Proceedings of the 4th Big Thicket Science Conference
2009 Southeastern Naturalist 8(Special Issue 2):63–76
Habitat Selection by Anolis carolinensis (Green Anole) in
Open Pine Forests in Eastern Texas
Richard R. Schaefer1,*, Robert R. Fleet2, D. Craig Rudolph1,
and Nancy E. Koerth1
Abstract - We initiated a mark-recapture study to determine the effects of shrub
density on Anolis carolinensis (Green Anole) populations. Green Anole perch site,
shrub species, and shrub volume preferences were also examined. We established two
study plots of different shrub densities in open pine forests on the Angelina National
Forest in eastern Texas. In late spring, the Green Anole population at the higher
shrub-density plot was estimated to be 16 times greater than the population at the
lower shrub-density plot. Green Anoles most commonly perched on live shrubs, but
exhibited very little preference or avoidance of any particular species of live shrub
or shrub-level vine. However, shrubs used by Green Anoles were 4–6 times greater
in volume than plot averages.
Introduction
Anolis carolinensis Voigt (Green Anole) is an abundant arboreal lizard
with a wide distribution in the southeastern United States (Conant and Collins
1998). It is preyed upon by numerous taxa within its range, especially
during warmer months when it is most active (Arndt 1995, Corey 1988, Kennedy
1964, Yosef and Grubb 1993). We were particularly interested in the
importance of Green Anoles in the diet of Falco sparverius paulus (Howe
and King) (Southeastern American Kestrel), a subspecies of conservation
concern. Thus, this study was closely associated with ongoing research
where the Green Anole has proven to be the single most common prey item
delivered to nestling Southeastern American Kestrels in eastern Texas (R.R.
Schaefer, unpubl. data). Breeding Southeastern American Kestrels in Florida
were also reported to feed heavily on anoles and other lizards (Bohall-Wood
and Collopy 1987, Smallwood and Bird 2002).
Green Anoles and Southeastern American Kestrels occur together in relatively
open pine communities in the southeastern United States. Historically,
periodic wildfire was the principal disturbance mechanism that maintained
the open character of these pine communities. Strictly controlled prescribed
fire has now largely replaced wildfire throughout much of the southeastern
United States. Varying densities of shrub growth develop following these
fires as plants resprout. The density of shrubs at a given site is dependent
1Wildlife Habitat and Silviculture Laboratory, Southern Research Station, USDA,
Forest Service, 506 Hayter St., Nacogdoches, TX 75965 (maintained in cooperation
with the Arthur Temple College of Forestry, Stephen F. Austin State University). 2Department
of Mathematics and Statistics, Stephen F. Austin University, Nacogdoches,
TX 75962. *Corresponding author - rschaefer01@fs.fed.us.
64 Southeastern Naturalist Vol. 8, Special Issue 2
on soils, moisture, and fire frequency and intensity, among other factors
(Gilliam et al. 1993, Glitzenstein et al. 1995). Green Anoles prefer dense
shrubbery in more open areas (Dundee and Rossman 1989). Open pine
communities with a greater shrub density may harbor a greater abundance
of anoles and provide higher quality foraging habitat for kestrels during
seasons when anoles are most active.
Numerous studies of Anolis lizards, especially Caribbean species, have
sought answers to both interspecific and intraspecific habitat-related questions
(Irschick et al. 2005, Jenssen 1973, Rodríguez-Robles et al. 2005,
Schoener 1975), but to our knowledge, none have addressed the relationship
between shrub density and population size. We estimated the Green
Anole population size and characterized habitat use at two upland pine sites
in eastern Texas. We suspected that greater shrub density would correspond
with higher anole populations by providing more perch sites, increased
food resources, and greater concealment from predators. We were primarily
interested in relationships between shrub density and Green Anole population
size, but we also examined anole perch site, shrub species, and shrub
volume preferences.
Field-site Description
We established two 0.5-ha study plots, separated by a distance of approximately
2.7 km, on the southern Angelina National Forest in eastern
Texas. Because of our interest in the predator-prey relationship between
Southeastern American Kestrels and Green Anoles, we selected plots within
known kestrel foraging areas. Plots were located within open pine forests
dominated by the fire-adapted Pinus palustris P. Mill. (Longleaf Pine), and
receive periodic prescribed fires by forest managers. One plot contained a
higher density of shrub-level vegetation (shrubs and shrub-level vines) and
the other had a much lower density. Hereafter, they will be referred to as
the “high-density plot” and the “low-density plot.” Prior to study initiation
in May 2004, the most recent prescribed fire occurred on 31 January 2001
at the high-density plot and on 1 February 2001 at the low-density plot.
Shrub-level vegetation at the high-density plot was not contiguous and was
irregularly dispersed throughout the plot.
Controlled fires maintained an open character by impeding the encroachment
of woody shrub and mid-story vegetation of non-Longleaf Pine species
(Platt et al. 1988, Provencher et al. 2001). A portion of the mid-story vegetation
survived these fires, depending on the species as well as timing and
intensity of the fire (R.R. Schaefer, pers. observ.). However, most shrub species
were killed back to ground level since they are much smaller in diameter
and more vulnerable to even low intensity fires, resulting in the resprouting
of an even-aged layer of woody, shrub-level vegetation (R.R. Schaefer, pers.
observ.). Soil and moisture further infl uenced the density and species composition
of woody vegetation (Gilliam et al. 1993). Ground-cover vegetation
was more prevalent in areas where fewer shrub and mid-story plants allowed
2009 R.R. Schaefer, R.R. Fleet, D.C. Rudolph, and N.E. Koerth 65
sunlight to penetrate to ground level (Masters et al. 1996). Greater shrub
and mid-story densities, especially hardwoods, resulted in more area of bare
ground and leaf litter.
Methods
During mid-summer of 2004, we conducted a complete census of all
shrub, mid-story, and canopy plants within each plot. Woody vegetation was
categorized based on height: ground level (less than 0.5 m), shrub (≥0.5 m and less than 3
m), mid-story (≥3 m and below the canopy), and canopy. We used a 1-m pole
marked with 0.1-m increments to measure the height (m) and width (m) of
each live, woody shrub-level plant (shrubs and vines) within each plot and
calculated the percent of total shrub volume (height x width2) occupied by
each shrub-level species. A clinometer was used to measure the height (m)
of each mid-story tree, and calipers were used to obtain diameter at breast
height (DBH; cm) for each mid-story and canopy tree. We divided each plot
into four equal subplots. At the center point of each subplot, we measured
canopy height (m) with a clinometer; estimated percent ground cover of
woody vegetation, herbaceous vegetation, and bare ground/leaf litter; and
used a one-factor metric basal area prism to measure basal area (m2/ha) of
pine canopy, hardwood canopy, pine mid-story, and hardwood mid-story.
All Green Anole data were collected during late spring/early summer
(11 May–2 July) and late summer (1–13 Sept.) of 2004. Hereafter, these
time frames will be referred to as “late spring” and “late summer.” Markrecapture
data were obtained during late spring (11–27 May) and late
summer (1–13 Sept.) at the high-density plot, and during the late spring (25
May–4 June) at the low-density plot. There were 5 mark-recapture sampling
events in the high-density plot during both late spring and late summer, and
3 sampling events in the low-density plot during late spring. Two to four
observers conducted a search for Green Anoles within the entire plot, from
ground level up to mid-story level, during each sampling event. The upper
portion of canopy trees was not included in the searches since we could not
adequately locate anoles at that height, but the lower portion of canopy tree
boles (less than 5.0 m above ground) was searched. Green Anoles were captured by
hand and ventrally marked in numerical order using a nontoxic permanent
marker. Those escaping capture were recorded as such. We measured snoutto-
vent length (svl) to the nearest 1.0 mm on all captured anoles. Those measuring
≥40 mm were considered adult, and those less than 40 mm were considered
juvenile (Jenssen et al. 1998). Individuals escaping capture were visually
determined to be adult or juvenile. Sex was not consistently recorded since
it was not relevant to our study objectives. However, we did record the sex of
very obvious individuals (e.g., large, displaying males). We recorded Green
Anole perch height (m) where first sighted, perch site, and perch-site plant
species for each individual observed, including those that escaped capture.
We noted 14 different perch sites (Table 1). We used paired t-tests (paired
by plot and date) to compare adult and juvenile perch heights, and included
66 Southeastern Naturalist Vol. 8, Special Issue 2
only those dates when both age categories were observed. We also recorded
the height (m), width (m), and subsequently calculated the volume (m3) of
all live, shrub-level plants on which Green Anoles were observed.
We assumed mark-recapture data were collected over short enough time
spans within each season (17 and 13 days during late spring and late summer,
respectively, at the high-density plot; 11 days during late spring at the lowdensity
plot) that the effects of migration, mortality, and recruitment at each
plot were negligible. Thus, we assumed plot populations of Green Anoles
were closed (Seber 1986, 2001). We used the program CAPTURE (Otis et al.
1978) to select the appropriate capture model and estimate population size
within each plot. Search time for a given day varied, and all searches were
conducted between 1015 and 1616 within cloud cover (0–100%) and temperature
(23.5–33.0 °C) ranges conducive to Green Anole activity. Temperature
was more important than cloud cover in infl uencing anole activity. We experienced
good success in locating anoles when the percent cloud cover was high
as long as temperatures were at least within the range given above.
We determined Green Anole preference and avoidance of various shrublevel
species by calculating the selection index and confidence limits for
Manly et al.’s (1993) Design II, and conducting a complete census of avail-
Table 1. Perch sites used by Anolis carolinensis (Green Anole) at two study plots in eastern Texas.
Low shrub
High shrub density plot density plotA
Late spring Late summer Late spring
Perch site % (# observations) % (# observations) % (# observations)
Shrub vegetationB
Live shrub 61.8 (115) 67.3 (70) 60.0 (21)
Dead shrub 1.6 (3) 2.9 (3) 2.9 (1)
Live within dead shrubC 2.2 (4) 4.8 (5) 0.0 (0)
Woody vine at shrub level 3.8 (7) 6.7 (7) 28.6 (10)
Debris lodged in live shrub 1.1 (2) 1.0 (1) 0.0 (0)
Mid-story vegetationD
Pine midstory 0.5 (1) 0.0 (0) 0.0 (0)
Hardwood midstory 16.1 (30) 3.9 (4) 2.9 (1)
Woody vine at midstory level 0.0 (0) 1.9 (2) 0.0 (0)
Canopy pine trunk 2.2 (4) 2.9 (3) 0.0 (0)
Live woody ground vegetationE 1.1 (2) 4.8 (5) 0.0 (0)
Bracken FernF 1.1 (2) 0.0 (0) 0.0 (0)
Tree stump 1.1 (2) 1.9 (2) 2.9 (1)
Log/limb on ground 5.4 (10) 1.0 (1) 2.9 (1)
Bare ground/leaf litter 2.2 (4) 1.0 (1) 0.0 (0)
Total observations 100.0 (186) 100.0 (104) 100.0 (35)
ANo data for late summer.
BShrubs = ≥0.5 m and less than 3.0 m in height.
CResprouting shrub following a prescribed fire, with the live portion at shrub level and the firekilled
portion still standing.
DMidstory = ≥3.0 m in height and below canopy.
EGround = less than 0.5 m in height.
FPteridium aquilinum (L.) Kuhn (Bracken Fern).
2009 R.R. Schaefer, R.R. Fleet, D.C. Rudolph, and N.E. Koerth 67
able resources. In this case, “available resources” refers to volume of all live
shrub-level plant species. In these analyses, if the 95% confidence interval
around the selection index includes 1.00, the species was considered neutral
(i.e., neither preferred nor avoided). If the upper confidence limit was less
than 1.00, the species was considered avoided. If the lower confidence limit
was greater than 1.00, the species was considered preferred. However, those
species with an upper or lower confidence limit between 0.90 and 1.10 were
considered “borderline avoided” or “borderline preferred,” respectively.
Green Anoles escaping capture and marking were omitted here since individuals
must be identifiable for these calculations.
We calculated the mean width, height, and volume of all available shrublevel
woody plants in each plot. We compared the means to similar values
calculated for those plants harboring Green Anoles in an effort to identify
shrub-structure preferences. Because all woody vegetation was measured
(not sampled) in each plot, statistical comparisons were unnecessary.
Results
Canopy height was similar between plots, but the high-density plot contained
1.5 times more pine canopy trees than the low-density plot (Table 2).
There were 66 hardwood mid-story trees in the high-density plot versus only
Table 2. Forest habitat measurements at two Anolis carolinensis (Green Anole) mark-recapture
study plots in eastern Texas.
Habitat variable High shrub-density Low shrub-density
Canopy height (m)A 24.6 25.1
Pine canopy basal area (m2/ha)A 22.0 15.6
Total pine canopy trees 81 52
Pine canopy diameter at breast height (cm)B 41.0 40.5
Pine mid-story basal area (m2/ha)AC 2.5 1.8
Total pine mid-story treesC 32 37
Pine mid-story diameter at breast height (cm)BC 11.7 15.8
Pine mid-story height (m)BC 12.0 15.9
Hardwood canopy basal area (m2/ha)A 0.3 0.0
Total hardwood canopy trees 1 0
Hardwood canopy diameter at breast height (cm)B 42.5 0.0
Hardwood mid-story basal area (m2/ha)AC 2.9 0.0
Total hardwood mid-story treesC 66 1
Hardwood mid-story diameter at breast height (cm)BC 14.9 30.5
Hardwood mid-story height (m)BC 9.2 11.4
Total shrubs and shrub-level vinesD 1517 598
Woody ground cover (%)AE 13.7 42.5
Herbaceous ground cover (%)AE 16.3 30.0
Bare ground/leaf litter (%)AE 70.0 27.5
AThe mean for this variable was derived from measurements taken at 4 subplots within each
shrub plot.
BThe mean for this variable was calculated using the total number of plants within each shrub plot.
CMidstory = vegetation ≥3.0 m in height and below canopy.
DShrub = vegetation ≥0.5 m and less than 3.0 m in height.
EGround = vegetation less than 0.5 m in height.
68 Southeastern Naturalist Vol. 8, Special Issue 2
1 in the low-density plot. The number of pine mid-story trees was slightly
greater in the low-density plot (37 versus 32). Canopy hardwoods were nonexistent
in the low-density plot, and only one occurred in the high-density
plot. The total number of live shrubs and shrub-level woody vines was more
than 2.5 times greater in the high-density plot than in the low-density plot.
Both woody and herbaceous ground covers were better developed in the lowdensity
plot, perhaps due to the near absence of hardwood mid-story. Bare
ground/leaf litter cover was 2.5 times greater in the high-density plot where
hardwood mid-story was much more common.
Totals of 37 and 15 woody shrub-level species were found in the highdensity
and low-density plots, respectively, indicating greater species
richness in the former (Table 3). A species’ abundance did not necessarily
correlate with the percent of volume occupied by that species within a plot.
For example, Sassafras albidum (Sassafras) made up 16% (242 plants) of
total shrubs in the high-density plot, making it the most abundant species
there. However, it accounted for only 2.6% of the total shrub volume in that
plot. Conversely, Callicarpa americana (American Beautyberry) made up
3.8% (58 plants) of all shrubs in the high-density plot, yet accounted for
14.5% of the total shrub volume. Similarly, Rhus copallina (Shining Sumac)
made up 45.3% (271 plants) of total shrubs in the low-density plot, but accounted
for only 15.5% of the total shrub volume. Vitis aestivalis (Summer
Grape) made up only 6.9% (41 plants) of total shrubs in the low-density plot,
but accounted for 24% of the total shrub volume.
Green Anole abundance was much greater at the plot with a higher density
of shrubs (Table 4). During mark-recapture sampling events, 87 and 74
individuals were marked at the high-density plot during late spring and late
summer, respectively. Eight were marked at the low-density plot during late
spring. The program CAPTURE selected model Mt (capture probabilities
vary with time) to derive a Green Anole population estimate of 211 at the
high-density plot during late spring. The model Mo (capture probabilities are
constant) was selected for calculations of Green Anole populations of 160
at the high-density plot during late summer and 13 at the low-density plot
during late spring.
Green Anoles were observed on live shrubs much more often than any
other perch site in both plots during late spring and in the high-density plot
during late summer (Table 1). No late summer data are available for the lowdensity
plot. Green Anoles at the high-density plot were found on live shrubs
61.8% (n = 115) of the time followed by hardwood mid-story at 16.1% (n =
30). Adult males, often displaying, accounted for 56.7% (n = 17) of anole
observations on hardwood mid-story trees. Eight juveniles accounted for
only 7% of all marked individuals at the high-density plot during late spring.
Green Anole age distribution shifted dramatically by late summer at the
high-density plot, where juveniles accounted for 71.6% (n = 53) of marked
individuals. Live shrubs remained the most frequently observed perch site
at 67.3% (n = 70), followed by woody vines at shrub-level at 6.7% (n = 7).
2009 R.R. Schaefer, R.R. Fleet, D.C. Rudolph, and N.E. Koerth 69
Observations on hardwood mid-story vegetation were reduced to 3.9%
(n = 4) of the total. Only adults (n = 10) were captured at the low-density plot
prior to 28 June. Juveniles made up 50% (n = 5) of initial captures (n = 10) at
the low-density plot from 28 June to 2 July. Live shrubs were again the most
commonly used perch site at the low-density plot at 60% (n = 21) followed
by woody vines at shrub level at 28.6% (n = 10) of total observations.
Juvenile Green Anoles (n = 8) captured at the high-density plot during
late spring had a mean svl of 37.6 mm, and we found no significant difference
between adult perch height (mean = 0.72 ± 0.03 m) and juvenile perch height
(mean = 0.65 ± 0.13 m, t = 0.60, df = 5, P = 0.57). All juveniles (n = 5) captured
at the low-density plot were found during early summer (28 June–2 July) and
had a mean svl of 24.0 mm. Adult perch height (mean = 0.65 ± 0.13 m) was
not significantly greater than juvenile perch height (mean = 0.41 ± 0.16 m, t =
0.81, df = 2, P = 0.50) at the low-density plot. Juveniles (n = 53) captured at
the high-density plot during late summer had a mean svl of 31.5 mm, and adult
perch height (mean = 1.0 ± 0.06 m) was significantly greater than juvenile
perch height (mean = 0.77 ± 0.09 m, t = 6.73, df = 4, P = 0.003).
Green Anoles exhibited very little preference for, or avoidance of, any
particular species of live shrub or shrub-level vine. However, many species
were too uncommon within the plots to detect preference or avoidance by
anoles. Many other shrub-level species were considered neutral in preference
since the number of expected anole observations was similar to the number
of actual observations. Only 17 of 37 available shrub-level species were used
by Green Anoles at the high-density plot during late spring. Of the unused
species, only Asimina parvifl ora (Dwarf Pawpaw) was common enough to
expect to be used at least once. Of the used species, Quercus stellata (Post
Oak) and Muscadine Grape were considered avoided by Green Anoles and
Quercus marilandica (Blackjack Oak) was ranked as preferred. Ilex vomitoria
(Yaupon) was considered borderline avoided (upper confidence limit for
the selection index was 1.00), and Carya texana (Black Hickory) was borderline
preferred (lower confidence limit for the selection index was 0.93).
Twelve species used by Green Anoles were ranked as neutral.
Green Anoles again used only 17 of 37 available shrub-level species at
the high-density plot during late summer. Of the unused shrub-level species,
only Sassafras occurred in sufficient volume to expect use by anoles. Yaupon
was ranked as avoided and Black Hickory was considered preferred. Fifteen
species used by Green Anoles were ranked as neutral.
Seven of 15 available shrub-level species were used by Green Anoles at
the low-density plot during late spring, but none were ranked as preferred.
Of the unused species, only Shining Sumac occurred in sufficient volume
to expect use by anoles. Quercus incana (Bluejack Oak) was borderline
avoided (upper confidence limit for the selection index was 1.00). Six species
used by Green Anoles were ranked as neutral.
Shrubs and shrub-level vines harboring Green Anoles averaged wider,
taller, and greater in volume than available shrubs present in each plot in
70 Southeastern Naturalist Vol. 8, Special Issue 2
Table 3. Percent of total plants, number of plants, and percent of total volume of live shrub-level woody vegetation by species and frequencies of use by Anolis
carolinensis (Green Anole) at two study plots in eastern Texas.
High shrub-density plotB Low shrub-density plot
% of total % (# anole % of total % (# anole
Shrub speciesA % (# of plants) volume observations)C % (# of plants) volume observations)C
Asimina parvifl ora (Michx.) Dunal (Dwarf Pawpaw) 3.1 (47) 1.46 0.5 (1) 0.5 (3) 0.06 0.0 (0)
Berchemia scandens (Hill) K. Koch (Alabama Supplejack) 0.1 (1) 0.03 0.0 (0) 0.0 (0) 0.00 0.0 (0)
Callicarpa americana L. (American Beautyberry) 3.8 (58) 14.48 17.3 (36) 7.5 (45) 32.89 45.2 (14)
Carya texana Buckl. (Black Hickory) 9.6 (145) 9.25 15.8 (33) 0.8 (5) 1.63 3.2 (1)
Chionanthus virginicus L. (Fringetree) 0.1 (2) 0.25 0.5 (1) 0.0 (0) 0.00 0.0 (0)
Cornus fl orida L. (Flowering Dogwood) 2.6 (40) 1.10 1.9 (4) 0.2 (1) 1.10 0.0 (0)
Crataegus spp. L. (hawthorn species) 0.5 (8) 0.10 0.5 (1) 0.0 (0) 0.00 0.0 (0)
Gelsemium sempervirens (L.) St. Hil. (Carolina Jessamine) 1.5 (23) 0.58 0.0 (0) 0.0 (0) 0.00 0.0 (0)
Hypericum spp. L. (St. John's-wort species) 0.2 (3) 0.03 0.0 (0) 0.7 (4) 0.21 0.0 (0)
Ilex decidua Walt. (Possumhaw) 0.1 (1) 0.01 0.0 (0) 0.0 (0) 0.00 0.0 (0)
Ilex opaca Ait. (American Holly) 0.5 (7) 0.46 2.9 (6) 0.0 (0) 0.00 0.0 (0)
Ilex vomitoria Ait. (Yaupon) 12.3 (187) 21.26 13.5 (28) 3.7 (22) 4.81 3.2 (1)
Liquidambar styracifl ua L. (Sweetgum) 6.7 (101) 17.51 17.30 (36) 0.7 (4) 2.04 0.0 (0)
Myrica cerifera L. (Wax Myrtle) 5.2 (79) 1.75 1.0 (2) 0.0 (0) 0.00 0.0 (0)
Nyssa sylvatica Marsh. (Blackgum) 0.9 (14) 0.54 0.0 (0) 0.0 (0) 0.00 0.0 (0)
Parthenocissus quinquefolia (L.) Planch. (Virginia Creeper) 0.3 (4) 0.13 0.0 (0) 0.0 (0) 0.00 0.0 (0)
Persea borbonia (L.) Spreng. (Redbay) 0.7 (11) 1.58 3.4 (7) 0.0 (0) 0.00 0.0 (0)
Pinus echinata P. Mill. (Shortleaf Pine) 0.1 (1) 0.01 0.0 (0) 0.3 (2) 0.08 0.0 (0)
Pinus palustris P. Mill. (Longleaf Pine) 0.3 (5) 0.10 0.0 (0) 0.2 (1) 0.08 0.0 (0)
Prunus serotina Ehrh. (Black Cherry) 0.1 (2) 0.03 0.0 (0) 0.0 (0) 0.00 0.0 (0)
2009 R.R. Schaefer, R.R. Fleet, D.C. Rudolph, and N.E. Koerth 71
Table 3, continued.
High shrub-density plotB Low shrub-density plot
% of total % (# anole % of total % (# anole
Shrub speciesA % (# of plants) volume observations)C % (# of plants) volume observations)C
Prunus spp. L. (non-P. serotina plum species) 0.1 (1) 0.10 0.0 (0) 0.0 (0) 0.00 0.0 (0)
Quercus alba L. (White Oak) 1.9 (29) 2.89 3.9 (8) 0.00 0.0(0) 0.0 (0)
Quercus falcata Michx. (Southern Red Oak) 4.4 (66) 2.69 2.9 (6) 8.2 (49) 6.22 3.2 (1)
Quercus hemisphaerica Bartr. ex Willd. (Darlington Oak) 0.5 (7) 0.10 0.0 (0) 1.7 (10) 2.15 3.2 (1)
Quercus incana Bartr. (Bluejack Oak) 2.1 (32) 0.65 0.5 (1) 21.1 (126) 8.88 6.5 (2)
Quercus marilandica Muenchh. (Blackjack Oak) 4.6 (69) 1.34 4.3 (9) 0.0 (0) 0.00 0.0 (0)
Quercus nigra L. (Water Oak) 1.7 (26) 0.35 0.0 (0) 0.0 (0) 0.00 0.0 (0)
Quercus phellos L. (Willow Oak) 0.1 (2) 0.07 0.0 (0) 0.0 (0) 0.00 0.0 (0)
Quercus stellata Wangenh. (Post Oak) 3.1 (47) 1.98 1.0 (2) 0.0 (0) 0.00 0.0 (0)
Quercus spp. L. (oak species) 0.20 (3) 0.02 0.0 (0) 0.0 (0) 0.00 0.0 (0)
Rhus copallina L. (Shining Sumac) 0.6 (9) 0.22 0.5 (1) 45.3 (271) 15.54 3.2 (1)
Rubus spp. L. (blackberry species) 2.0 (30) 0.20 0.5 (1) 0.0 (0) 0.00 0.0 (0)
Sassafras albidum (Nutt.) Nees (Sassafras) 16.0 (242) 2.55 1.0 (2) 2.3 (14) 0.30 0.0 (0)
Smilax spp. L. (greenbrier species) 0.3 (5) 0.14 0.0 (0) 0.0 (0) 0.00 0.0 (0)
Vaccinium spp. L. (blueberry species) 11.6 (176) 3.08 4.3 (9) 0.0 (0) 0.00 0.0 (0)
Viburnum rufidulum Raf. (Rusty Blackhaw) 0.1 (2) 0.02 0.0 (0) 0.0 (0) 0.00 0.0 (0)
Vitis aestivalis Michx. (Summer Grape) 1.7 (26) 1.02 1.0 (2) 6.9 (41) 24.01 32.3 (10)
Vitis rotundifolia Michx. (Muscadine Grape) 0.4 (6) 11.93 5.8 (12) 0.0 (0) 0.00 0.0 (0)
Total observations 100.0 (1517) 100.00 100.0 (208) 100.0 (598) 100.00 100.0 (31)
AShrub = woody vegetation (including vines) ≥0.5 m and <3.0 m in height.
BLate spring and late summer Green Anole observations are combined.
CIncludes observations of Green Anoles that escaped capture.
72 Southeastern Naturalist Vol. 8, Special Issue 2
both late spring and late summer (Table 5). On both the high- and low-density
plots, most available shrubs (76.3% and 86.3%, respectively) were <1.0 m3.
On the high-density plot, only 81 (5.3%) and 47 (3.1%) of 1517 available
shrubs had a volume ≥4.0 m3 and ≥6.0 m3, respectively. In late spring, 31%
(n = 39) of all Green Anole observations on live shrub-level vegetation were
on shrubs ≥4.0 m3. By late summer, 34.1% (n = 28) of all Green Anoles were
observed on live shrub-level plants ≥6.0 m3. At the low-density plot, only 24
(4.0%) of 598 available shrubs had a volume ≥4.0 m3. In late spring, 45%
(n = 14) of all Green Anoles were observed on live shrub-level vegetation
≥4.0 m3. The use of voluminous shrubs by Green Anoles was proportionally
greater than their availability at both plots.
Discussion
Green Anole population size was much higher at the plot with greater
shrub density. Live shrubs were by far the most commonly used perch
substrate in both plots. Visually displaying adult males regularly perched
on hardwood mid-story trunks in the high-density plot during late spring.
By late summer, the majority of Green Anoles were juveniles and hardwood
mid-story stems were rarely used. Most adults at the high-density
plot disappeared between late spring and late summer, possibly having
succumbed to mortality. We do not know if a similar reduction in adult
Table 4. Anolis carolinensis (Green Anole) population size estimates (N) derived from the program
CAPTURE for two study plots in eastern Texas.
Plot, season ModelA N SE 95% CI
High shrub-density plot, late spring Mt 211 39.4 155–314
High shrub-density plot, late summer Mo 160 28.5 120–236
Low shrub-density plotB, late spring Mo 13 6.0 9–39
APopulation models selected by the program CAPTURE to estimate Green Anole population
sizes: Mt = capture probabilities varied with time, Mo = capture probabilities were constant.
BNo data for late summer.
Table 5. Width, height, and volume of live, shrub-level vegetation available to and used by
Anolis carolinensis (Green Anole) at two study plots in eastern Texas.
High shrub-density plot Low shrub-density plotA
Used Used
Available Late spring Late summer Available Late spring
Shrub (n = 1517) (n = 126) (n = 82) (n = 598) (n = 31)
dimensionB Mean SE Mean SE Mean SE Mean SE Mean SE
Width (m) 0.76 0.01 1.41 0.09 1.80 0.19 0.68 0.02 1.52 0.12
Height (m) 0.93 0.01 1.44 0.05 1.56 0.07 0.71 0.01 1.23 0.09
Volume (m3) 1.08 0.09 4.16 0.56 6.63 1.15 0.65 0.06 3.94 0.73
ANo data for late summer.
BShrub = vegetation ≥0.5 m and <3 m in height.
2009 R.R. Schaefer, R.R. Fleet, D.C. Rudolph, and N.E. Koerth 73
numbers occurred at the plot with fewer shrubs since we did not visit that
plot during late summer.
Jenssen et al. (1998) showed that perch height increased with body size
during “the beginning of the post-reproductive period.” Our data support this
as adults perched at significantly greater heights than juveniles at our highdensity
plot during late summer. However, this difference was not observed
at the high-density plot during late spring, or at the low-density plot. Only
a few large juveniles, that may have hatched the previous year, were captured
at the high-density plot during late spring. Thus, the perch heights of
these larger juveniles may approach that of the smaller adults. Few juveniles
were captured at the low-density plot as well. In this case, they were nearer
to hatchling-sized and clearly young of the year, but our very low sample
size may have prevented a significant difference between adult and juvenile
perch heights.
Green Anoles were the most common prey item (30% of total prey) delivered
to Southeastern American Kestrel nestlings in eastern Texas (R.R.
Schaefer, unpubl. data) and are a seasonally important prey item elsewhere
within the subspecies’ range (Smallwood and Bird 2002). A study involving
the examination of fecal samples collected from snakes in our region found
Coluber constrictor L. (Racer) and Masticophis fl agellum Shaw (Coachwhip)
to prey heavily on various lizards (D.C. Rudolph, unpubl. data).
However, Green Anole remains were positively identified only from Racer
(n = 1) and Agkistrodon contortrix L. (Copperhead, n = 2) fecal samples.
Many lizard remains could not be identified to species (n = 34), making the
extent of Green Anole predation by snakes in our region difficult to determine.
Little information is available regarding Green Anole predation by
other taxa in eastern Texas. Additional species occurring at our study plots
that have been reported to prey on Green Anoles elsewhere within its range
include Melanerpes carolinus L. (Red-bellied Woodpecker) (Arndt 1995),
and Vireo fl avifrons Vieillot (Yellow-throated Vireo) and V. olivaceus L.
(Red-eyed Vireo) (Sykes et al. 2007). Eumeces laticeps Schneider (Broadheaded
Skink), another potential predator found at our study plots, killed and
consumed a Green Anole while in captivity (Neill 1940). Large predatory
arthropods such as certain spiders may also prey on Green Anoles (Corey
1988). We observed one instance of cannibalism of a Green Anole hatchling
during this study (R.R. Schaefer, pers. observ.). Other than the Southeastern
American Kestrel, we know of no available information regarding the extent
of Green Anole predation by these taxa in our region. It is not known if the
various modes of predatory behavior exhibited by these taxa have any infl uence
on Green Anole perch site selection.
We found no literature references addressing the question of Green
Anole preference or avoidance of particular plant species. Our analyses
revealed that very few shrub-level plant species were preferred or avoided
by anoles. Green Anoles at both plots were found on shrubs with a greater
average volume than that of available plants. Greater shrub volume is
74 Southeastern Naturalist Vol. 8, Special Issue 2
clearly an important feature to Green Anoles, and appears to have a greater
influence than shrub species on an individual’s choice of perch sites.
Shrubs of greater volume were relatively scarce at both plots, and their use
by Green Anoles was proportionally greater than their availability. Though
we cannot say if Green Anoles seek larger shrubs for the purpose of avoiding
certain predators, a potential benefit of occupying shrub-level plants
of greater volume may be a reduction in the conspicuousness of anoles
to avian predators. When a predatory bird does detect an anole, it seems
probable the bird would have more difficulty retrieving the lizard from the
interior of a larger shrub. Additionally, larger shrubs may provide a greater
selection of escape routes for Green Anoles confronted by a predator. Sites
with a higher volume of shrub-level vegetation provide a greater number of
perches and presumably more arthropod prey, which in turn should support
higher Green Anole populations.
Green Anoles are attracted to dense shrubbery in open areas (Dundee and
Rossman 1989), making the fire-maintained pine habitats at our study plots
ideal. The higher-density shrub plot did not contain a contiguous layer of
woody, shrub-level vegetation. It was a mosaic of shrubs (single plants and
clumped) and openings with herbaceous, woody, and bare/leaf litter ground
cover. This vegetative structure provides good quality foraging habitat for
the Southeastern American Kestrel, which requires an open understory
for maneuverability and visual prey location (Hoffman and Collopy 1988,
Smallwood and Bird 2002). The vegetative structure of our low-density
shrub plot differed in that hardwood mid-story trees were nearly absent and
shrub-level vegetation was much reduced. This created an even more open
pine stand that still provided kestrel foraging habitat, but anole numbers
were much reduced. A reduction in anoles may reduce foraging habitat quality
for kestrels. On the other hand, a contiguously dense shrub layer may
harbor more anoles but may also hinder kestrel maneuverability. Thus, some
intermediate shrub density may provide optimal kestrel foraging habitat with
regard to Green Anoles.
Our results suggest that Green Anole abundance varies in response
to the density of shrub-level vegetation, but additional research with an
expanded number of plots that exhibit a gradient of shrub densities would
strengthen our understanding of the relationships between Green Anoles
and shrub characteristics.
Acknowledgments
We thank Lance D. McBrayer, Matthew A. Kwiatkowski, and two anonymous
reviewers for constructive comments on earlier drafts of this manuscript. We also
thank Daniel Saenz, Robert J. Allen, and John N. Macey for their assistance with
mark-recapture fieldwork.
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