Distribution, temperature and population studies of Sceloporus graciosus graciosus in Yellowstone
National Park
by George Allen Algard
A thesis submitted to the Graduate Faculty in partial fulfillment of the requirements for the degree of
MASTER OF SCIENCE in Zoology
Montana State University
© Copyright by George Allen Algard (1968)
Abstract:
A study was conducted during the summers and the winter of 1964 and 1965 to determine the
distribution of Sceloporus graciosus graciosus in Yellowstone Rational Park and to determine
temperatures and selected population characteristics of the lizards in three study areas in the Rorris
Geyser Basin. The main lizard populations were found in the Rorris, Shoshone and Heart Lake Geyser
Basins. Small populations and scattered individuals were found in Black Sand Basin, a thermal area
along the road to Mary Lake, a small thermal area near Mary Lake and the Artist Paint Pot area. Only
one lizard population was found in a non-thermal area, that being within the town of Gardiner,
Montana. No lizards were found at Mammoth, although they had previously been reported there. The
largest male and female measured (snout-vent length) were 54 and 58 mm respectively, while the
young-of-the-year averaged about 26 mm. Three age classes were recognized on the basis of snout-vent
length; young-of-the-year, juveniles and adults, Data indicate that the lizards in the Rorris Geyser
Basin exhibit growth at least through their third summer of life. The mean cloacal temperature for 32
field measurements made with a Schultheis rapid reading thermometer was 29.8 C. Both the mean air
temperature one foot above the ground (22.3 C) and the mean substrate temperature (24.5 C). taken at
site of capture, were significantly lower than the mean cloacal temperature. Six thermocouples were
used to record temperatures in six selected sites in the Rorris Basin. A mean afternoon temperature of
31.8 C was recorded by a thermocouple on a basking rock in the Rorris Geyser Basin, which closely
approximates the mean cloacal temperatures of the lizards. Population estimates were made by the use
of marked lizards in the three study areas at Rorris. The highest estimate obtained was 120 lizards in
Area 1. In 1964 the young-of-the-year were first seen on August 15th and in 1965 they were first seen
on August 12th. DISTRIBUTION, TEMPERATURE AND POPULATION STUDIES OF SCELOPORUS
GRACIOSUS GRACIOSUS IN YELLOWSTONE NATIONAL PARK
by
GEORGE ALLEN ALGARD
*
A thesis submitted to the Graduate Faculty in partial
fulfillment of the requirements for the degree
of
MASTER OF SCIENCE
in
Zoology
Approved:
Head, Major Department
Chairman, Examining Committee
MONTANA STATE UNIVERSITY
Bozeman, Montana
March, 1968
iii
ACKNOWLEDGMENTS
To the following, the author wishes to extend sincere appreciation
for their contributions to this study:
Dr. Robert E. Moore, Montana
State University, for field assistance and guidance in the preparation
of the manuscriptj Mr. John Good and Mr. Bryan Harry,' National Park
Service, for cooperation and specimen collection privileges granted in
Yellowstone National Park; Mr. Charles Mueller and Mr. Britt Lewis, for
field assistance and encouragement; Zoology and Entomology Department,
Montana State University, for supplies and use of equipment.
During the
study, the author was employed by the National Park Service as a naturalist.
iv
TABLE OF CONTENTS
Page
VITA e
e e 9 o o » » » o e " e * e e # » o e o e a » » o » e e e e » e e o » » e » * e » # e * e o # ® e » e » 0 e * e » e * o o »
11
ACKNOWLEDGMENTS o*********************************************!*,***
iii
LIST O^* TABLES,a*,*,®®®,,*®®**,*,®*®,,,,,®®,,**®®*,*®*,#,,*®#,,,,®
v
LIST OF FIGDk ES®®*»®®®®®®®®®®®#a®®®®®®®®®®®®®®®®***®®*®®*®®,> 0 0 0 0 4 0 «
vi
.00OOOOOOOOO0OOOO000OO00O9O40OO000040O90OO00OO9O00OOO0OOOOO
vii
INTRODUCTION®®***®***®®®®*®®*®®®®®®®®®®®*®®o**®®®®#®®®®**®*®*®®*®®
I
METHODS o ®
3
ABSTRACT.
® e 9 e e ® o e 9 ’ 9 » e ® e ® o e ® ® ® » e ® e ® 9 9 e ® e e o e e ® e ® 6 e ® e e ® e ® 9 » ® e 9 e ® e e ® ® e
DISTRIBUTION OF THE SAGEBRUSH LIZARD IN YELLOWSTONE PARK..-..®.®®.®
NORRIS GEYSER BASIN POPULATIONS. a
No3ms
" V G T lt
T 0 l i ij j s 2 rS /tu n rs
® ® ® ® ® . ® * ® ® ® * ® . * ® * * ® ® * ® ® * ® ® ® ® ® . ® ® ®
. o ® ® ® ® * ® ® ® ® ® ® ® ® ® ® * * ® ® ® ® ® ® ® ® # ® ® * ® ® ® ® * ® ® ® ® * ® *
I
e o e e e o e e e ® e 6 e o e ' e e » ® e e ® 9 6 ® » e e ® » » e e e e o o » e e
s " b u d ,i6 S
P optilOi-!.3.on s"kud.!©s®
S fH d .
O i C t i v
i
t
y
o' e o
® ® * ® ® ® ® ® ® * ® ® ® ® ® ® * ® ® ® # o * ® * ® ® ® ®
® * ® * ® * ® ® ® # * ® ® ® ® o ® ® ® * ® * ® ® * ® ® ® ® ® * ® ® ® ® ® * ® ® ® ® ®
5
12
12
15
15
23
DISCUSSION0®®®®®®®®®®»®®®®®®®®®®®®®®®®®®®®®»»®®®®®®®®®»®®®®®®®®®®®
27
LITERATURE CITED® ® ® ® o ® ® ® ® ® o ® ® o ® ® ® ® ® ® ® * ® ® o ® ® ® o * ® ® ® ® ® ® ® ® ® o ® * * ® ® ® * ® ® ®
33
V
LIST OF TABLES
Table
Page
I. Average snout-vent lengths and ranges (in mm) for
Sceloporus graciosus by months................ .........
16
II. Distribution of 32 Sceloporus eloacal temperatures (C)......
18
III. Selected environmental temperatures (C) in the Eorris Geyser
Basxn durxng July of 19^5....................................
21
IV. Population estimates by area for 1964 apd 1965.....
25.
V. Total number of lizards marked by area in 1964 and 1965.....
26
i
vi
LIST OF FIGURES
Figure
I0
2.
3*
5.
Page
Map of the distribution of Seeloporus graciosus in
Yellowstone Farko 000000*00000000000000000000000 ***** ***
Photographs showing a typical rhyolite-covered hillside
(top) and dense common juniper cover (bottom) at the base
of the hillside in areas of lizard habitation*. o * o * * o o * * * *
8
* *
9
Map of Horris Geyser Basin study areas.*.
13
Cloacal temperatures of 32 lizards at time of capture versus
air temperatures (I ft. above surface) at site where.lizards
were initially seen *o***.*.****************************.**.*
19
Cloacal temperatures of 32 lizards at time of capture
versus temperatures of the substrate where lizards were
initially seen*. . . . o . . . . . . . . . * . . . . . . . * * * * * * * * * * * * * * * * * * *
20
* * * *
■ vii
ABSTRACT
A study was conducted during the summers and the winter of
and
1965 to determine the distribution of Sceloporus graciosus graciosus in
Yellowstone Rational Park and to determine temperatures and selected
population characteristics of the lizards- in.three study areas in the Rorris
Geyser Basin, The main lizard populations were found in the Rofris,
Shoshone and Heart Lake Geyser Basins* Small populations and sdattered
individuals were found in Black Sand Basin, a thermal area along.the road
to Mary Lake, a small thermal area hear Mary Lake and the Artist Paint.Pot
area* Only one lizard population was found in a non-thermal. area, that
being within the town of Gardiner, Montana. Ro lizards were found.at
Mammoth, although they had previously been reported there. The largest
male and female measured (snout-vent length) were
and 98 mm respectively,
while the young-of-the-year averaged about 26 mm. Three age classes were
recognized on the basis of snout-vent length;.young-of-the-year, juveniles
and adults, Data indicate that the lizards in the Rorris Geyser Basin
exhibit growth at least through their third summer of life. The mean:cloacal temperature for 32 field measurements made.with a Schultheis rapid
reading thermometer was 29.8 C. Both the mean air temperature one. foot,
above the ground (22.3 C) and the mean substrate temperature (24,5 C ).taken
at site of capture, were significantly lower than the mean cloacal tempera­
ture 0 Six thermocouples were used to record temperatures in six selected
sites in the Rorris Basin. A mean afternoon temperature of '31.8 C was
recorded by a thermocouple on a basking rock in the Rorris Geyser Basin,
which closely approximates the mean cloacal temperatures ,of the lizards.
Population estimates were made by the use of marked, lizards in the "three
study areas at Rorris. The highest estimate obtained-was120 lizards in
Area I. In 1964 the young-of^the-year were first seen on August 15th and
in 1965 they were first seen on August 12th.
INTRODUCTION
The distribution of the sagebrush ligard (Sceloporus graeiosus
graeiosus Baird and Girard) includes parts of 11 states primarily in the
Great Basin area of the United States (Stebbins, 19^4)„
Within these states
sagebrush lizards may be found in elevations varying from 4 <,500 to 10,000
feet where they commonly inhabit p!non-juniper zones, sagebrush zones and
even sparse coniferous forests which allow sufficient light penetration.
They are found in and around rocks, piles of brush, logs and debris, and
low-growing shrubs in these areas.
The earliest reference to the sagebrush lizard in Yellowstone National
Park was made by Yarrow (1883)#
Since that time there have been numerous
reports of lizard sightings made by park rangers and recorded in museum
records, which are located in the Yellowstone National Park Library in
Mammoth,
Sightings have been recorded for Old Faithful in 1926, Black
Sand Basin in 1929, Mammoth in 1930, and Norris in 19513 1954, 1964 and
1965»
Several sources describe the lizard and some of its activities
(Yeager, 1926, 1929; Beal, 1951J Turner, 1955)°
These references, when
viewed in perspective, indicate several important things: all the lizard
sightings were made in or near areas of thermal activity, the lizard
populations seem to be discontinuous, and the lizards are no longer found
in some of the areas in which they were originally reported.
The objectives of the present study were to first, determine the
distribution of the sagebrush lizard in Yellowstone National Park, second,
determine the size and relative isolation of adjacent but partially
isolated lizard populations in the Norris Geyser Basin, and third, record
-2-
snout-vent lengths and environmental and cloacal temperatures of the lizards„
The study w a s .conducted during the summers of 1964 and 1965, and some field
observations were conducted in the winter of 1964-65 in Yellowstone
national Park, Wyoming*
METHODS
During Doth summers of the study visits were conducted to areas where
Sceloporus had been reported and to areas in which their presence was
probable.
Due to the limited amount of time and the inaccessibility of
some of the areas, some lizard populations may have been missed, but all
the most likely areas, both thermal and non-thermal, were checked.
Warm, sunny days were chosen whenever possible in checking the areas
for the presence of lizards.
The possibility of over-looking lizards which
may have been under cover due to cool temperatures was diminished in this
way.
A population study was conducted in three adjacent but partially
isolated areas in the Norris Geyser Basin both summers, with most of the
study time being alloted to this area.
the vegetation in the areas was made.
Only a qualitative assessment of
All plant names were taken from
Booth (1950) and from Booth and Wright (1966).
All statistical analyses
used in the paper were taken from Li (1964).
It was early found that the most practical way of capturing the lizards
in the Norris area was by hand.
Because of the terrain and the speed and
agility of the lizards, especially on warm days, two people could accomplish
the task much more efficiently than could one.
When the lizards were cap­
tured, their cloacal temperatures were immediately taken with a Schultheis
rapid-reading cloacal thermometer.
The air temperature was taken at the
same time about one foot above the ground with the thermometer shaded, and
the temperature of the ground or rock on which the lizard had initially
been seen was also taken.
Snouth-vent lengths were taken at this time, and
-4-
the lizard was classified as an adult male or female, juvenile male or
female (about one year old), or as a young-of-tlie-year (not seen until
about the middle of August)e
The lizards were marked oh the dorsal side
with a dab of brightly colored Testers model paint so they could be
easily spotted in subsequent population estimate counts»
Estimates of
population sizes were determined by use of the Lincoln Index method,
(Dasmann and Taber, 1955)»
Different colors of paint were used in the
three areas so that if any migration occurred between the populations
it could readily be determined.
The first marking period each year was
in June, followed by several subsequent periods in July and August.
different color of paint was used for each marking period.
A
In this way
the marking periods could be separated, and. also it could be estimated
about how long the paint remained on the lizards.
In one of the areas a recording potentiometer was used during the
second summer of the study to record selected environmental temperatures.
A small a-c generator provided power for the operation of the potentiometer.
Six leads of l6 gauge, iron-constantan thermocouple wire were run from
the potentiometer to six sites selected for temperature measurement.
To
insure that the ends of the thermocouple wires would not become corroded
and give false readings they were' coated with epoxy resin.
The thermo­
couple sensing elements were 3™^ mm in diameter and were an opaque white
in color due to the epoxy resin coating.
The distribution of the leads
and the temperatures recorded were as follows:
-5-
Siliceous sinter area
Thermocouple I - ground temperature
Common juniper (Juniperus communis) and lodgepole pine (Pinus
contorts) basin area■
Thermocouple 2 - air temperature
Thermocouple 3 - ground temperature
Easterly exposed rhyolite hillside
Thermocouple 4 - air temperature
Thermocouple 5 - rock surface temperature
Thermocouple 6 - ground,temperature under a rock
Thermocouple I was covered with several mm of siliceous sinter so that
it would not be in the direct rays of the sun.
Thermocouples 2, 3, ^ and
6 were shaded so that temperatures recorded would not be in direct sun­
light.
Thermocouple 5 was placed on a rock in direct sunlight, because
lizards were often observed sunning themselves on this rock.
All air
temperatures taken were recorded at approximately one foot above the
ground,
Ho really satisfactory method was developed for obtaining rock
surface temperatures.
Geiger (1957) showed that surface temperatures
taken with a mercury thermometer are not completely accurate.
Hot
enough of the thermocouple sensing element could be placed in contact
with the rock surface, and probably all readings were somewhat low.
However, all rock temperatures were taken in the same manner, so at least
the error should be realtively the same.
The potentiometer was used daily
whenever possible and temperatures were recorded for a 15-minute period
-6-
for each of the six locations»
In conjunction with this a maximum-
minimum thermometer was used to record daily air temperature extremes in
the area .
DISTRIBUTION OF THE SAGEBRUSH LIZARD IK YELLOWSTONE PARK
The distribution of the sagebrush lizard in Yellowstone National Park
is seemingly limited to areas of thermal activity (Figure l),
The fact
that an area has thermal features does not mean that it supports lizards,
however.
Those areas which do not have sufficient cover in the form of
trees, shrubs, logs and rocks apparently do not have lizard populations
present.
The Norris Geyser Basin (elevation 7*524 feet), Shoshone Geyser
Basin (7,800 feet), and Heart Lake Geyser Basin (7,600 feet) appear to
support the largest lizard populations, and all these areas are similar in
appearance.
All have rhyolite boulder-covered hillsides on which common
juniper and stands of lodgepole pine trees are present in varying amounts
(Figure 2),
Black Sand Basin, a thermal area along the road to Mary Lake, '
a small thermal area near Mary Lake, and the Artist Paint Pot areas support
some lizards, but they do not appear to be as abundant there as in the
aforementioned areas.
The Artist Paint Pot area supported some lizards
in 1964, but none were found there in 1965.
It was felt that the area
was, in general, wetter in 1965 than it had been in 1964 due to the
presence of several new cold water springs.
As a result of these springs
the ground was damp, and the area in which the lizards had been found in
1964 had been changed from a dry area to one which was wet and supported
a heavy growth of mat-like mosses.
The population in the Black Sand
Basin had apparently decreased since they were initially reported in the
area in 1929.
The largest number of lizards the author ever saw in a
■8
M A M M O T H H OT SPR IN GS
TOWERJCT>
LEGEND
M AIN
A
A UT O ROADS
R OAR IN G MTN.
TRAILS
M O N U M E N T GEYSER B A S I N
A
,NORRIS
T H E R MA L AREAS - N O L I Z A R D S
N O N THERMAL AREAS W I T H LI ZARDS
T IS T P A I NT
* POTS
X/
T HER MAL A REAS W I T H LI ZAR DS
O N JCT.
NORRIS GEYSER B A S I N A
N O N • THERMAL AREAS - N O LIZARDS
0 1 2 3 4 5
ISON JCT.
M AR Y LAKE A , ' ' '
FIS H IN G
LOWER GEYSER BA!
BRIDGE
M I D W A Y GEYSER BA!
BLACK S A N D B A S I N
UPPER GEYSER
k A BA SIN
D F AI THFUL
'YELLOWSTONE
LAKE
' X A HEAHT LAKE
X G E V S E l B ASI N
Figure I.
Map of the distribution of Sceloporus graciosus in Yellowstone
Park.
-9-
Figure 2.
Photographs showing a typical rhyolite-covered hillside (top)
and dense common juniper cover (bottom) at the base of the
hillside in areas of lizard habitation.
—1 0 —
one-day observation of the area was twOj, which^ judging from the numbers
seen in any one day in other areas (as many as 20)} was certainly not
indicative of a large population..
According to reports in the museum records at Mammoth, lizards
had been seen in the Mammoth Hot Springs and Old Faithful areas.
At the
time this study was conducted no lizards were seen in either of the areas.
However, the sighting in the Old Faithful area (Yeager, 1926) was
probably near or in the Black Sand Basin,
following thermal areas:
Lizards were not found in the
Roaring Mountain, Monument Geyser Basin, Lower
Geyser Basin, Midway Geyser Basin and West Thumb Geyser Basin.
These
areas all seemed to be lacking in cover. -In none of these areas was
there an abundance of the rhyolite boulders with which the lizards were
associated in the Horris, Shoshone and Heart Lake Geyser Basins.
Also,
the small numbers of common juniper plants and lodgepole pine trees may
have been a reason for the absence of lizard activity.
Areas exhibiting many of the characteristics of the thermal
areas in which lizards were found but lacking thermal activity were also
checked.
The only non-thermal area in which lizards were found is within
the town of Gardiner, Montana, which Is located just outside of the north
entrance of Yellowstone Park*
The lizards were seen on the boulder-strewn
west side of the Yellowstone River.
There is spotty thermal activity in
this area, but whether it is sufficient to result in a general warming of
the ground is unknown.
Several areas were checked both upstream and down­
stream from Gardiner, but no lizards were found.
Other non-thermal
-11-
rhyolite hillsides common throughout the Park were checked also, but
failed to yield any evidence of the presence of lizards.
EORRIS GEYSER BASIE P0PULATI0ES
Eorris study area
The Eorris area experienced volcanic activity in the Pliocene epoch
. which resulted in the deposition of Yellowstone or welded rhyolite tuff.
Alluvial and hot springs deposits which started in the Quaternary period
resulted in siliceous sinter deposits on the rhyolite plateau (Boyd, 1961).
This hot spring activity along with normal erosion has caused basins or
pockets to be formed in the original rhyolite flow.
The Eorris Geyser
Basin is one such pocket, and it is the lowest spot in the Eorris area,
surrounded on all sides by timbered rhyolite slopes.
On the west edge of the Eorris Basin there is a series of low
rhyolite hills in which there is thermal activity.
The rhyolite on these
hillsides is in various stages of decomposition, consequently there are
many cracks and crevices present.
These openings provide protection and
shelter for lizards, and the populations of Sceloporus in the Eorris
Geyser Basin, as well as in other areas within Yellowstone Park, appear
to be limited to this type of habitat.
The study area at the Eorris Geyser Basin consists of three adjacent
but partially isolated segments (Figure 3 )»
west of the museum about § and
referred to as the Ragged Hills.
Areas I and 2 are located
miles, respectively, and are in what is
Area I is an east-facing slope, while
Area 2 has north, south and west-facing slopes.
the slopes are dissected by small gullies.
In both of these areas
Area 3 is located approximately
mile north of the museum, just west of Sieve Lake*
In the center of
this area is a rhyolite outcropping or knoll on which lodgepole pine and
-13-
area
3
POR C ELA IN
B A S IN
IAREA
LEGEND
M A IN
AUTO
ROAD
S T UD Y A R E A S
MUSEUM
LO CATIO N
FIRECRACKER
SPRINGS
PO TENTIO METER
1200
FEET
BACK
F igure 3
OF
JVfe-P o f Norris Geyser B a s i n s t u d y areas
-14-
cozranon juniper are present.
Surrounding this is an open area
scattered rocks and sparse vegetation.
with only
Area 3 is the smallest of the
three areas. ■ Lizards were found in small numbers in other areas within
the Norris Geyser Basin, but the three areas chosen seemed to be main
population centers and this was the reason for their selection.
Tantalus Creek, which is mainly run-off from thermal features,
separates the three areas.
There are many small pockets of thermal
activity along Tantalus Creek as well as several geysers which dump
boiling water into the Creek at varying intervals along its length.
The vegetation -in the area is confined mainly to the rhyolite hill­
sides.
Lodgepole pine is the dominant tree form, interspersed with an
occasional limber pine (Pinus flexilis).
Both trees have shallow, spreading
roots and hence are well-adapted to the shallow, rocky soil present at
Norris.
Common juniper grows along the hillsides and in the alluvial
deposits at the bases of the slopes.
The only other plant in any
abundance on the rhyolite hillsides is kinnikinick (Aretostaphylos uvaursi).
The thermal activity in the basin-areas between the ridges leaves
deposits of siliceous sinter on the ground surface.
This material is
impervious and forms a coat or shell over the ground, and vegetation in
the vicinity is scarce.
On the edges of the basins where some alluvium
remains, pussypaws (Sprague umbellate) are found growing.
-15-
Snout-vent lengths
Snout-vent lengths were obtained on 117 lizards.
The data were broken
down into three age groups by months on the basis of size (Table l).
Snout-vent lengths of the various year classes indicate that growth
probably ceases between September and May each year,
A discrepancy
appears between the largest juvenile captured in August (k2 mm) and the
smallest adult captured in June (k7 mm), but this was probably due to growth
after capture in September and before capture in June.
It is highly
probable also, that the lizards captured in the spring were not the same
ones that were captured in the fall.
Data indicate that the lizards exhibit growth at least through their
third summer of life.
The largest male and female measured were $4 mm and
58 mm respectively, while the young-of-the-year averaged about 26 mm.
The
snout-vent lengths of adult females and males were tested with a Student’s
t-test at the 5% level of significance and although females appear to be
slightly larger than males, the difference is not significant.
Temperature studies and activity
The active season for lizards in Yellowstone Park varies somewhat from
year to year, but five months is probably the maximum.
Snow and cold
weather is not uncommon in May, and winter weather can set in any time
after August.
The study began in June, 196k, hence the date lizards first
appeared in the spring of that year was not determined.
In 1965, although
periodic trips were made to Horris in the winter and spring, no lizards
were seen until June 5«
In 1966, however, they were seen on May 2
T A B L E 1«,
A v e r a g e snout - v e n t lengths a n d ranges
YOUEG-OF-THE-YEAB
(in mm) f or Sceloporus graeiosus b y m o n t h s .
JUVENILES
ADULTS
Males
Females
Mean
Range
N
'Mean
Range
N
Mean
Range
N
June
29.1
24-34
14
48.3
47-51
6
51.8
48-58
10
July
34.1
30-37
9
48.9
47-51
7
49.7
45-52
9
36.3
32-42 .18
49.9
48-54 10
51.0
49-54
13
Month
Mean
Range
N
Aug.
26.6
26-29
11
Sept.
26.4
24-30
10
N a sample size
None measured
None measured
None measured
”17”
(.Mueller, 1967)»
The difference in dates on which the lizards were first
seen in 1965 and 1966 can probably best be explained by differences in
spring temperature records from West Yellowstone, Montana.
In 1966 the
average air temperature for the month of Ifey was 4-7»0 3? (8.3 C), and
there were 2k days during the month when the temperature dropped to 32 F
or below.
Whereas in May of 1965, the monthly average was 4-0.5 F (4-.7 C),
and there were 29 days during the month when the temperature descended to
32 F or below,
(U, S, Weather Bureau, May, 1965, 1966)„
During the two
years of the study the latest date lizards were found was September 17,
1965.
As defined by Cowles and Bogert (194-4-), the "normal activity range"
for the lizards in this study is between 26-35 C»
The three cloacal
temperatures below 26 C were taken in the early morning when the lizards
first appeared and are not considered to be in the normal activity range.
It is assumed that the cloacal temperatures reflect the preferred tempera­
tures of the lizards as controlled by behavioral means (Ifeyhew, 1963).
The mean of all cloacal temperatures recorded is 29*8 C and is taken to
be the mean preferred temperature of Sceloporus graeiosus in the Norris
Geyser Basin,
this mean.
The three temperatures below 26 C were used in obtaining
When the temperatures are broken down into 2.9
G ranges,
approximately 59% of the cloacal temperatures fall within the 29 to 31*0 C
range (Table II).
Air and substrate temperatures taken along with the cloacal temperatures
of the lizards when captured are compared in Figures
4
and
5*
The temperatures
-18T A B L E II*
D i s t r i b u t i o n o f 32 Scelonorus cloa c a l t e m p e ratures
Temperature Range
H
$ Of Total
23 - 25.9
3
9.4
26 - 28,9
5
15.6
29 - 31*9
19
59.4
32 - 34*9
5
15.6
(C)
If o Sample Size
were, taken from the time the lizards were first seen in the morning
(about 8:00 a.m*) until they disappeared in the afternoon (about. 6:00 p.m*)
Capturing the lizards by chasing'may have had the effect of increasing the
body temperatures*
However, Mayhew '('1963) found that the body temperatures
of lizards were relatively unaffected by cha^in^^, andithis' is ,also''
assumed in the. present paper*
' -
Both the mean air temperature I foot above the ground (22*3 C) and the
mean substrate temperature (24*5 C) were lower than the mean cloacal
temperature.
There is a significant difference between the cloacal and
air temperatures and between the cloacal and substrate temperatures
(t-test, Pa*05)*
However, the difference between cloacal and substrate
temperatures is not as great as between cloacal and air temperatures.
A series of environmental temperatures taken in July, 1965, in six
selected sites, are presented in Table III.
These particular days were
chosen because the temperatures were taken at about the same time (between
-19-
Air
Figure 4.
Temperature
(C)
Cloacal temperatures of 32 lizards at time of capture versus
air temperatures (I ft. above surface) at site where lizards
were initially seen. The diagonal line connects points of
equal cloacal and air temperatures.
Cloeee I Tempe
-20-
Substrate
Figure 5»
Temperoture
(C)
Cloacal temperatures of 32 lizards at time of capture versus
temperatures of the substrate where lizards were initially seen.
The diagonal line connects points of equal cloacal and substrate
temperatures.
-21-
TABLE III,
Selected environmental temperature (C) in the Norris Geyser
Basin during July of 196$.
Thermocouple
I
4
Date
Time
7/1
3 :00 pm
2 3 .0
15.0
1 9 .2
18.6
1 9 .2
7/5
5:00 pm
24.4
2 5 ,5
22.8
2 2 .2
7 /6
3:45 pm
32.5
3 3 .9
35 .5
7/7
2:45 pm
3 0 .3
3 3 .6
7/8
2:45 pm
26.4
7 /9
3:00 pm
2
3
5
6
Max.
MLn.
3 8 .0
22.2
3 .3
25.0
4o.o
20.6
2 .8
2 7 .2
34 .2
4 9 .4
2 5 .6
2 .8
3 2 .8
2 9 .4
2 7 .2
3 5 .8
25.0
3.3
25.0
27.2
2 8 .3
33.1
4 7 .2
2 5 .0
6.1
32.2
31.1
31.1
29.4
4 0 .3
4 5 .0
26.1
3 .9
7/ll 3:30 pm
31.1
32.2
——
2 8 .3
4o.o
47.0
24.4
5.6
7/13 4:00 pm
29.4
2 8 .6
3 2 .2
2 4 .7
33.1
34.4
2 3 .9
-2.2
7/15 4:00 pm . 30.0
29.0
3 2 .0
29.O
34.0
4 8 .0 '
29.4
2.2
3:00 pm .34.0
31.5
31.5
2 8 .0
3 2 .0
4 3 .5
26.1
1.1
28.5
2 9 .4
2 6 .5
3 1 .8
42.8
24.8
3.1 ■
7 /2 3
Mean
2 9 .3
2;45 Pern, - 5:00 p 0m«) and were days when the lizards were active.
The
minimum and maximum air temperatures recorded one foot above the ground
for each day (24 hr. period) are also presented.
These temperatures can he interpreted as being temperatures the
lizards would encounter in their active season in the Norris Geyser Basin.
Thermocouple I was located in a siliceous sinter area which the lizards
seldom used.
Although the mean temperature of 29»3 closely approximates
-22-
the mean cloacal temperature of the lizards it is apparently not signifi­
cant <, since at no time during the study were lizards' seen to be utilizing
the area*
Thermocouple 2 measured the air temperature in a lodgepole - juniper
area at the base of an easterly exposed rhyolite slope and thermocouple 4
measured the air temperature about 50 feet up the rhyolite slope*
Both
the means for the two thermocouples were lower than the cloacal mean*
The
mean for thermocouple 2 (28*5 C) was higher than the mean for thermocouple
4 (26*5 C) because of the protection afforded by the vegetation and
consequently there was little mixing of the air*
Thermocouple 5 .measured the surface temperature of a rock on which
lizards were seen basking.
This probably is the most significant in that
it represents temperatures the lizards would most frequently encounter
while attempting to reach their preferred body temperature.
Thermocouple
3 (mean 28,5 C) may also be significant in this respect, since this
thermocouple measured the ground temperature in a lodgepole - juniper area
which the lizards were seen to frequent in late afternoon.
Thermocouple 6 was located under a rock which several lizards had been
seen using as a hiding spot.
It was later discovered that a small, inter-
mittant steam vent was located there, Although lizards used it at times,
temperatures in the high 4 0 !s would make it prohibitive for continuous use.
The minimum and maximum air temperatures merely provide a range of
daily air temperatures *
The thermometer was located in a spot where it
was subject to fluctuations caused by the wind.
-23-
Population
studies
No movement of marked lizards between areas in the Norris Geyser Basin
was observed during the study. ■Movement within the study areas themselves
also, seemed to be quite limited.
Several marked individuals were found
repeatedly in the same location.
One particular adult female was captured
in Area 3 and marked with yellow paint on June 23; 1965»
capture her tail was accidently broken off.
At the time of
Since she was the only marked
adult in Area 3 with a broken tail, positive identification was possible.
On subsequent visits to the area this lizard was found 17 out of 25 times.
Each time she was was found she was either on, near or under,a large flat
rhyolite rock located on the southeast edge of the rhyolite outcrop in
Area 3«
This would seem to indicate that at least some lizards have
preferred sites within a given area.
The young-of-the-year were typically found on the periphery of what
could be considered to be the main population centers.
and this was most noticeable here.
outcropping or knoll.
Area 3 is small,
In the center of this area is a rhyolite
Surrounding this is an open area with only
scattered rocks and young lodgepole growth for cover.
The majority of
juvenile and adult lizards found in Area 3 were located on the outcropping,
whereas when the young-of-the-year appeared (August) they were found in the
sparsely covered area
surrounding the outcropping,
■Estimates of the lizard populations in the study areas were made by
using the Lincoln Index method.
Each count was obtained by moving through
the areas slowly, observing those sites in which lizards were frequently
-24-
seen and hy overturning any rocks which might serve as hiding places.
In
most of the counts the author was assisted by at least one other person.
This resulted in a more thorough coverage of the areas, especially the two
larger areas.
It was estimated that under normal conditions the lizards retained their
dorsal paint markings for a period of one month.
Therefore, only those
lizards marked within one month prior to a given estimate were considered
to be part of the marked population,
As previously mentioned there were a
number of marking periods each summer.
Within -a week after each marking
period a population estimate was made.
The population estimates are pre­
sented in Table IV,
The population estimates indicate that the largest population of lizards
was in Area I,
A population estimate taken on September 2, 1964, indicates
that there were 120 lizards in .Area I.
Bo marked lizards were seen during
a count made on August 25, 1965, in Area I,
Had one marked lizard been
seen on this count, the population estimate would have been in excess of
200»
This may indicate that the population estimates are low, and that.the
actual populations are somewhat higher than the estimates imply.
Since all the estimates a r e .in a large part dependent upon the author's
ability to spot the lizards, the first estimates made in 1964 are probably
not as accurate as those made later.
The smallest over-all variation in the
estimated population size occurs in Area 2 in 1964,
However, since Area 3
was small, the counts taken there were quite thorough, and the resultant
population estimates are probably the most accurate.
-25-
TABLE IV.
Population estimates by area for 1964 and 1965. The parentheses
indicate the total number of lizards seen during each population
count.
Area I
Area 2
25 ( 7)■
30 ( 6 )
Area 3
1964
July 12
20 ( 5 )
July 13
July 19
45 ( 9)
July 29
(17)
July 30
Aug. 24
35 (1 3 )
18
70 (14)*
( 7 )*
33 (10)*
Aug. 25
Sept 0 2
44 (11)
120
(1 6 )*
35 ( 7 ) *
1265
June 15
34 (17)
12 ( 3)
Il ( 7)
June l6
June 24
40 ( 8 )
July 11
4o (15)
21 ( 7)
27 ( 9 )
29 (1 2 )
July 29
July 30
30 (1 0 )
60 (20)
16 ( 6 )
42 (15 )*
Aug 0 12
Aug. 13
57 ( 1 9 ) *
Aug. 25
- (1 0 )*
30 ( 1 0 ) *
Aug.. 26
44 ( 7 )*
Sept. 4
37 (H)*
-■ Sept0 5
99 ( H ) *
* Y o u n g - o f - t h e - y e a r p r e s e n t in p o p u l a t i o n count.
-26With the exception of Areas 2 and 3 in 1964, Table IV shows an apparent
increase in population sizes for all areas after mid-August,
This apparent
increase corresponds with the appearance of the newly-hatched young.
In
1964 the young-of-the-year were first seen on August 15th and in 1965 they
were first seen on August 12th,
The total number of lizards marked during the summers of 1964 and
1965 are presented in Table V,
TABLE V,
Total number of lizards marked by area in 1964 and 1965,
Area I
Area 2
Area 3
1964
26 ,
18
9
1965
40
20
21
DISCUSSION
The distribution of S. graeiosus in Yellowstone National Park is
seemingly limited to areas near thermal basins.
The lizards are rarely
found in the actual thermal basins, but rather on the timbered rhyolite
slopes immediately surrounding areas in which there are active geysers
and hot springs.
The thermal basins are characterized by boiling springs
and pools around which are deposits of siliceous sinter (SiOg),
These
siliceous sinter areas are characterized by the lack of any vegetative
cover,
Blair (i960) noted that a paved highway with its associated
cleared area and an open field proved to be partial barriers to dispersal.
The siliceous sinter areas which the lizards rarely frequented in the
Norris Geyser Basin are open expanses and are probably comparable to
BlairfS highway and open field, i,e., they afford little cover and are
undesirable lizard habitats.
Since lizard populations were not found in areas in which there was
no thermal activity, their presence in Yellowstone seems to be related
to the presence of the thermal activity.
however.
This is difficult to prove,
If the activities of the lizards were determined only by
soil temperatures as reflected by thermal activity, they would probably
be active in some periods during late fall, winter or early spring,
No
lizards were found during these periods in Yellowstone, although soil
temperatures in the thermally active sections were probably high enough
to support lizard activity since insects in these areas were active.
This observation tends to support Mayhew (1963), Fitch (1955).» and others
in that lizard hibernation is an innately controlled mechanism,
However,
- 28-
the warm soil temperatures present in these areas permit the lizards to
achieve "body temperatures allowing them to emerge earlier in the spring
then would otherwise he possible.
Since the growth period in Yellowstone
is short, early spring emergence is important for sufficient fat storage.
Mueller (1967) agrees with this premise.
The active season for lizards in Yellowstone is probably five
months at maximum since weather conditions usually prohibit lizard
activity from mid-September to May.
Stebbins (1944) in his study of
S. graciosus gracilis in Lassen Volcanic national Park, California,
estimated the activity period at five to six' months.
His study was con­
ducted at an elevation of 6,000 feet, whereas the present study was
conducted at an elevation of about 7,600 feet.
The mean preferred field temperature of 29.8 C for 8 . graciosus in
the Horris Geyser Basin is considerably lower than reported values in
other areas of its distribution.
Bogert (1949) gives 36.0 C as the mean
preferred field temperature of 8 . graciosus, while Lieht (1965) gives
35-3 G as the mean laboratory temperature.
Brattstrom (1965) gives
34.9 C as the mean temperature for S. g. gracilis.
Mueller (1967)
found that lizards from the Norris Geyser Basin placed in a thermal
gradient box chose temperatures approximating those encountered in the
field.
The reason for the lower preferred mean temperature of the lizards
in the Norris Geyser Basin is unknown.
Mueller (1967) suggests it is
either due to genetic differences or is a result of acclimation.
The mean cloacal temperature of S. graciosus was significantly
-29-
higher than the means of either the air or substrate temperatures taken
at the sites of capture.
Cole (1943) felt, that lacking a radiant energy-
source, the substrate was more important than the air temperature in
determining lizard body temperatures,
may be true.
Present data indicate that this
However, in only 2 out of 32 instances was the substrate
temperature higher than the corresponding cloacal temperature.
Tempera­
tures taken on a basking rock in the Harris Geyser Basin were generally
higher than the mean preferred temperature of the lizards.
This rock
was heated by radiant energy as would be the lizards basking on it.
This
substrate would be important however, to the lizards when the sun was down
or under clouds, etc., in maintaining their preferred body temperature •
since it would lose its heat slowly.
The author then concurs with
Mueller (1967) in that the lizards generally use radiant energy to raise
their body temperatures, but also feels that thermal activity may play a
role, in helping to maintain higher substrate temperatures than normal,
which in turn would help the lizards through unseasonal cold spells.
Memibers of the genus.Sceloporus seem to have a limited home range.
Stebbins (1944) found that females of S» g. gracilis traversed an average
of 59.0 feet during the active season, while males traversed an average
of 82.1 feet.
Blair (i960) found that S. olivaceus males and females had
average home ranges corresponding to squares 85.8 feet and 56.O feet on a
side, respectively.
Ho measurements on home range were made during the
present study, but no movement between the populations was observed,
indicating that the home range was limited.
Also, lack of movement
between the three areas at Horris can be attributed to Tantalus Creek.
-30-
The creek apparently serves as a barrier to movement since it consists
mostly of run-off water from thermal features, and its temperature
(42 - 50 C) at most times is near or above the critical thermal maximum
as determined by Mueller (1967) for the lizards in the Norris Geyser Basin.
The preference by a lizard for a certain site within a home range was
observed in the Norris study areas.
This behavior has also been noted
by Stebbins (1944), Blair (i960) and others.
Lizards which were typically
seen in a specific site day after day were usually basking, and this may
be the reason for the selection of the site*
The dispersion of the young away from the areas generally frequented
by adults is apparently normal behavior.
Woodbury and Woodbury (1945)
also noted this type of behavior in their study of S. graciosus in Utah,
Blair (i960) noticed this behavior in S. olivaceus and attributed it to a
difference in the living habits between the young and adults; i.e.,
"juvenile lizards tend to occupy different vegetational types of habitat
than the adults and to use different basking sites, and so they have
little contact with the adults."
In the Norris Geyser Basin the young
did not occupy a different vegetational type, but the vegetation in the
areas in which they were found was much less dense and generally lowergrowing than the vegetation characteristically occupied by adults.
No data were obtained on egg-laying in the present study, but the
yDung-of-the-year were seen on comparable dates each year.
In 1964, the
first young were observed on August 15th, ,and in 1965 they were first
seen on August 12th.
In Utah, Woodbury and Woodbury (1945) found the
-31-
incubation period of S, graeiosus eggs varied, but two months was about the
maximum*
This would indicate that the major period of egg-laying in Norris
Geyser Basin occurs in early June and perhaps extends to July*
This agrees
with Stebbins (19^4) except that the newly hatched lizards appeared earlier
in Yellowstone than they did in Lassen*
This is probably due to the
difference in altitude and the shorter time which the lizards were active
in Yellowstone compared to California*
The lizards were broken into age classes on the basis of snout-vent
length.
Three groups were recognized:
young-of-the-year, juveniles and
adults, although the lizards classified as adults also exhibited some
growth,
Mueller (1967), using toe-clipped lizards, recognized four age
classess:
and older.
juveniles, one year olds, two year olds, and three years old
In the present study no distinction was made between the two
and three year old groups.
The largest male and female lizard measured (snout-vent length) was
54 and 58 mm respectively, while the young-of-the-year averaged about 26
mm.
Stebbins (1944) also found the young-of-the-year to be between 25-
26 mm in length and the largest male and female he measured were 55»5 mm
and 57.5 mm in length.
Woodbury and Woodbury (1945) found that the ovarian and testicular
cycles began when the lizards were about one-year old.
This means that
the lizards classified as young-of-the-year and juveniles in the present
study are sexually immature,
Blair (i960) suggests that those species
which reproduce only once a year (such as S. g. gracilis in Lassen Park)
-32-
have a considerably longer life span than those which reproduce several
times a year (such as S. olivaceus in his study).
The data from Table I
indicate that the lizards in the Norris Geyser Basin are probably longlived (55 adults ■: 62 juveniles and young-of-the-year in a random sample).
The presence of Sceloporus graciosus in Yellowstone National Park is
unique when one considers the elevation, latitude and general weather
conditions.
How important the thermal activity is to the lizards found
here has not been fully ascertained.
Future research should be oriented
toward determining this relative importance.
LITERATURE CITED
Beal^ M. D. 1951» The occurrence and seasonal activity of vertebrates in
the Norris and Gibbon Geyser Basins of Yellowstone National Park.
Unpubl, Master's thesis. Utah State Agr. College. 58 pp.
Blair, W. F. i960. The rusty lizard, a population study.
Texas- Press. 185 pp.
University of
Bogert, Ce M. 19^9* Thermoregulation and eccritic body temperatures in
Mexican lizards of the genus Sceloporus. An, Inst. Biol. Mexico
20 ;kl5-k26.
Booth, W. E. 1950. Flora of Montana, Part I. Conifers and Monocots.
Research Foundation at Montana State College, Bozeman, Montana. 232 pp
* and J. C. Wright. 1966. Flora of Montana, Part II.
Dicotyledons. Montana State College, Bozeman, Montana. 305 pp.
Boyd, F. Ro 1961. Welded tuffs and flows in the rhyolite plateau of
Yellowstone Park, Wyoming. Geol. Soc. America, Bulletin 72:387-426.
Brattstrom, B. H. 1965.
Nat. 73:376-422.
Body temperatures of Reptiles.
Amer» Midi.
Cole, L. C. 1943o Experiments on toleration of high temperatures in
lizards with reference to adaptive coloration. Ecology 24:94-108.
Cowles, R. B. and C. M 0 Bogert0 1944. A preliminary study of the
thermal requirements of desert reptiles. Amer. Mis. Nat. Hist.
Bulletin 83 :265-296.
Dasmann, R 0 F. and R. D 0 Tabor. 1955* A comparison of four deer census
methods. California Fish and Game 4l (3) :225-228.
Fitch, H. S. 19550 Habits and adaptations of the Great Plains Skink
(Eumecas obsoletus) Ecol. Monogr. 25(l) :59-83*
Geiger, 'R. 1957® Tha climate""near the ground.
Press, Cambridge, Mass, xxi + 494 pp.
Li, J. C 0 R. 1964. Statistical Inference.
Inc., Ann Arbor. 658 pp.
2nd Ed.
Vol. I.
Harvard Univ.
Edwards Brothers,
Licht, P. 1965® Effects of temperature on heart rates of lizards
during rest and activity. Physiol. Zool. 38:129-137.
Mayhew, W. W. 1963. Temperature preferences of Sceloporus orcutti.
Herpetpligica 18(4) :217-233«
Mueller, C. F e 1967» Temperature and energy characteristics of the ■
Sagebrush Lizard in Yellowstone National Park, Unpubl. Doctor's
thesis. Montana State University, Bozeman, Montana. 38 PP«
Stebbins, B. C. 1944. Field notes on a lizard, the mountain swift,.
with special reference to territorial behavior. Ecology 25: 233-245.
__________ ___, 1954. Amphibians and reptiles of western North America.
McGraw-Hill. New York. 528 pp.
Turner, F. B. 1955 = Reptiles and amphibians of Yellowstone National
Park. Yellowstone Interpretive Series, No. 5, Yellowstone Library
and Museum Association, pp. 18-20.
U. S. Weather Bureau. 1965, 1966. Climatological Data, Montana,
Monthly summaries for May and June, 1965, 1966. U. S. Department
of Commerce, Weather Bureau, Asheville, North Carolina.
Woodbury, M. and A. M. Woodbury. 1945» Life-history studies of the
sagebrush lizard Sceloporus g. graciosus with special reference
to cycles.in reproduction. Herpetologica 2:175-196»
Yarrow, H. C. 1883» Checklist and Catalogue of N. Amer. Reptilia and
Batrachia in the U. S, Nat, Mus. U, 8» Nat. Mus. Bull. 24.
Yeager, D. 1926. Miscellaneous notes.
Vol. III., 4:7»
Yellowstone Nature Notes,
_________, 1929* Reptiles of Yellowstone Park with notes on the
Amphibia. Unpubl„ manuscripts, 12 pp. typed. Yellowstone Research
Library.
MONTANA STATE UNIVERSITY LIBRARIES
762 1001 1994
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