13
15
17
1)4
1)4
Inactive1
2.3
.8
2.2
9.2
)4.3
ashiQ-
2.8
6.2
b.8
6.8
5.8
liumber Nice
3.
18
12
11
6
12
Indicates, number of ten second interva1s in trial displaying indicated activity
3
Trapping periods for I id, I 24, and II 3d studied from June, 1963,
through January, 19614, are shown in Table IL.
In 1963, the trapping
periods for I 5d and I 7 were similar to I Id and I 24, and
trapping periods for II
14
and II 64 were similar to II 3d.
Smith
(19614) has presented the exact dates for II 14, I Sd, II 64, and
In the second year of study the seven enclosures and the
I 7.
Caledonia-6 plot were trapped approximately once a month from
I4ay to
cernber, 1614. The trap months and dates are presented in
Tables X and XI for II 14, II 2d, II
d, and II 7, and for III 3d,
III 14, III 64, and Caledonia-6 plot, respectively.
Population Densities
The total number of Microtus captured, the population estimate
with two standard errors, the density per acre, and the number dead
in the traps for each trap period of the 1963 and 19614 populations
are given in Table XII and Table XIII, respectively.
The comparison
of populations are mainly based upon the population estimates.
Population eat1inates for the seven enclosures in 1963 increased
gradually from June to October and reached peak densities in November
or December.
1 ld, I 2d, I Sd, and I 7 produced peak population
estimates of 199, 230, 3145, and 1409 mice, respectively.
The pop-
ulations of II 3d, II 14, and II 64 reached peak estimates of 229,
269, and 295 mice, respectively.
The average of peak population
estimates for I id, I 24, I 54, and I 7 was 295, and the same average
TABLE IX.
TRAP PERIOD DESIGNATIONS FOR I Id, I 2d, AND II 3d FROM JUNE, 1963, THROUGH
JANUARY, 196L
Designation
lid First Year High DensityI2d
Second Year High Density
113d
June
June 25-29
June 25-29
June J-6
July
July
July 15-18
July 9-12
August 13-17
August 6-9
August
-
August
I
II
August 13-17
August 27-29
September
- 1
September
-
October
I
-
15-18
II
September L-6
September )-6
September 23-27
September 23-27
October 15-17, 19
October 15-1?, 19
October - II
September 17-21
October 9-12
October 29-31
November 2
November
November 5, 7, 16
November
December
December 18-21
December 18-21
January
5,
7, 16
November 20-23
January 11v17
TABLE L TRAP PERIQD DESIJNATION FOR II 1d
Designation
II id
May
July
Augzst
September
October
II 2d, II Sd, AND II 7 FROM M1Y THROUGH DEOEM]3EF, 1961.
Second Year High Density
II 2d
II Sd
Nay 26-29
Nay 26-29
May 19-22
May 19-22
July 2i-2L.
July 21-2Li.
June 30
-July 3
July 17-18
Mgu.st 17-20
August 17-20
August i-7
August U-i!
September 22-25
September 29-October 2
September 1-14
September 15-18
October 27-30
October 27-30
October 7-10
October 20-23
November 17-20
November 23-26
November
December
II 7
December 8-il
December 8-11
TABLE XL TRAP PERIOD DESIGNATION FOR III 3d, III 14, III 6d, AND ThE CALEDONIA-6 PLOT FR
NAT THROUGH DECEMBER, 19614.
Designation
III 3d
Third Year High Density
III 14
III 6d
Low Density
Galedonia-6
May
Nay 26-29
May 19-22
Nay 19-22
July
July 21-2
June 30
-July 3
July iS-18
July 1S-18
August
August 17-20
August 14-7
August U-114
August 11-114
September
September 29
-October 2
September 1-14
September 1-l8
September 22-2
October
October 27-30
October 7-10
October 20-23
October 20-23
November 17-20
November 23-26
November 2L-26
December
December 8-11
TABLE XII.
136
TOTAL NICE CAPTURED, POPULATION ESTIMATE, DENSITY PER
ACRE, AND THE NUMBER DEAD LN TRAPS FOR ENCLOSURES 1, 2,
5,
Trap Period
Designation
7,
3, 13, AND 6 FROM JUNE, 1963, TO JANUARY, 19613.
Total
Captured
Population Density
Estimate
Per Acre
Dead in
Traps
I id
Jme
July
113.
August
313
September-I
September-Il
October
9
November
53
92
107
136
December
9+1*
36
1
152
395
60
0
156
1
92+12
260
368
0
0
658
15l19
6013
0
19925
796
119
1131+18
5613
0
1
July
8
21
8+0
32
0
August
2l'3
84
1
36t
36j-5
1134
135
557
220
372
I 2d
Jrne
September-I
September-lI
October
83
November
130
169
December
92
93+12
156+20
230+29
9212
13
3
0
5
624
920
368
2
5
5
15d
June
July
August
September-I
September-Il
October
November
December
January
Li.
June
13+13
153
52
113
2f$
27+6
25
265
519
60
106
104
137
68
94
8i1812229
0
0
0
201j.
324
1386
.
0
0
0
3.,
1
0
255
3135+54
34
137+22
5
5+0
190
20
76
39+7
156
0
3
1,380
186
0
July
19
August
September-I
38
132
50113
200
0
September-lI
October
November
December
J
63
711S
9851
i85Th1
2813
2
76
134
2136
1309813
136
8252
392
2
1130
5
1,636
326
0
0
b7
TABLE XLI CONTINUE,
Trap Period
Designation
Total
Captured
Population Density
Estimate
Per Acre
Dead in.
Traps
II 3d
Juno
July
8
8+0
35
bOS
32
160
0
2
2
0
August-I
August-Il
69
7b
8311
8110
332
September
October-I
October-lI
November
January
116
153
13317
202
22929
20426
532
76b
916
816
b28
1
0
173
88
191+21i.
l07114
32h
S
1
2
'lb
July
August
September-I
September-Il
October
November
December
January
II
9
27
9+0
30'8
36
397
ho
57
hh+9
71
205
62+10
81+17
269Th3
59
618
36
0
120
156
176
0
0
218
2
1
32L1.
1,076
276
1
28
0
3
6
irluLy
August
September-I
September-Il
October
7
29
70
3717
h9
ib.8
2
0
Novsiber
1
80
117
123+17
165
December
19527
180
36b
h96
780
210
83
295'53
1,180
0
b60
0
January
* To standard errors
9118
1135
3
10
2
48
TABLE XIII.
TOTAL ?aCE CAPTURED, POPULATION ESTIMkTE, DEflBITY PER
ACRE, AND ThE NUMBER DEAD
FOR ENCLOSURES 1
THROUGH 7 AND FOR CALEDONIA-6 PLOT FROM NAY THROUGH
DECEMBER, 1964.
IN 9S
Trap Period
Designation
Tota].
Captured
Population Density
Per Acre
Estimate
Dead in
Traps
II ld
May
July
August
September
October
December
II
48
111
111
80
68
70
6422*
13630
256
20839
834
103+28
82+21
544
1413
8622
329
345
0
0
0
6
0
0
2d
3012
1.0
0
102+24
122+24
407
488
10
73
65
98+18
426
392
92+17
367
C)
24
25+2
100
0
August
September
October
69
8221
327
S
147
121
886
11
760
0
90
22244
190+42
10722
427
2
November
47
6020
238
1
80
0
May
July
August
September
October
December
24
88
101
84
10723
0
0
0
II 5d
May
July
II 7
May
July
August
September
October
November
18
117
153
119
83
56
20+5
15938
21249
161+30
9215
5810
638
S
848
646
368
230
22
0
0
0
TABLE XIII CONTINUED.
Trap Period
Designation
Total
Captured
Population Density
Estimate
Per Acre
Dead in
Traps
III
May
July
August
September
October
19
59
65
71
i;i
6J!l2
76
0
2h1..
2
70114,
280
2
87+2b
350
332
1
0
520
2
68
69
83
83+20
130+26
May
16
17+)4
July
63
136
118
December
III
August
September
October
November
73
59
812.
325
0
0
2290
15123
915
13
603
Ii.
3
3
369
3
72
0
0
13
96+32
92+20
III 6d
May
17
July
August
106
123
September
October
November
103
80
71
18+L
1520
608
1h93!.
13+38
596
571j.
1
95+21
379
5820
230
1
0
12+18
60
L0
0
140
1
Gale donia -6
July
9
August
September
October
6
7
13
November
18
* Two standard errors
8+8
8+i
21+10
26+16
0
1014.
2
130
0
for II 3d, II lj, and II 6d was 26ii.
Smith (196i) found that the
peak density of I? (E 7) was significantly higher than that of II
(E !t).
For first year populations, peak densities were generally
lower in enclosures with dispersal ramps than in I 7 which had none.
In 19614, populations in II id, II 2d, II
d, and II 7 rapidly
increased in numbers from May through August when peak estimate8
reached 208, 122, 222, and 212 mice, respectively.
The population
estimates of these four enclosures gradually declined for the three
trap periods following August.
More variation existed in the peak
density periods of III 3d, III 14, and III 6d.
III 3d had a high
population estimate of 130 mice in December while III
14
climbed to
a high of 229 mice in August, and III 6d. reached a peak in July at
1S2 mice.
The average of peak population estimates for II id,
II 2d, II Sd, and II 7 was 191, and the same average for III 3d,
III 14, and III 6d was 170. lU 3d and III 6d had lower densities
than III i
Caledonia-6 plot continually produced low population estimates
ranging from 8 to 26 (140 to 130 per acre) with the high in November.
In swmiary, high population estimates, in 1963, were reached
by November or December in Enclosures I to 7.
1 ld, I 2d, I Sd,
and I 7, in their first year of high densities, contained higher
average densities than the populations in II 3d, II 14, and II 6d
in their second year of high densities.
The peak density of I 7 was
significantly higher than that of II 14.
Peak densities for 19614
5]-
populations, except III 3d, were reached mainly in August, and
afterwards numbers declined through late summer and fall.
III 3d,
III b, and III 64, in their third year of high densities, produced
a lower average peak density and more variation in peak density
periods than II id, II 24, II Sd, and IX 7 in their second year of
high densities.
Peak densities were generally lower where
dispersion was allowed than where dispersion was not allowed, except in I]: Sd and Ii 64.
Sex and Age Composition
The sex and age composition for I 14, I 2d, and II 3d are
presented in Table XIV. Sex and age data for II b, I Sd, II 64,
and I 7 (E 1, E 5, E 6, and E 7) has been presented by Smith (1961i).
Males were more numerous in II 1
and I 7 until October and September.
In I 14, I 24, II 3d, I 54, and II 64, containing dispersal ramps,
females were more numerous until November or December when males
become more numerous.
Higher percentages of adult mice, 75, 77, 70,
and 73, were present in 1 24, II b, II 64, and I?, respectively,
than in I id, II 3d, and I 54 'with )7, 65, and 62 percent, respectively.
The percentage of adults, number of males and females, their
means, and the sex ratios for Enclosures 1 to 7 and for the Ca].edonia6 plot from May through December, l96b, are shown in Table XV.
II 24
and III 64 had higher numbers of females than males compared to the
other five enclosures.
The average percent of adults in the
TkBLE XIV.
52
PERCENTAGE OF ADULTS, NUMBER OF MALES AND FEMALES, THEIR
MEANS, AND THE SE.X RATIOS FOR I id, I 2d, AND II 3d,
FROM JUNE, 1963, TO JANUARY, 196!.
Trap Period
Designation
Percent
Adults
Number
Males
Number
Females
Sex
Ratio
lid
June
July
August
September-i
September-Il
October
November
December
Mean
22
50
65
66
7S
62
53
6
14
5
11,
7
20
22
36
31
56
50
68
72
Li
7
7
66
147
80:100
100:100
70:100
71:100
614:100
88:100
103:100
153:100
36
I?d
Juno
July
August
September-I
September-Il
October
November
December
Mean
Ii 3ô
June
July
August-I
August-lI
September
October-I
October-lI
November
January
Mean
5
11
75
95
72
80
72
6
10
15
20
32
614
72
51
76
97
77
148
1414
7
31
1l
3
514
21
25
63
2
6
6:
13
35
33
22
58
59
51
63
53
77
98
65
149
71
95
85
314
67
79
107
88
1414
147
514
60:100
91:100
71:100
80:100
63:100
71:100
714:100
108:100
33:100
59:100
103:100
80:100
73:100
914:100
89:100
96:100
100:100
53
TABLE XV.
PERCENTAGE OF ADULTS, NU)ER OF MALES AND FEMALES,
THEIR MEANS, AND THE SEX RATIOS FOR ENCLOSuRES 1
TO 7 AND FOR CALEDONLt-6 PLOT FROM MAX TO DECEMBER,
19614.
Trap Period
Designation
II id
Ma
July
August
September
Percent
Adults
Number
Males
Number
Females
Sex
Ratio
85:100
72:100
122:100
67
73
22
26
146
614
149
61
Ii).
147
50
33
82
98
39
December
Mean
68
142
May
July
August
September
75
69
16
8
32
56
148
147
514.
32
39
14$
October
614
1
32
Deceiiber
95
Mean
614
29
31i
35
Hay
July
August
87
75
8
16
35
85
314
1.41
September
October
28
52
61
39
60
137:100
102:100
November
Mean
83
61
Si
20
77:100
135:100
142
May
July
August
September
October
November
Mean
61
67
8
10
1414
60
93
73
60
80:100
60:100
155:100
145
614
1iS
1142:100
72
143
14.0
100
67
28
28
October
32
J2
1142:100
122:100
109:100
39
II 2d
27
147
62
1
200:100
57:100
87:100
87:100
128:100
80:100
50:100
103:100
106:100
100:100
514.
TABLE XV CONTINUED.
Trap Period
Designation
Percent
Adults
Number
Males
Number
Females
Sex
Ratio
III 3d
May
July
August
September
October
December
Mean
100
66
38
72
9
26
38
140
714
36
51
33
914
6
714.
31
75
91
10
33
37
31
33
32
90:100
79:100
103:100
129:100
109:100
159:100
29
III 14
May
July
August
September
October
November
Mean
59
131
56
80
67
80
78
).7
33
146
10
32
56
52
37
26
35
60:100
97:100
1143:100
150:100
127:100
127:100
ILL 6d
May
July
August
September
October
November
Mean
Caledonia-6
JUly
August
September
October
November
Mean
76
75
60
36
59
91
66
78
16
100
69
89
70
60
11
60
63
149
514
33
35
38
147
6
146
6
2
14
3
5.6
76:100
95:100
91:100
70:100
97:100
15
7
2
7
8
514:100
14
6
10
5.0
350:100
50:100
133:100
116:100
80:100
55
enclosures, except III 3d, ranged frcei 61 to 68.
The average percent
of adults in III 3d was slightly higher at Th.
The Oaledonia-6 plot popx1ation averaged 70 percent adults and
showed considerable variation in the sex ratio.
In summary, a larger number of females were present until
November or December in the 1963 populations having a means to
disperse.
I 2d, II l, II 6d, and I 7 had higher percentages of
adults than I id, II 3d, and I 5d.
Males were slightly more
numerous in the populations, except II 2d and III 64, for 196b. III
d
had slightly higher peràentages of adults than other 196I populations.
Reproduction
The number of sub-adult and adult females and percentages of
these females perforate, pregnant, or with mammary glands large or
lactating, and their means for Jnclosures 1 through 7 frc
July to
late November or December, 1963, are presented in Table XVI.
The
enclosure populations exhibited good reproductive rates through
October.
Scrotal malee were abundant throughout the enclosures
frcm June to November.
1 id, I 2d, and II 3d showed the lower
mean percentages forfemales perforate, 37, 38, and 36percent,
respectively. The mean percentages of females pregnant for I id
and II 3d, 21 and 16 percent, respectively, were similar to their
corresponding mean percentages of females with large or lactating
manunary glands, 20 and 17 percent, respectively.
This suggests
TABLE XVI.
56
NUMBER OF SUB-ADULT AND ADULT FEMALES AND PERCENTAGES
OF THESE FEMALES PEPORATE, PREGNANT, OR WITH MAMMARY
GLANDS LARGE OR LACTATING, AND THEIR MEANS FOR
ENCLOSURES 1 THROUGH 7 FROM JULY TO NOVEMBER OR
DECEMBER, 1963.
Trap Period
Designation
Niber
Females
Females
Perforate
Females
Pre$nant
}famia
Glands
Large or
Latating
I id
July
August
September-I
September-Il
October
November
December
Mean Percent
I 2d
July
August
September-I
September-Il
October
November
December
Mean Percent
7
29
19
57
28
67
51
61
hi
15
7
11
19
22
b9
71
92
29
21
35
31
25
6
2
29
16
11
31
11
0
20
37
21
6b
b7
50
53
b6
36
21
31
20
20
0
0
13
18
19
18
lb
25
35
21
21
27
0
8
2
8
36
5
9
0
15d
8
August
September-I
September-lI
October
November
December
Mean Percent
lb
16
33
b6
62
127
65
50
68
57
Sb
2
0
12
12
13
10
1
1
b7
19
ho
67
60
17
93
60
hI
25
6
8
20
13
22
8
18
l.7
LfJ
17
July
August
September-I
September-Il
October
November
December
Mean Percent
5
12
23
3b
U6
79
118
0
20
0
0
11
2
l0b
57
TABLE XVI CONTINUED.
Trap Period
Number
Designation
Females
II 3d
July
August-I
August-Il
September
October-I
October-Il
*November
Mean Percent
21
32
37
51
75
99
88
Females
Perforate
67
Females
Pregnant
1)4
13
Nanmary Glands
Large or
Lact.ting
33
19
16
5)4
)40
L.9
35
2)4
21
7
8
0
0
16
19
6
6
36
1
17
II 1
July
Aagust
September-1
September-Il
October
November
December
17
67
88
65
16
9)4
27
7)4
)43
7)4
88
17
69
0
30
0
13.5
5
80
75
80
87
60
29
0
31
32
33
20
20
8
4ean Percent
II 6d
July
August
September-.I
September-Il
October
November
December
Mean Percent
*
Late November
33
13
0
33
38
30
50
29
28
3
16
25
39
55
83
9)4
7
60
6
0
17
13
22
1)4
19
0
13
29
12
7
1)4
58
that the reproduction that did occur within these two populations,
I id and. II 3d, was successful.
Smith (196ii) found that II h CE b) had better over-all
reproductive rates than II 6d (E 6), I Sd (E 5), and I 7 CE 7).
II 6d (E 6) showed slightly higher reproduction than I Sd (E 5)
and I 7 CE 7) (Smith, 19614).
II
14
The data of Table XVI indicates that
and II 6d had higher mean percentages for perforate females,
68 and 60 percents, respectively, than did I 5d and I 7, both at
II
147 percent.
14
females had the highest mean pregnancy rate
(30 percent) for the enclosures.
The mean percentages for pregnant
females for I Sd, I 6d, arid I 7 were similar at 19, 18, and 17
percent, respectively.
I Sd and, especially, II
14
mean percentages
for females with large or lactating mamary glands, 6.8 and 13.5
percent, respectively, were lower than their respective mean
percentages of females pregnant.
This suggests that prenatal
mortality was higher for these two enclosures than the other
enclosures.
Smith (19614) showed that prenatal mortality was more
cmnon for II
14
(E 14) than I 5d, I 7, and II 6d (E 5, E 7, and
E 6, respectivoly).
The nwaber of sub-adult and adult females and percentages of
these females perforate, pregnant, or with mammary glands larger
or lactating, and their means for Enclosures 1 through 7 and the
Caledonia-6 plot from May to December, 19614, are presented in
Table XVII.
The over-all reproductive performance for 19614 was
59
NUNBER. OF SUB-ADULT AND ADULT FEMALES AND PERCENTAGES
OF THESE FEMALES PERFORATE, PREGNANT, OR WITH MA1MARI
GLANDS LARGE OR LACTATING, AND THEIR MEANS FOR
ENCLOSURES 1 T}LWUGH 7 AND THE CLAEDONIA-6 PLOT FROM
NAY TO DECEMBER, 196b.
TABLE XVII.
Trap Period
Designation
II id
May
July
August
September
October
December
Mean Percent
Number
Females
21
60
b5
33
32
32
Females
Perforate
72
20
33
18
50
l
Li.O
Females
Pregnant
% Manunary Glands
Large or
Lactating
10
2b
b8
0
0
0
0
0
2.2
3
3
0
12
II 2d
May
July
August
September
October
December
Mean Percent
7
Sb
b14
32
36
71
35
36
18
25
17
0
6
0
0
0
0
0
0
0
0
0
1
2
.3
II Sd
May
July
15
August
September
October
November
Mean Percent
Sb
53
29
51
20
60
7b
bo
20
27
b7
38
2
o
0
0
0
0
0
0
38
8
14
67
62
50
31
30
17
15
0
33
0
0
0
0
25
33
2
II 7
May
July
August
September
October
November
Naan Percent
6
68
52
45
40
28
lb
21
2
0
0
9
TABLE XVII CONTINUED.
Trap Period
Designation
III 3d
May
July
August
September
October
December
Mean Percent
Number
Females
10
32
314.
30
33
32
Females
Perforate
Females
Pregnant
80
70
147
114
56
57
27
6
3
0
0
0
15
Nainary Glands
Large or
Lactating
50
28
12
13
27
22
II14
May
July
10
August
September
October
November
Mean Percent
51
20
86
39
148
1414
28
10
39
0
20
29
25
8
0
0
0
140
8
10
90
SLi.
69
So
18
53
52
147
142
50
23
0
0
147
314.
2
14
36
16
0
12
13
37
26
143
2
3
0
13
III 6d
Hay
July
August
September
October
November
Mean Percent
Caledonia-6
July
August
September
October
Novembor
Mean Percent
50
2
14
3
5
10
50
75
33
140
20
0
0
0
0
0
0
7
0
0
0
0
33
10
8.6
L
61
lower than that in 1963..
Scrotal males were numerous in all
enclosures from May through October.
Although poorer reproduction
was evident, the percentages for females perforate indicated that
the potential for reproduction exi.sted,
The enclosures showed
slight differences in reproductive percentages.
the lowest reproductive rates
II 2d exhibited
Table XVII indicates that III 3d
and III 6d had slightly better roproductioi than the other enclosures.
III 3d and III 6d populations displayed the higher percentages of
perforated females, l6 and O percent, respectively, and the higher
percentages for pregnant females, ih and 12 percent, respectively.
The occurrence of females with mammary glands large or lactating
indicated that pregnancies were generally successful for the l961.s.
enclosures.
The Caledonia-6 plot continually possessed females in
perforate condition, but pregnant females wore not found, arid only
two females possessed large or lactating mammary glands.
Scrotal
males were caught on thts plot throughout the study year.
In summary, voles in breeding condition were captured throughout
th
trapping periods for the 1963 and l96LL enclosures.
success was good in I 14 and I 2d.
than II 64, I
d, and I 7.
than that o± I Sd and I 7.
Reproductive
II 1 showed better reproduction
II 64 reoduction was slightly better
A high rate of prenatal mortality has
been suggested to have occurred in the II 14 population.
reproduction for the enclosures declined in August.
During 19614,
III 3d and III 64
showed slightly higher reproductive rates than other 19614 enclosures,
and II 2d exhibited the lowest reproductive rates. No pregnant
females were captured on the Qaledonia-6 plot.
General Survival
Survival rates of Mierotus captured in I ld, I 2d and II 3d
frcei June through December, 1963, are given in Table XVIII.
Smith (l961) has analyzed the survival rates of II i, I
and I 7 (E 1, E S, E 6, and E 7) for 1963.
d, II 6d,
1 ici had poorer survival
through October than I 2d and II 3d, but the November and December
cohorts among these enclosures were similar.
better over-all survival than I d and I 7.
II !. and II 6d had
Survival data
relationships between II 3d and first year populations were
inconsistent. For January, II 3d had higher percent survival rates
than I Sd or 17. Through November, I 5d and I 7 had better
survival than II 3d, except May and June cohorts in I 7.
Juveniles
had generally good survival In all enclosures through August.
Adults
and sub-adults survived best frc*u August to December.
Survival rates for the different age classes for each cohort of
the seven enclosures frc*u May to December, 196L, are presented in
Tables XXX through XXV.
Survival was good in all enclosures, except
II 2d, through August, but 8urvival rates declined from September
through November or December.
The means of the averages for the
total percent surviving voles captured in August through November or
December were calculated for each enclosure.
The means, in descending
TABLE XVIII.
SURVI'TAL RATES OF ADULTS, SUB-ADULTS, AND JUVENILES COMBINED FOR I Id, I 2d, AND II 3d
FROM JUNE THROUGH DECEMBER, 1963.
Month
No. %
I ld
June
July
August
September-I
September-Il
October
November
7100
July
No. %
343
8
24
34
49
69
66
100
100
100
100
100
100
6
13
23
25
47
67
71
100
100
100
100
100
100
100
6 100
8
27
100
100
100
100
8
August,i
Spt. I
No. %
No. %
229
0
6
2
0
25
10
142
75
Sept. 112 October
No.
Na.
November December4
No.
No. %
0
0
0
0
25
33
76
2
1
25
0
2
0
25
0
2
8
14
1
18
6
15
46
4
16
0
6
26
20
Lu
31
67
12d
June
July
Aueust
September-I
September-il
October
November
6
8
100
62
3
6
12
50
46
52
2
33
2
6
1+6
18
48
72
5
ii
17
U
33
33
38
48
68
70
2
14
8
15
28
46
33
31
35
60
60
69
1
36
62
81
48
35
100
4
15
50
56
3
15
27
100
100
100
August-Il for II 3d, 2
20
17
29
26
0
0
0
0
13
3
2
8
6
9
13
13
34
24
113d
June
July
August
September
October-I
October-11
November
2
3
0
0
0
6
6
0
October-I for II 3d,
38
52
75
2
25
2
13
48
56
68
10
17
37
60
20
42
25
37
47
60
714
October-lI for II 3d, 14
2
25
1
9
12
32
43
23
3,3
S
33
5
52
53
47
17
13
19
14
22
27
27
17
5
35
14
January for II 3d
TABLE XIX.
S1J±VIV1UJ RATES OF ADULTS, SUB-ADULTS, MID JUVENILES IN II id FROM HAT TO DECJ1BER, 1964.
July
Month Age
Adult
Sub-adult
Juvenile
Total
July
Adult
Sub-adult
Juvenile
Total
August
Adult
Sub-adult
Juvenile
Total
September
Adult
Sub-adult
Juvenile
Total
October
Adult
Sub-adult
Juvenile
Total
No.
%
No.
%
17
100
100
100
100
10
59
75
60
61
4
5
26
38
14
7
9
6
20
6
32
100
100
100
100.
141
17
10
0
27
100
100
0
100
0
16
100
100
100
100
100
100
0
100
9
32
3
3
Auguat
September
October
No.
No.
No.
2
2
5
12
So
0
19
14.
12
50
0
15
7
2
1
18
14
14
6
16
14
10
17
1
1
8
0
4
1
5
0
20
0
0
2
17
16
1
4
10
17
12
2
22
Iii
3
18
2
50
2
5
0
19
0
12
75
40
46
2
32
6
60
43
10
26
3
2
28
2
31
52
iS
21
28
25
7
3
2
C)
1
2
17
30
33
9
28
6
Decenfoer
No. %
0
2
17
53
1
0
19
0
46
0
16
8
3
0
11
7
13
22
44
0
39
47
30
0
41
Heari of average monthly survival - 30.5
0
TABLE XX.
SURVIVAL RATES OF ADULTS, SUB-ADULTS, AND JUVENILES IN II 2d FROM MAY TO
DECEMBER, 19614.
July
Month Age
No.
Adult
Sub-adult
Juveiile
Total
16
3
1
20
100
100
100
100
August
September
%
October
%
December
No.
%
No.
7
14J
5
0
31
0
0
1
100
30
0
0
0
0
0
0
0
0
0
0
0
0
0
0
26
70
15
140
10
27
6
2
2
1
33
20
58
0
13
0
30
0
13
0
9
1
214
140
0
0
12
21
10
17
0
1
0
100
8
140
6
No.
No.
0
No.
0
0
0
0
%
0
0
0
0
July
37
Sub-adult
Juvenile
Total
15
5
57
August
Adult
Sub-adult
Juvenile
7
27
22
Tota].
56
September
Adult
Sub-adult
Juvanile
Total
October
Adult
Sub-adult
Juvenile
Total
Mean of av
6
143
1
50
9
11
0
20
age
100
lOO
100
100
100
100
100
100
100
100
100
100
100
100
0
100
7ionthly survival - 31,3
17
7
2
28
2
28
1
114
iS
5
55
?3
10
5
37
23
3
2
11
9
22
39
27
14.8
6
ii
1
17
2
31
33
72
0
0
33
66
18
0
19
6
5
0
11
142
0
38
66
145
0
55
TABLE XXI.
SURVIVAL RATES OF ADULTS, SUB-ADULTS, AND JIWENILEFJ IN III 3d FROM MAY TO DECEMBER, i96I.
July
August
No.
%
September
No. %
October
No
%
December
No
%
Month Age
No.
%
No.
%
Adult
Sub-adult
Juvenile
Total
19
0
100
0
1
79
0
10
0
0
8
0
0
100
0
0
15
79
8
July
Adult
Sub-adult
Juvenile
Total
23
10
6
39
100
100
100
100
3
20
12
35
100
100
100
100
12
2!.
100
100
100
100
Subadult
16
12
100
100
Juvenile
Total
2
100
6
1
30
100
13
August
Adult
Sub-adult
Juvenile
Total
September
Adult
Sub-adult
Juvenile
Total
October
Adult
9
3
O
Mean average monthly survival - 39.3
12
8
2
22
!.2
0
0
Li.2
52
80
33
56
8
0
0
!i2
8
!.2
7
6
30
60
33
38
2
15
0
0
7
66
80
58
25
71
2
16
6
0
0
6
31
0
0
31
1
0
0
1
2
9
1
5
50
33
2
2
23
5
0
50
58
L8
0
2
9
0
10
7
17
3
25
!
!i.h
3
10
100
12
6
L
10
3
1
1
5
6
S
0
0
5
!
20
33
13
0
30
33
28
25
11
33
21
37
50
50
L3
TABLE XXII.
SUThIIVAL RATES OF ADULTS, SUB-ADULTS, AND JUVENILES IN III L. FROM MAY TO DEGERNBER, 19614.
August
July
Month Age
Adult
Sub-adult
Juvenile
Total
July
Adult
Sub-adult
Juvenile
Total
August
Adult
Sub-adult
Juvenile
Total
September
Jduit
Sub-adult
Juvenile
Total
October
Adult
Suii-adult
Juvenile
Total
Moan o
No.
15
1
0
16
30
8
7
145
33
21
16
70
16
142
17
75
10
30
0
140
%
No.
%
100
100
0
100
12
80
100
0
8
1
81
9
1
0
13
100
100
100
100
100
100
100
100
100
100
100
100
100
100
0
100
September
-__i4o.
0
17
14
14
25
October
No
%
November
No.
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
143
5
2
1
1
17
12
14
50
28
114.
0
0
13
0
0
19
142
7
15
14
9
10
14
12
2
6
114
14
19
25
3
10
30
38
62
2
28
14.0
12
17
7
12
10
1
6
20
53
100
0
56
3
1
0
14
100
0
25
57
50
57
55
13
14
8
14
8
50
12
28
3
23
18
31
14.
9
2
12
7
9
14
3.4.0
II
0
15
37
O
38
average moth1y survival - 30.0
0'
TABLE XXIII.
Month Age
Adult
su:b-adult
Juvenile
Total
July
Adult
Sub-adult
Juvenile
Total
August
Adult
Sub-adult
Juvenile
Total
September
Adult
Sub-adult
Juvenile
Total
SURVIVAL OF ADULTS, SUB-ADULTS, AND JUVENILES IN II Sd FROM XIC( TO DECEMBER, 19614.
No.
No.
114
1
3
18
30
7
5
142
214
39
36
99
114
148
i14
76
100
100
100
100
$
9
614
0
0
2
66
61
11
100
100
100
100
100
100
100
100
100
100
100
100
August
No. %
September
October
No.
No.
November
No. %
5
0
0
0
0
2
7
1
3
1)4
0
0
0
140
1
1
21
Li.
1
2
14
6
0
0
6
143
1
7
1
7
0
0
0
0
1
0
0
1
0
0
33
0
0
5
114
147
5
17
3
143
28
3
60
2
2
20
148
9
20
9
6
25
2
8
:L
22
56
17
L5
147
13
12
33
33
3
6
LiS
27
27
10
3
21
17
5
35
36
25
33
0
U
3
114
0
0
0
0
0
8
17
10
0
23
21
18
October
6
Sub-adult
Juvenile
Total
214
0
30
Mean oZ average monthly survival
0
17
29
0
8
27
1
7
100
100
0
100
214.5
TABLE XXIV.
SURVIVAL RATES OF ADULTS, SUB-ADULTS, AND JUVENILES IN III 6d FROM Mi1 TO DECEMBER, 1961..
July
Noth
Age
Adult
Sub-adult
Juvenile
Total
July
Adult
Sub-adult
Juvenile
Total
August
Adult
Sub-adult
Juvenile
Total
September
Adult
Sub-adult
Juvenile
Total
October
Adult
Sub-adult
Juvenile
Total
No.
%
10
l!
100
100
100
100
51
10
18
79
100
100
100
100
13
17
25
55
100
100
100
100
3
100
100
100
100
2
2
14.6
6
55
8
15
2
25
August
No.
%
No.
8
1
80
6
0
100
1
2
9
2
11
7
100
100
100
100
Mean of average monthly survival - 35.5
Septenther
No. %
November
No. %
60
50
100
1
1
0
10
1
0
0
0
0
10
0
0
0
0
10
0
0
61
2
1Li
1
7
1
7
13
1
6
1
2
25
10
11
2)4.
35
30
17
30
16
20
12
10
11
11
5
38
2
15
7
].
iS
60
27
Li.9
32
63
18
L.
Lt.O
6
33
53
3
3
14.2
October
%
No.
2
9
8
29
1h
1
5
9
33
15
27
0
30
66
33
29
11
18
1
0
0
0
22
138
114.
13
66
13
26
137
18
2
36
0
25
60
0
11
1414.
9
TABLE XXV.
URVIVlth BATE3 OF ADULTS, SUB-ADULTS, AND JUVENILES IN II 7 FROM MAX TO DECEMBER, i96t.
Month Age
No.
Adult
Sub-adult
Juvenile
Total
July
Adult
Sub-adult
Juvenile
Total
9
0
)4
13
52
32
7
91
August
Adult
Sub-adult
Juvenile
Total
35
33
19
September
Adult
Sub-adult
Juvenile
Total
56
October
Adult
Sub-adult
Juvenile
Total
87
9
0
65
I
8
0
12
%
100
0
100
100
July
August
No.
No.
8
89
3
0
0
100
92
0
!
12
100
100
100
100
100
100
100
100
100
100
0
100
100
100
0
100
Mean of average monthly survivaE - 31.5
2
5
31
16
b
51
September
%
No.
October
%
No.
0
0
0
0
1
1
25
8
16
9
2
30
36
28
28
33
30
25
28
28
12
3!i.
7
51
21
38
11
33
0
50
38
1
11
0
1
0
25
2
15
60
Sb
57
56
19
17
1
33
8
2
26
It
22
5
31
0
36
November
No.
0
0
0
0
%
0
0
0
0
12
23
5
16
0
17
0
19
11
15
20
33
21
25
1
55
55
0
55
15
0
18
33
27
0
28
1
5
0
6
62
0
50
14.
5
It
3
21
15
25
71
order, for III 3d, III 6d, II 7, II 2d, II id, III 1, and II Sd were
III 3d
39.3, 3.3, 31.5, 31.3, 30.5, 30.0, and 2b.5, respectively.
and III 6d had better survival throughout the study year.
Survival
for II 7, II 2d, II id, and III b was similar to one another, not as
good as III 3d and III 6d, but better than the low rate for II Sd.
III 1. had very good survival through August but showed poor rates
afterwards.
Juvenile survival was better in III 3d and III 6d.
In general,
survival of May and July juvenile cohorts rapidly declined in all
enclosures after August.
Adult survival rates dropped rapidly in
August and/or September but afterwards leveled to a more gradual
decline.
In swrmiary, II 1
rates for 1963.
and II 6d had the better over-all survival
In 19614, juvenile survival dropped in August, and
adult survival also declined sharply in August and September.
III 3d and III 6d showed better over-all survival than II 7, II 2d,
II id, and III 14, and
II 5d had the lowest survival rates following
August.
Dispersal Rinpe
The total mice caught, captures per ramp day, population
estimate, and percent soars and wounds of voles captured in the
dispersal ramps from July 2, 1963, to November 15, 1963, are given in
Table XXVI.
As the monthly population estimates increased, captures
72
TABLE XXVI.
TOTAL MICE CAUGHT, CAPTURES PER RAMP DAY, POPTPATION
ESTIMATE, MW PERCENT SCARS AND WOUNDS OF MICE
CAPTURED IN THE DISPERSAL RAMPS FROM JULY 2, 1963,
TO NOVBER 15, 1963.
Total
Caught
Ramp I 1
July
August
September
October
November
Total
Average
Ramp 1 2
July
August
September
October
November
Total
Average
3
6
12
15
20
Captures
Per &mp Day
.21
.29
.67
1.07
6.67
Population
Estimate
15
39
92
151
199
% Wounds
and Scars
0
17
25
20
25
56
.80
1
11
17
9
26
.07
.52
.50
21
36
93
1.86
156
7
2.33
230
0
9
22
19
L3
19
.77
Ramp 15
July
August
September
October
November
Total
verage
Ramp II 3
July
August
September
October
November
Total
Average
Ramp II 6
July
August
September
October
November
Total
Average
6
10
.21
.19
.33
.67
3
1.00
3
15
27
51
81
122
0
0
0
20
33
26
11
.37
5
11
13
.36
.52
.72
25
1.71
5.67
17
83
133
229
20J4
0
9
15
16
35
71
1.00
29
L.
.29
7
9
20
.3
37
91
13
25
71
1.11
.87
.33
1.00
12b
25
22
25
31
195
29
73
per ramp day generally increased.
Populations in their second year
o± high densities dispersed more than first year high density populations.
The average of 1.01 and 1.00 captures per ramp day for
Ramp II 3 and Raap II 6, respectively, were higher than the .80,
.77, and .37 averages, for Ramps I 1, I 2, and I 5, respectively.
Wounding percentages increased with the increasing amount of
dispersion.
The total mice caught, captures per ramp day, population
estimate, and percent scars and wounds of vales captured in the
dispersal ramps from June 2h, 196l, to December 9, 196li, are
presented in Table XXVII.
More mice with higher percentages of
wounds were captured in the ramps in 196!.
The dispersal movemen
was partially influenced by an earlier overutilization of grasses
in the summer causing cover to decrease through the fall.
Again,
dispersal movent was usually high when the monthly population
estimates were at high levels.
However, the captures per ramp day
were moderately high in November and December after populations had
declined, except in Ramp III 3, when wounding rates were generally
high.
Ramp III 6 had the lowest average captures 'per ramp day
(1.3) f or l96l.., but this average rate was higher than any ramp in
1963.
Ramps II 1, II 2, and II 5 had averages that were similar.
III 3d showed little dispersal movement until September when ramp
captures increased sharply.
Ramp III 3 had a 2.2 average for captures
per ramp day which was highest.
Ramp III 3 also had the highest
7L.
TABLE XXVII.
TOTAL MICE CAUGHT, CAPTURES PER RAMP DAY, 2(ULATI0N
ESTIMATE, AND PERCENT SCARS AND WOUNDS OF NICE
196.L,
CA1URED L THE DISPERSi RAMPS FROM JUNE
TO DECEMBER 9, 19&.
Total
Caught
Ramp II 1
June
July
August
September
October
November
December
Total
Average
Ramp II 2
June
July
August
3eptember
October
November
December
Total
Average
Ramp II 5
June
July
August
September
October
November
December
Total
Average
10
26
13
0
12
9
2
Captures
per Ramp Day
Population
Estimate
% Wounds
and Scars
2.5
307
136
1.9
208
0
103
82
20
23
38
0
33
86
100
1.7
1.0
1.0
61.+
72
1.8
33
30+
102
122
107
98
5
19
11
12
5
1.3
7
1.1.
-
.5
98
1
2.7
1.6
1.3
.7
60
26
36
50
80
29
100
60
1.5
1
20
20
9
3
3
5
61
.3
2.9
2.9
25+
82
222
.6
190
107
60
2.5
-
1.1
.li
1.5
100
25
35
67
33
33
20
36
75
TABLE XXVII CONTINUED.
Total
Caught
Captures
per Raino Day
?opulation
Estimate
% Wounds
and Scars
Nainp III 3
June
July
August
September
October
November
December
Total
Average
0
0
19+
.6
0
20
26
22
0
2.5
3.7
14.14
61
70
87
63
-
8
14.0
130
0
0
0
35
142
62
63
80
2.2
149
Ramp 1116
June
July
August
September
October
November
December
Total
Average
*
2
.5
16
2.6
1.3
9
5
14
.6
.6
8
1.6
14
2.0
18+
152
So
1149
1143
1414
95
58
-
22
140
50
75
50
i.3
- Indicates no trap period
142
76
average percent wounding (19) which occurred
during the period
September to December when population numbers were increasing and
vegetation was regressing. Ramps II 2 and III
percent average wounding. Ramps I I and I
5
6
both bad 1i2
had 33 and 36 percent
average wounding, respectively.
Pir8t year high density enclosures (Ramps I 1, I 2, and I
5)
had. lower average capture rates and wounding rates for dispersal
mice than the second year dispersal enclosures. Averages of'
captures and wounding for the l96L. second year high density Ramps
II 1, II 2, and II S were higher than in 1963 and were more
comparable to the 1963 second year high density Ramp II 6. The
third year high density populations (Ramps III
3
and III 6) presented
characteristics of' dispersion that deviated from other populations,
except possibly Ramp II 2 in 196k. In Ramp III 3, a high dispersal
rate (76 mice) nd a very high wounding rate
from September through December.
Ramp III
(b9
percent) occurred
6 had a high wounding
rate (b2 percent). More wounding occurred for dispersal mice from
the populations with third year high densities and from II 2d. This
suggests that more intraspecific strife occurred for dispersal mice
of the second and third year population phase.
In 1963, more males than females were captured in the ramps
except in Ramp II 3 where females comprised 51 percent o± the total
captured.
Dispersing males were mainly of adult and sub-adult age
groups with the adults being more numer'ous. Sub-adults were the
dominant age class fox' females.
77
The sante ramps in l96t produced similar sex and age dispersal
patterns.
II
Males were more numerous in Ramps XI 1, II 2, III 3, and
comprising SB, 57, 63 and 67 percent of mice captured, respec-
tively.
III 6.
Females comprised 63 percent of the total capture in Ramp
Adults were the numerous age class for males in Ramps II 1,
II 2, and III 6.
Sub-adults were the numerous age class for males in
Ramps Ifl 3 and II S.
Sub-adults were the dominant age class for
females in all l96L ramp captures.
In summary, captures per ramp day generally increased with
monthly population growth.
Wounding had a tendency to increase
as ramp captures increased even though the month to iso th
relationships were inconsistent.
Some dispersion occurred in
1963 even when little wounding was evident.
Mice of second and
third year high density populations had a greater tendency to disperse than mice of first year high density populations.
In general,
dispersal mice had a higher percentage of wounds when they were
from populations experiencing more years at high density levels.
More males than females were caught in dispersal ramps, except
Ramp XI 3 in 1963 and Ramp III 6 in 196b.
Adult arid sub-adult
males and sub-adult females were the numerous age classes in ramp
captures.
Wounding
The frequency of wounding occurring within a population is an
indication of the amount of intraspecific strife.
Examples of bead
78
and. rump wounds
encountered in this study are pictured in Figures
7 and 8.
The monthly percentages and mean annual percentages of scars
and woundà found on ail voles captured in the seven
from June, 1963,to January, 196)4.,
enclosures
The
are presented in Table XXVIII.
mean annual percentages of wounding for I id, I 2d, I Sd, and I 7
were similar to II 3d, II
(19 percent)
b,
and II 6d. II
than the other enclosures.
II
b
had more wounding
1 and 1 7 without dis-
persal ramps had higher over-all percent wounding (19 and 15,
respectively) than the enclosures with dispersal ramps.
Monthly p'oentages and mean annual percentages of scars and
wounds found on all voles captured from the seven enclosures and
the Caledania-6 plot from May through December, 1961L, are represented
in Table XXIX.
III 3d bad more wounding (20 percent) than
the other
enclosures. II 7 had a slightly higher wounding percentage (17)
than
II ld, II 2d, and II Sd. III I bad a lower wounding percentage (15)
than III 3d and IU 6th
The Caledonia-6 plot mice exhibited very
little wounding.
In suxmnary, for 1963 II Ii. bad higher percent wounding than the
other enclosures. Slightly more wounding occurred in II 1 and 1 7
than in the enclosures with dispersal
slightly more wounding than the
ramps.
In l96I,
other enclosures.
plot mice showed little wounding.
III 3d bad
Caledonia-6
Figure 7.
Head wounds of an adult vole.
Figure 8.
Rump wounds of an adult vole.
81
TAi3LE XXVIII. MOTHL
EiTAGE
P
O1 WOUJ
:i
AiD }OAN ANiUAL ?ENTAOE.3
FOUND 0 MICE APTUR1!D, AND
PXU1U FOft
OLOSURE I ThROUO} 7 ?R.0
;c.'J
THE TOTAL
JUNE, 1963, TO JANUARY, 19624.
Trep Period
Designation
I id
I 2d
I 5d
I 7
.
-
June
July
August
september-I
.eptemoer-II
October
Deoeiber
Januaxy
9
0
124
0
13
240
7
124
124
3
21
36
14
2
145
12
12
13
3
130
169
92
9
13
25
25
S
11
25
19
324
3
8
53
15
92
17 107
12 136
18 119
-'
ean Percent
Period
Desiguation
0
3
-
13
9
147
13
68
7
7
255
9
314,
914
8
No.
June
July
August-I
August-Il
September-I
eptember-II
Octocer-I
October-lI
November
December
3rrnazy
13
6
1
&sn Percent
8
5
9
No.
8
35
22
20
69
9
7
29
724
-
22
36
'LO
241
240
i24
153
202
173
35
12
20
19
57
9
-
80
117
71
11
205
59
10
12
-
11
30
3
-
116
-
10
10
No.
9
27
88
25
19
-
- Indicates no trsp period
13
j
15
Tix 3(
%
10
16
16
12
13
165
210
83
S
19
39
242
63
76
1314
2L8
146
TABLE XXIX.
MONTHLY PERCENTAGES AND MEAN ANNUAL PERCENTAGES
OF WOUNDS AND SCARS FOUND ON MICE CAPTURED, AND
THE TOTAL CAPTURE FOR ENCLOSURES 1 THROUGH 7 AND
CALEDONIA-6 PLOT FROM MI&Y TO DECEMBER, 196)4,
Trap Pe±'iod
II id
Designation
No.
May
July
August
September
12
October
November
December
25
Mean Percent
16
Trap Period
Designation
%
1)4
7
1)4
II Sd
No.
No.
)48
8
2)4
111
111
80
68
10
88
9
101.
5
20
-
8)4
1)4
65
70
27
II 2d
%
73
11
III 3d
Nay
July
August
September
0
13
6
III
1)47
11
121
90
13
)47
30
-
15
17
III 6d
)4
73
59
80
71
-
22
28
-
iS
16
9
7
Moan Percent
20
13
2)4
Indicates no trap period
29
*
17
106
123
103
35
-
9
6
iS
11
13
October
November
December
83
11
18
117
153
119
83
56
2)4
16
63
136
118
14)4
No.
69
No.
6
22
1
*
10
10
15
No.
19
59
65
71
25
21
26
11
II
Cal -6
No.
%
-
0
9
0
0
6
8
13
18
5
2
7
DISCUSSION
Agoniatio Behavior Versus Population Densities
The average fighting times are compared to the peak density
estimates for the seven enclosures during 1963 and 19614 in Table XXX.
It was generally evident that mice of first and second year phase
populations reaching higher estimated peak densities exhibited more
agonistic behavior.
Mice of the first year high density populations,
I 5d and I 7, displayed more over-all Lighting time, Tables II, III,
and IV, and higher estimated peak densities than mice of second
year high density populations,
II 14 mice exhibited the larger aiiount
of fighting behavior, Tables III and XXVIII, for second year high
density
populations. In 19614,
with one exception (III 3d), lower
average fighting times and lower peak densities were observed in
both the second and third year phase populations than were observed
in 1963.
II
Mice in the second year high
d, and II 7
density enclosures, II id,
generally reached higher peak densities and
exhibited slightly more fighting than those of the third year high
density enclosures, III 3d and III 6d.
These observed density and
fighting patterns correspond to Clarke's (19%) study showing that
more conflict existed in his higher populated group voles,
The
data suggest that a reduction in population densities and fighting
behavior may be related with the year phase of high density
populations.
Variations in behavior from the above statement did
TABLE XXX.
AVERAGE FIGHTING TINES AND PEAK DENBITY ESTIMATES FOR MICE GF ENCLOSURES 1 THROUGH 7
DURING 1963 AND 196t.
I
Enclosure
Year Phase
Fighting
Peak
Time in
Density
II Year Phase
Peak
Fighting
Time in
Seconds
Density
Seconds
1963
III Year Phase
Fighting
Time in
Pesk
Density
Seconds
1964
Id
10.3
199+25
9.5
208+39
2d
11.7
230+29
7.0
l22+21
5a
15.9
314.55L1.
12.6
222
7
33.5
LO9+8b
11.5
212L9
3d
9.2
229+29
11.0
130+26
b
13.7
269+13
9.L.
229+1.O
6d
1O.!.
29553
9.1
1S2+LO
1963
*
Two iandsrd errors
occur in 19614 for II 2d and III 3d. II 2d had the lowest density
and exhibited the least amount of fighting for the enclosures.
III 3d
displayed more wounding, Table XXIX, and a low density until December.
The factors that influence aggressive fighting characteristics
are not Ailly understood.
Even though less fighting occurred, the
third year high density enclosures, III 3d, III Li, and III 6d
displayed a slight increase in aggressive fighting, Tables II, III,
and IV.
I4ore mice eetablisbed the social characteristics at dominance
and aubordinance in these older populations which could have been
influenced by increased aggressive behavior.
Chitty (1960) proposed
that when populations of voles experience high densities, changes in
characteristics occur through selection.
Aggressive fighting behavior
may be one of these changes, but Clark (1962) states that the type of
fighting is learned, and that success in fighting re-enforces
aggressive activity.
Peak densities for first and third year phase dispersal enclosures
were lower than their respective year phase non-dispersal enclosures,
but this relationship did not entirely hold true for second
phase populations,
ar
Table XXX. II 14, I 7, and II 7 were generally
indicated to have more strife, wounding and fighting data of Tables
III, IV, XXVIII and XXIX, than the dispersal enclosures of their
respective year phase.
The data suggests that dispersal movement,
by temporarily lowering denaittes, may redee intraspecific strife
tn the first and, to a lesser extent, second year phase high densities.
The Caledonia-6 plot population is an example of a low density
population. These mice exhibited very little fighting behavior and
used threat tactics more
than
mice from higher densities, Tables IV
and XXIX.
Behavior Versus Sex and Age Composition
Higher peràentages of adults were found in I 2d, II
b,
and I 7
than in other 1963 enclosures * III 3d had the higher percent of
adults for the enclosures in 1961j. These above populations generally
showed high fighting averages, Tables III and IV, and wounding was
also higher for II ! and III 3d, Tables XXVIII and XXIX. Fighting
behavior is suggested to have been encouraged by the older age
structure in these
populations.
Clarke (195S)
found that adults
fight more than the young, and therefore aggressive behavior is
most likely to occur more among sexually mature voles.
In 1963, II
14
and I 7, non-dispersal enclosures previously
discussed, were the only enclosures that had more males than females
and displayed more fighting and slightly more wounding than their
respective year phase
dispersal enclosures.
one exception,
With
males were more abundant in ramp captures than females in 1963 *
In 19614, II 2d and III 6d were the
only enclosures with
more females
than males, and both, particularly II 2d, displayed less fighting
and wounding characteristics for the year. Bailey (19214)
that male voles inflict more wounds on other voles
states
than do females.
A higher ratio of males to females within these populations probably
influenced an increase of agonistic behavior to occur.
The low density Caledonia-6 population was characterized by
similar numbers of males and female8 and a high percentage of adults.
These mice displayed little strife, for they lacked the element of
high density.
Agonis tic Behavior Versus Reproduction
Clarke (l9) found that voles of higher density populations
had a shorter reproductIve season, and that an jncreaaed amount of
fighting behavior was suggested to have severe effects on reproduction.
This corresponds with the over-all findings for the
following populations of this study.
I Sd and I 7, with an in-
dication of more fighting, Table III, had lower reproductive rates,
Table XVI, than II L. and II 6d.
II b had higher wounding rates,
Table XXVIII, but did riot obtain as high a fighting time average as
did I Sd and I 7. The reproductive rates for the enclosures were lower in l96l than in 1963.
Second year pha8e enclosUres II Sd and II 7,
with slightly higher estimated peak densities and longer average
fighting time behavior, Table XXX, had slightly lower reproductive
rates than the third year
XVII.
ase enclosures III 3d and III 6d, Table
Although, III 3d mice showed higher wounding rates, Table
XXII, which indicates that strife was significant for thIs population
throughout the study year. The data suggest that increased strife
among mice of populations exhibiting higher average righting tl.mea
resulted in slightly lower reproductive perfonnanoe.
Louch (1956) found that reproduction did not change with an
increased population density, but tie did indicate that the litter
survival was adversiy eLfected at higher densities.
This study
indicates that agonistic behavior, a form of intraspecific strife,
at higher densities tends to alter reproduotion
Chitty (1952) infers that intraspecific strife may increase
prenatal mortality by affecting the physiology and behavior of
pregnant females.
Smith (196h) inferred that II 4 CE 4) exhibited
more prenatal mortality than I Sd (E 5), I 7 (E 7), and
II 6d
CE 6). Table XVI indicates that fewer lactating females than
pregnant females were caught in II 4 and, to a lesser extent, I Sd.
II 4 exhibited the highest fighting and wounding rates for second
year phase populations, Tables III, IV, XXVIII, and XXIX
From
this, it is suggested that prenatal mortality caused the II 4 peak
density to remain at a lower level than the peak density of II 6d,
Table XXX, which exhibited less fighting and wounding characteristics.
Prenatal mortality, an indication o.f disrupted social
structure which is correlated with intraspecific strife (Chitty,
1952; Clarke, 1955), has been suggested to have held down the peak
density of II 4.
Agonistic Behavior Versus General Survival
Clarke (19%) found that survival of infant and juvenile voles
was lees than adults.
This was evident in the study.
Juvenile
survival was best through August, 1963, and thereafter the sub-adults
Fran 196h, juvenile
and adults survived best as densities increased.
survival became poor in August as densities increased, and sub-adult
This adds
and adult survival declined in August and September.
further support to Smith1s (196L) 8uggestion that juvenile survival
decreases as densities Increase.
In 1963, II ii. and II 6d had better survival and showed less
fighting behavior, Table III, than I
d and I 7.
II 3d, with less
fighting, had better survival in the Nay, June, and January cohorts
than I 7.
This correlation indicates that survival may have been
adverely influenced by the higher fighting rates of I d and I 7.
In l96i, III 3d and III 6d had better survival than II 7,
II 2d, II ld, III !, or II 5d.
all.
II
d had the lowest survival of
Strife, indicated by fighting and wounding, was higher for
The
III 3d, II 5d, and II 7 than for III 6d, Table8 III and flIX.
better survival for III 3d was probably influenced by the better
cover condition in the fall.
The better survival of III 6d
was possibly influenced by less fighting behavior.
II 7 survival
was similar, in spite of the indication of more strife, to that
of II 2d, II ld, and III b.
Apparently, agonistic
behavior
had less of an influence on survival in 196h, With lower
densities, than was indicated for 1963.
Agonietic behavior is
suggested to be more of a stress factor limiting survival when
populations are at higher peak densities.
Agonistic Behavior Versus Dispersal Movement
In general, more males than females were caught in dispersal
ramps and this reduction in males tended to reduce the strife in
these enclosures.
Adult and sub-adult males and sub-adult females
were prodc*dnanty caught in the ramps.
of Smith (196b).
This follows the finding8
Dispersal movement increased as population den-
sities and conflict, indicated by wounding, increased among the
dispersal voles,
Tables XXVI and XXVII. In solitary behavior
observations it was found that dispersal mice displayed more
exploratory behavcx' and less active behavior than non-dispersal
mice, Tables VII and VIII.
This suggests that exploratory behavior
combined with conflIct promotes dispersion and movement.
Barnett
(1957) made similar deductions £ or Norway rats.
Mice of the second year high density populations indicated a
greater tendency to disperse than first year high density population mice, Tables XXVI and XXVII.
Dispersal movements, indicated
by captures per ramp day, increased in the second study year.
Second
and third year phase dispersal mice had a higher percent of wounding
per ramp capture than first year phase dispersal mice, which implied
that more fighting occurred before these mice dispersed.
This
91
suggests that dispersion characteristics may be linked with the
high density population year phase, and that more fighting occurs
among mice before they disperse from second and third year populations.
Also, dual trial observations indicated that fighting behavior
increased among dispersal mice as the study aogresaed into the
second year, Tables V and VI.
In 1963, male dispersal mice displayed
far less Lighting and more subnissive behavior than male nondispersal mice.
First year high density I ld, I 2d, and I
d, dis-
persal males varied in their fighting characteristics as compared
Dispersal males from III 3d and III 6d
to non-dispersal males.
consistently fought loss than non-dispersal males..
For l96b,
dispersal males displayed slightly less over-all fighting and
aggressive behaor than non-dispersal males.
from II ld, II 2d, and II
Dispersal males
d varied again in their fighting,
while both III 3d and III 6d dispersal males displayed slightly
lower fighting rates than non-dispersal males.
It is evident that
the dispersal male fighting rates for the earlier populations
increased to higher fighting rates in the older populations which
were more similar to non-dispersal male fighting behavior.
This
implies that conflict is a significant factor influencing mice to
disperse in older vole populations..
Where there was uq dispersal movement in second year populations, II b and II 7, exploratory behavior was less and fighting
92
occurred more, Tables III and IV.
Fighting was higher for I 7 mice.
This suggests that as densities increased, voles were forced
together and with no nsans to disperse fighting increased.
Scott
(1962) discussed bis cause of fighting in deer mice.
The evidence indicates that dispersion, influenced by fighting
behavior and exploratory behavior, is an important factor in temporarily alleviating hostility and reducing densities in a vole population.
Also, fighting appears to be a more influencial factor in
promoting dispersion of mice from a population characterized by
previous high den8ity years.
From the forgoing discussion, it is suggested that agonistic
behavior is a factor in regulating high densities of voles.
Increased
fighting tends to lower survival and, to a lesser extent, reproductive
rates.
In high density populations, vole numbers are suggested to be
temporarily reduced, in part, by increased dispersal movement which
apparently is connected with the high density year phase.
CONCLUSIONS
1.
Agonistic behavior
reach high densities.
is more apparent in vole populations that
Dispersal movement reduces intraapec±fic
strife by temporarily lowering densities of the fir8t and second
year high density phases. This was not so evident in the third
year high density populations. Voles of a low density population
fighting behavior.
utilize more threat behavior than contact
2.
Agonis tic behavior is more pronounced in high density pop-
ulations with a large number of adults.
At high densitios, a
larger ratio of males to females is suggested to increase
agoniatic behavior *
3.
increased
in lower
intraspecific
strife is suggested to have resulted
reproductive performance for populations exhibiting higher
average fighting times.
Prenatal
mortality)
induced by intra-
specific strife, has been suggested to have held down the peak
density level of a population ( II b) in this study.
14.
Agonistic
Juvenile survival decreases as densities increase,
behavior is suggested to be a stress factor limiting survival of
all age classes when populations reach the higher densities1
.
Exloratory behavior combined with fighting promotes dispersion
which increases with expanding population densities.
Dispersion
characteristics are suggested to be linked with the high density
9b
year phase
Non-dispersal males display more agonistic behavior
than do dispersal males a! the earlier year phases of high densities.
6.
This study indicates that agoniatic behavior, which in!luences
dispersal movement, survival, and, to a lesser extent, reproduction
is a factor in
th
regulation of high density vole populations.
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