The Auk 113(1):240-242, 1996
Age-biasedSpring Dispersal in Male Wild Turkeys
ALEXANDERV. BADYAEV?
3 WILLIAM J. ETGES,
1 AND THOMASE. MARTIN2
•Department
of Biological
Sciences,
University
ofArkansas,
Fayetteville,
Arkansas
72701,USA;and
2MontanaCooperative
WildlifeResearch
Unit, Universityof Montana,Missoula,
Montana59812,USA
In polygamousanimal species,the reproductive
componentof male fitnesslargely is determinedby
the number of femalesto which they can gain access
(e.g. Wright 1946).Accessto femalesoften is strongly
influencedby the possession
of high-qualitybreeding
or display groundsby males(Weatherheadand Rob-
female renestingand breedingreceptivenesscauses
changesin distribution of females.
Methods.--Ourstudywas conductedduring 19921993 in the Ozark
National
Forest in northern
Ar-
kansas.The study sitewas flat-toppedhills (elevation
to 746 m) with narrow valleys.Dominant canopyspe-
ertson 1977). For animals that move between winter
cies included white oak (Quercusalba), northern red
and breeding areas,accessto high-quality breeding
or displaygroundscan be determinedby timing and
distanceof suchmovements,but ability to hold highqualitysitescouldbe determinedby localfamiliarity,
aswell associaland physiologicalstatus(Greenwood
oak (Q. rubra),postoak (Q. stellata),shagbarkhickory
(Caryaovata),and shortleafpine (Pinusechinata).For
a detaileddescriptionof the studysite, seeBadyaev
(1995).All birdswere capturedusingcannonnetson
pre-baitedsitesdistributedthroughoutthe studyarea.
All capturedbirds were fitted with 120 g backpackstyle radio transmittersand releasedat capturesites.
Most of the 35 radio-taggedmaleswere locatedonce
every four to five days, although more frequent lo-
1980, Johnson 1986, Johnson and Gaines 1990, P•irt
1994, Tsuji et al. 1994).
Early dispersal and short-distance movements
should allow access to best sites and dominant
indi-
vidualsshouldbe expectedto exhibit suchmovement
behaviors. Moveover, shorter dispersal can enhance
the survival component of fitness becauseit often
reducespotentialcostsof increasedmortalityriskwith
dispersal distance (e.g. Johnsonand Gaines 1990).
Subordinates,however, may be expectedto disperse
longer distancesand move morewithin displayareas
becauseit takesthem longer and more movement to
cations and visual observations
also were
recorded.
Only birds with 15 or more recorded locationswere
usedto calculatehomeranges(for detailsof telemetry
protocol,see Badyaevet al. 1996).
Femalesinitiated80%of firstnestsby 1 May in both
years.Thus, the period prior to 2 May is referred as
"early" as opposedto "late," which extendsfrom 2
May to 2 June.Successive
locationsseparatedby more
find suitable areas from which a dominant individual
than 2 days but lessthan 10 days were statistically
will not exclude them. Here we examine this domiindependent (e.g. Swihart and Slade [1985] test for
nance hypothesis.
two-day intervals; t2/r2 > 1.85, P < 0.05) regardless
Wild Turkeys (Meleagrisgallopavo)are especially of time lags between them. Observationsseparated
suitable for study of potential effectsof dominance by five dayswere usedfor interlocationdistanceanalstatuson dispersaland movementpatterns.They are yses.The displayrangewasdefinedasthe homerange
polygynous and, in females, nest-site selection preoccupiedfrom 1 April through 15 June. This time
cedesmateselection(Healy 1992,Badyaev1994).The interval was basedon female nest-initiationphenolsocialstatusin thisspeciesis largelysetby age;young ogy (Badyaev1994).Dispersaldistancewas defined
malesare subordinateto older malesand can be pre- as the distancefrom harmonicmean of home range
vented from breeding by theseolder males(Healy usedin February to harmonic mean of display range.
1992).In addition,the useof radiotelemetryallowed Partial areawas calculatedassum of areasof all polyus to quantify female movementsduring springdis- gonsdrawn aroundcentersof activitydivided by the
persal and distribution of nesting areas(Badyaevet total area of single polygon of range occupiedby an
al. 1996).
animal (Kenward 1990). Home-range estimates,inWe predictedthat: (1) older malesshould disperse terlocation distances, and associated statistics were
the shortest distance; (2) movements of older males
computedusing RANGES IV software(Kenward 1990;
should concentratearound suitabledisplay grounds for details,seeBadyaevet al. 1996).Neither morpho(i.e. aroundlimited nestingareas;Badyaevet al. 1996) logical measurementsnor dispersalparametersdifonce they reach their display grounds, and should fered between study sitesor years (ANOVA, all P >
encompassa smaller area than subordinates;and (3)
0.3).We usedthe criteriaof Kelly (1975)and Steffen
if movementsof males in spring are influenced by et al. (1990) to classifymales into SY (secondyear
displayingactivity, malesare expectedto move more after hatching), TY (third year after hatching), and
and farther in later partsof the breedingseasonwhen
ATY (after third year sincehatching)age groups.
Results.--ATYmalesdispersedshorterdistancesthan
either SY or TY males (Kruskal-Wallis test, X 2 = 7.45,
3 Present address:Department of Biological Sciences, University of Montana, Missoula, Montana
59812, USA.
240
df = 2, P < 0.05; Table 1). Dispersal distancesof SY
and TY maleswere not significantlydifferent (X2 =
3.42, P = 0.12). Heavier SY males dispersedshorter
January
1996]
Short
Communications
andCommentaries
241
TABI.•1. Descriptive statistics(• + SE,with n and range in parentheses)of spring-dispersaland home-range
estimatesof male Wild Turkeys in the ArkansasOzarks, 1992-1993.
Age category
Parameter'
SY
TY
6.8 +
1.7 +
3.3 +
4.9 +
Spring dispersal(km)
5.1 + 1.0 (12, 1.1-12.6)
Harmonic-meanrange (km2) 18.9 + 7.9 (5, 2.5-36.7)
Multinuclear polygon (kin2) 6.9 + 1.6 (7, 2.1-12.7)
Convex polygon (kin2)
10.7 + 2.8 (7, 2.1-18.9)
ATY
1.4 (17, 0.5-22.2)
0.5 (9, 0.4-4.2)
0.9 (11, 0.9-10.8)
1.4 (11, 0.7-14.3)
2.6 + 0.7 (6, 0.4-4.7)
0.38 (1)
0.5 + 0.3 (3, 0.2-0.8)
0.9 + 0.05 (3, 0.92-1.0)
ßHarmonic-meanestimate,multinuclearpolygon by clustering,and convexpolygon methodsbasedon 90%-probabilitypolygons.
distances,and body massin springexplained59%of
the variation in spring dispersaldistancein this age
class(linear regression,F•,•2= 14.2,P < 0.005). Dispersaldistancesof TY and ATY malesdid not correlate
with body mass(both P > 0.2).
Display rangesof TY and ATY maleswere significantlysmallerthan thoseof SY males(Kruskal-Wallis
from being closerto suchareasby assuringfrequent
encounterswith females(seealsoBradburyand Gibson 1983, Schroederand White 1993). In the population under study, early nest initiation was the most
important factor contributing to nest survival (Badyaev 1994). Thus, males that reach spring display
groundsearliestprofit by mating with early-nesting
test, X • = 8.35, P = 0.01; Table 1). This difference was
females.
mostapparentwhen harmonic-meanestimatesof disAdult malesoccupiedsmallerdisplayhome ranges
than did SY males (see also Hoffman 1991). Adultplay range were used (P < 0.001; Table 1). Males of
different agesuseddisplayrangesdifferently (Fig. 1). malehome-rangeusewasmoreheterogeneous,
which
Partial-area estimate differed between age classes possiblyreflectsan uneven distribution of suitable
(Kruskal-Wallistest,X• = 3.61,P = 0.06)and averaged nestingareasof females(Badyaev1994,1995,Badyaev
0.49 + SE of 0.13 (n = 10, range 0.11-1.0) for adults et al. 1996). Adult-male movements within their dis(TY and ATY males combined) and 0.79 + 0.13 (n =
play ranges were more restricted than those of SY
7, range 0.37-1.00) for SY males. Adult-male use of
males, potentially becausenondisplaying SY males
range was concentratedaround several centersof acexperiencereducedaggressionfrom older conspeciftivity (• = 1.8 + 0.2), but SY male range usewas less icswhen moving amongdisplaygrounds(e.g. Healy
1992). Adult males showed considerable fidelity to
restrictedto particularareas.Rangeestimatesfor subadultsincreasedwith almost every additional ob- display siteswithin the breeding season(Fig. 1). Berservationbecausebirdsfrequently ventured into pregerud (1988) and Phillips (1990) also speculatedthat
viously unvisited areas(Fig. 1).
female forest grousespreferred males showing the
For SY males, distances between successive loca-
tions averaged 4.1 + 0.3 km late in the seasonand
were significantlylonger than 2.2 + 0.1 km distances
early in the season(pairwise t-test, t = 3.89, P = 0.02).
However, there were no differencesbetween early
(4.6 + 1.3 km•) and late (9.0 + 3.5 km•) home ranges
in this age class(t = 0.67, P = 0.53). For adult males,
distancesbetween successivelocationsaveraged 1.4
+ 0.4 km late in the seasonand 1.3 + 0.2 km early
in the season,and were not significantlydifferent (t
= 0.26, P = 0.79). Adult male home rangesused late
in the season(2.4 + 1.3km•) were significantlylarger
than home rangesusedearly in the season(0.6 + 0.1
•
'•
100-
• ----
-•- SY
75-
u_ 50z
•
25-
km•; t = 3.56, P = 0.01).
Discussion.--Our
findingswere consistentwith predictions of the dominance hypothesis:late-winter
home rangesof ATY maleswere closerto spring display groundsthan were rangesof youngermales.In
addition, larger SY males, which presumablyare
dominantover smallerSY males,alsodispersedshorter distanceswithin this age group. Becausesuitable
habitatsfor nestingare limited in our study areaand
prenestingdispersalof femalesis influencedby nesthabitat searching(Badyaev1994,1995),malesbenefit
0
•
15
25
•5
45
PERGENT
55
OF
65
75
85
95
OBSERVATIONS
Fig. 1. Patternsof displayrange use in SY (n = 6)
and adult (TY and older; n = 8) male Wild T•tkeys.
SE showRfor eve• [20 + 10•] petceRtageof obser-
vation for SY males,and for eve• [25 + 10•] percentageof obse•ation for adult males.
242
ShortCommunications
andCommentaries
most predictability in display behavior when near
nestinggrounds.Male fidelity to displayingsitescontributesto maintaining safedistancesbetweenfemale
nestsand male display sites,ensuringthat maleswill
not follow females to their nesting areas, thereby
making them more conspicuousto predators(Bergerud 1988).
Wild Turkey malesof all examinedage groupsincreased their movements
later in the season. The ob-
served pattern is consistentwith our prediction and
could result from a decline in availability of receptive
females and changesin the previously established
hierarchy in breeding areasas a result of human dis-
turbance(e.g. hunting). In addition, more areasbecamesuitablefor nestinglater in the season(Badyaev
1995) and, therefore, female distribution was not so
restrictedas it was early in the season.
Acknowledgments.--We
are grateful to D. Frick, D.
Hasenbeck,A. Hodgson,T. Lane, and K. Teter for
help with the fieldwork. We thank F. C. Jamesand J.
E. Johnson for helpful discussion.This paper was
significantlyimproved by commentsfrom A. T. Bergerud, G. D. Schnell, M. A. Schroeder,and an anonymousreviewer. The supportof the ArkansasGame
and Fish Commissionand the University of Arkansas
is gratefully acknowledged.
[Auk,Vol. 113
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