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2007 SOUTHEASTERN NATURALIST 6(1):111–124
Spatial Ecology of the Coachwhip, Masticophis flagellum
(Squamata: Colubridae), in Eastern Texas
Richard W. Johnson1, Robert R. Fleet2, Michael B. Keck3,*,
and D. Craig Rudolph4
Abstract - We radio-tracked nine Masticophis flagellum (Coachwhips) to determine
home range, habitat use, and movements in eastern Texas from April to October
2000. Home ranges of Coachwhips contained more oak savanna macrohabitat than
early-successional pine plantation or forested seep, based on the availability of these
three macrohabitats in the study area. Likewise, within their individual home ranges,
Coachwhips used oak savanna more than the other two macrohabitats, based on
availability. An analysis of microhabitat use revealed that, relative to random sites
within their home range, Coachwhips were found at sites with fewer pine trees and
more herbaceous vegetation taller than 30 cm. Results of the two analyses,
macrohabitat and microhabitat, were consistent: oak savannas contained relatively
few pine trees but much herbaceous vegetation taller than 30 cm. Coachwhips made
frequent long-distance moves, which resulted in large home ranges. Core activity
areas, however, were small. These core activity areas were always within the oak
savanna macrohabitat. Long movements, large home ranges, and small core activity
areas likely were a result of the preferred oak savanna macrohabitat being patchily
distributed in the landscape.
Spatial ecology of snakes has been less studied than that of most other
vertebrates, probably because of the secretive nature of snakes (Reinert
1993). Masticophis flagellum (Shaw) (Coachwhip) is a widely-distributed
and common snake, yet little is known about its spatial ecology. Only one
modern study (Secor 1995) has investigated this species’ spatial ecology.
Moreover, Secor’s study site, in the Mojave Desert of California, was near
the western limit of the species’ distribution. We are unaware of any quantitative
studies of home range or habitat use of this species in the southeastern
We studied the Coachwhip in eastern Texas, where it is a relatively
common snake. The Coachwhip is a fast, active, diurnal predator, and is
considered a thermal specialist, maintaining its body temperature between
30 and 35 °C (Hammerson 1989, Jones and Whitford 1989, Secor 1995). In
their popular field guide, Conant and Collins (1991) noted that eastern
1Arkansas Game and Fish Commission, Hampton Research Center, 31 Halowell
Lane, Humphrey, AR 72073. 2Department of Mathematics and Statistics, Stephen F.
Austin State University, Nacogdoches, TX 75962. 3Department of Biology, Grayson
County College, 6101 Grayson Drive, Denison, TX 75020. 4US Forest Service,
Southern Research Station, 506 Hayter Street, Nacogdoches, TX 75965. *Corresponding
author - email@example.com.
112 Southeastern Naturalist Vol. 6, No. 1
Coachwhips are found in a wide variety of habitats, from dry sandy
flatwoods to creek valleys and swamps. The objectives of our study were to
describe habitat use, movements, and home range of the Coachwhip in
The study site, privately owned by a timber company and known as
“Tonkawa Sands,” is located in Nacogdoches County, approximately 25 km
north of Nacogdoches, TX. Soils at Tonkawa Sands are classified as sand or
fine sand (Dolezel 1980) and are part of the east–west trending Carrizo sands
that encompass approximately 20 km2 of the area. Topographic relief is
minimal with elevations ranging from 133 to 216 m above sea level.
Three macrohabitat types were identified on the study site. The first, oak
savanna, was an open-canopy woodland dominated by Quercus incana
Bartram (bluejack oak) and Q. stellata Wangenhein (post oak) on upland xeric
sandy sites with a dense ground layer of grasses, forbs, and woody vines. The
second macrohabitat type was early-successional pine plantations, consisting
of a mosaic of even-aged stands of Pinus taeda Linnaeus (loblolly pine). The
stands differed in age and height, but in all stands the trees were closelyspaced,
the canopy was nearly closed, a thick layer of pine needles existed on
the forest floor, and little ground-layer vegetation was present. The third
macrohabitat type was located at lower elevations and consisted of closedcanopy
mesic forested seeps dominated by Acer rubrum Linnaeus (red maple)
and Magnolia virginiana Linnaeus (sweetbay magnolia), with sphagnum
moss and various fern species as ground-layer vegetation.
The study site experienced drought conditions during the year of our
study. The previous ten-year (1989–1999) average rainfall from July to
October was 10.4 cm, almost 3.5 times more than during 2000 (3.0 cm;
Stephen F. Austin University Weather Station data).
Ten adult Coachwhips, seven males and three females, were captured on
the study site between 27 March and 21 June 2000 in drift-fence traps that
were placed in grids without regard to habitat type. Radiotransmitters (50 x
11 x 5 mm, with a 44-cm whip antenna) were implanted subcutaneously
following the procedures described by Reinert and Cundall (1982) and
Weatherhead and Anderka (1984). The mass of the transmitters (3.4–6.3 g)
was always less than 2% of snake mass (192–1030 g; snout-vent length:
104–152 cm). Snakes were held in the laboratory a minimum of seven days
post-surgery for recovery. Snakes were released at the original point of
capture and relocated three to four times per week from 18 April through 19
October; this period roughly coincides with the entire active season of
Coachwhips at the site (during 4 years of drift-fence sampling at the site, the
2007 R.W. Johnson, R.R. Fleet, M.B. Keck, and D.C. Rudolph 113
average first date of capture was 29 March and the average last capture date
was 30 September; D.C. Rudolph, unpubl. data).
Each time a snake was relocated, the site coordinates were recorded
using a GPS unit (Trimble Geoexplorer II). Data points were differentially
post-processed for increased accuracy by correcting against a known location
base station (Kennedy 2002). We recorded which of the three
macrohabitat types was dominant at the snake’s location, and whether the
snake was below ground, on the soil surface, or above ground in vegetation.
Microhabitat characteristics of basal area (measured with a 1-factor metric
prism [m2/ha]), canopy closure, distance to nearest tree, and foliage density
of ground-layer vegetation (measured using a density board; MacArthur and
MacArthur 1961) were recorded. Additional characteristics of the microhabitat,
recorded in a 1-m radius circle around each snake location, included
proportional cover of leaf litter, bare ground, and herbaceous vegetation
greater than and less than 30 cm in height; these proportions always summed
to 1. Depth of leaf litter (average of four measurements) and the presence or
absence of a protective overhang (measured as dense herbaceous vegetation,
woody vegetation, or woody debris) available for snake concealment also
The same data recorded at snake locations were recorded at random
locations within each snake’s home range to determine if habitat use within the
home range was random, or if certain habitats were used in greater or lesser
proportion to their availability. One random location was sampled for each
snake relocation point. Random points were chosen by using random number
tables for selecting direction and distance from snake relocation points.
Following Aebischer et al. (1993), we considered habitat use at two
scales: (1) we tested whether habitat within the snakes’ home ranges was a
random subset of available habitat in the study area, and (2) we tested
whether habitat at snake locations was a random subset of available habitat
within the snakes’ home ranges.
We defined the study area as the portion of the study site enclosed by a
single minimum convex polygon (594 ha) bounded by the outermost relocation
points of all snakes. This circumscribed an area within which our snakes
were moving and potentially using sites from the available habitats. The
proportion of the study area and the proportion of each snake’s home range
composed of each of the three macrohabitat types was calculated using a
satellite image of the study area and the GIS program Arc View 3.1 (Environmental
Systems Research Institute, Redlands, CA). We analyzed these data
with compositional analysis (Aebischer and Robertson 1992, Aebischer et al.
1993) using the software package Resource Selection for Windows ver. 1.0.
To compare habitats at snake locations to available habitats within the
snakes' home ranges, we used compositional analysis for macro- and microhabitat
variables that were proportionally based wherein the proportions of
multiple categories summed to one (i.e., proportions of the three
114 Southeastern Naturalist Vol. 6, No. 1
macrohabitat types: oak savanna, pine plantation, forested seep; proportional
microhabitat data collected within a 1-m radius of snake and random
points: proportion dominated by leaf litter, bare ground, vegetation greater
than 30 cm in height, or vegetation less than 30 cm). Unlike traditional
methods of analysis (i.e., conventional analysis of variance [ANOVA]/
multiple analysis of variance [MANOVA]), compositional analysis is appropriate
for analyzing these types of non-independent proportions (Aebischer
et al. 1993).
Other microhabitat data (i.e., canopy closure, density of ground-layer
vegetation, basal area of pine and hardwood trees, distance to nearest tree,
leaf-litter depth, and presence of a protective overhang) were analyzed using
9 x 2 two-way mixed-model ANOVAs with no replication (one data point
per snake to avoid pseudoreplication; Aebischer et al. 1993, Hurlbert 1984),
with individual snake being a random factor (nine snakes), snake/random
points being a fixed factor, and the average value for the microhabitat
characteristic being the dependent variable. Analysis of variance procedures
followed Sokal and Rohlf (1995) using the STATISTICA 5.1 software
package (Statsoft Inc, Tulsa, OK).
A movement was defined as the location of a snake at a site farther than 5
m from its previous relocation point. Movement frequency was calculated as
the number of movements divided by the number of relocations (Charland
and Gregory 1995). Because individuals were not relocated every day,
average movement rates were calculated by two different methods as described
by Charland and Gregory (1995). Overall movement rate (OMR)
was calculated by dividing the total distance moved by the total number of
days in the analysis period. Actual movement rate (AMR) was calculated by
dividing total distance moved by the number of relocations in which a
movement was detected. Since AMR excluded days when a snake did not
move, the value of AMR was always greater than OMR.
Three different methods were used to analyze Coachwhip home range
using the computer program CALHOME (Kie et al. 1996). Because of their
widespread use in other studies, the minimum convex polygon (MCP) and
the harmonic mean (HM) methods were used as a basis of comparison. We
also used the adaptive kernel method (ADK) because Worton (1987, 1995)
suggested that this method was superior to the HM method. Since the
statistically-based HM and ADK methods allow the computation of core
activity areas, we calculated the 50% core activity areas of each snake using
both of these methods.
One female snake lost significant mass (47%) during the tracking period.
Because animals may not behave normally when sick or when deprived of
food and water (Bernheim and Kluger 1976, Dunlap 1995, Kluger 1978), data
obtained from this individual were not used in analyses due to possible bias.
Of the remaining nine snakes, four were tracked until the end of the study (19
October), four died from unknown causes, presumably predation, and the
transmitter signal was lost from one. To determine if the snakes were healthy,
2007 R.W. Johnson, R.R. Fleet, M.B. Keck, and D.C. Rudolph 115
we recaptured and briefly examined each of them at least once during the
study. Additionally, all remaining snakes were recaptured at the end of the
study, and the radiotransmitter was removed from each of them. All nine
snakes appeared healthy when checked, and there were no noticeable complications
from the surgical implantation of the radiotransmitters. We tracked
these nine snakes an average of 106 days each (SD = 32.4, range = 75–184 d),
and we recorded a total of 336 locations (range = 24–62 per snake).
All relocation points, from time of release until 19 October, were used in
computing home ranges; however, habitat and movement data collected
prior to 14 days post-release were omitted from all analyses to decrease the
chance of bias due to the effects of surgery or re-acclimatization to the
natural environment (Peterson et al. 1993, Rudolph et al. 1998). To avoid
biases associated with seasonal differences in movement rates, movement
data were analyzed only between 7 July and 10 September, the longest
consecutive time period when the greatest number (seven) of snakes were
monitored. For the habitat-use data, we analyzed data collected over the
entire study period, and then we re-analyzed those data collected between 7
July and 10 September; however, because of the high degree of congruence
between these two analyses, we only present details of the analysis of the
complete data set.
The study area was composed of 16% forested seep, 34% oak savanna and
50% pine plantation. The average snake MCP home range was composed of
5% (SD = ± 9.7%) forested seep, 57% (± 15.0) oak savanna, and 38% (± 9.7)
pine plantation. Compositional analysis revealed that macrohabitat proportions
within the snakes’ MCP home ranges differed significantly from the
macrohabitat proportions available on the study area ( = 0.209, P < 0.001;
Fig. 1). Pairwise comparisons of macrohabitat types indicated that home
ranges included significantly more oak savanna than pine plantation (t = 4.13,
df = 8, P = 0.0033; see Aebischer et al.  for a justification of using
standard significance levels of t-tests for comparisons following a significant
-value in compositional analysis) and forested seep (t = 4.13, df = 8, P =
0.0033) based on proportions available in the study area (Fig. 1). Furthermore,
snake home ranges contained significantly more pine plantation than forested
seep macrohabitat (t = 3.22, df = 8, P = 0.0123; Fig. 1).
Because home ranges may contain large portions of unused habitat,
further analysis was conducted to determine if snakes were disproportionately
using certain macrohabitat types within their home range. Coachwhips
were more often located within oak savanna habitats (mean = 91 ± 5.3%; n =
9 snakes) than pine plantations (8 ± 5.9%) and forested seeps (1 ± 1.5%).
Compositional analysis revealed that snakes used macrohabitats significantly
differently than available within their home ranges ( = 0.243, P <
0.05; Fig. 1). Pairwise comparisons indicated that within their home ranges,
116 Southeastern Naturalist Vol. 6, No. 1
Coachwhips used oak savannas disproportionately more than pine plantations
(t = 4.70, df = 8, P = 0.0015) and forested seeps (t = 2.36, df = 8, P =
0.0457; Fig. 1). No significant difference was detected between pine plantations
and forested seeps (t = 1.13, df = 8, P = 0.29).
To determine if snakes disproportionately used certain microhabitat features,
based on availability within their home ranges, random points within
each individual’s home range were compared to snake locations. Of all
microhabitat variables, only pine basal area and the presence of a protective
overhang were significant (Table 1). Pine basal area, analyzed using a two-way
ANOVA, was significantly lower at snake locations than at random points (P =
Table 1. Mean ± standard deviation for microhabitat variables at Coachwhip locations and
random points within Coachwhip home ranges. The last column represents the results of twoway
mixed-model ANOVAs comparing the snake locations to random points (see Methods:
Data analysis). A significant difference was defined as P < 0.05 and is designated by an asterisk.
Snake locations Random points P
Canopy closure (%) 45.6 ± 6.7 43.8 ± 5.9 0.602
Foliage density (m) 11.6 ± 3.5 11.3 ± 1.9 0.857
Basal area pine (m2/ha) 3.1 ± 1.5 6.2 ± 2.3 0.004*
Basal area hardwood (m2/ha) 4.5 ± 1.4 4.4 ± 2.6 0.897
Distance to tree (m) 3.7 ± 1.3 4.2 ± 2.1 0.244
Litter depth (cm) 1.5 ± 0.6 2.0 ± 0.7 0.058
Protective overhang (%) 68.8 ± 0.2 21.9 ± 0.2 0.001*
Figure 1. Percentage of the study area, coachwhip MCP home range, and coachwhip
location points within each of three macrohabitat types. Above each bar is the mean ±
SD. Macrohabitat use at two scales is demonstrated: (1) available habitat in the study
area compared to habitat in snake home ranges, and (2) available habitat in snake
home ranges compared to snake location points. At both scales, oak savanna was
used more than the other two macrohabitats, based on availability.
2007 R.W. Johnson, R.R. Fleet, M.B. Keck, and D.C. Rudolph 117
0.004). These results support the findings of the macrohabitat analysis wherein
Coachwhips avoided areas of pine plantations. The presence of a protective
overhang, variously composed of woody debris, grass, or forbs, was found
more often at snake locations than at random points (P = 0.001; Table 1).
Proportion of four categories of ground cover (bareground, leaf litter,
herbaceous vegetation < 30 cm, herbaceous vegetation > 30 cm) was analyzed
using compositional analysis (Table 2). The analysis indicated these microhabitat
features were not used in proportion to their availability ( = 0.253, P <
0.05). Pairwise comparisons indicated that snake locations had significantly
more herbaceous vegetation greater than 30 cm in height than both bare ground
(t = 3.41, df = 8, P = 0.0093) and herbaceous vegetation less than 30 cm in
height (t = 2.66, df = 8, P = 0.0287). Snake locations also contained more
herbaceous vegetation greater than 30 cm in height than leaf litter, but the
difference was not quite statistically significant (t = 2.21, df = 8, P = 0.0578).
Snakes had returned to previously used refugia, often small mammal
burrows, on 19% of telemetry relocations (range of individuals: 0–30%,
n = 9). Individuals also used refugia previously used by other individuals,
but no two radio-tracked individuals occupied the same refuge at the same
time. Individuals were surface active on the ground 28% of the time, arboreal
11% of the time, and in underground refugia 61% of the time.
The results of the macro and microhabitat analyses restricted to the late
summer period, 7 July–10 September, were congruent with the analyses of
the complete active season with one minor exception: in the microhabitat
analysis, herbaceous vegetation greater than 30 cm tall was used significantly
more than leaf-litter microhabitats in the late summer (t = 3.00, df = 6,
P = 0.024), but this result was not quite statistically significant in the
analysis of the complete active season (P = 0.0578; see above).
Movements and home ranges
We detected no significant difference in home-range size between males
and females (MCP: t = 0.87, df = 7, P > 0.41; all data April–Oct included),
and we detected no significant intersexual difference in the actual movement
rate (AMR) of males and females tracked between 7 July and 10 September
Table 2. Mean ± standard deviation of four categories of ground cover at snake locations and
random points within snake home ranges. The columns sum to 100%. Compositional analysis
indicated that these microhabitat features were not used in proportion to their availability ( =
0.253, P < 0.05). A significant difference (as determined by pairwise t-tests) in usage by
coachwhips is indicated by cells in the second column not having at least one superscript in
common; thus, coachwhip locations contained more herbaceous vegetation greater than 30 cm
tall than bare ground or herbaceous vegetation less than 30 cm tall, based on the availability of
Snake locations Random points
Bare ground 9 ± 6.3%A 14 ± 9.9%
Leaf litter 39 ± 13.9%AB 43 ± 12.9%
Vegetation < 30 cm tall 9 ± 7.0%A 14 ± 3.5%
Vegetation > 30 cm tall 43 ± 13.3%B 29 ± 8.9%
118 Southeastern Naturalist Vol. 6, No. 1
(t = 0.58, df = 5, P > 0.58). One of the two females tracked between 7 July
and 10 September oviposited 12 eggs in the laboratory on 22 June, before
transmitter implantation. Both of these females were palpated and known to
be non-gravid in early July. Consequently, both must have been non-gravid
through the end of the study (oviposition dates for Coachwhips are typically
in June or early July [Fitch 1970, Wright and Wright 1994]). Therefore, we
pooled the data from both sexes for summary statistics.
Coachwhips moved frequently and for long distances (Table 3). They
occupied large home ranges but small core areas (50%) of activity (Table 4;
Fig. 2). Two snakes with exceptionally large MCP home ranges (142.1 and
268.4 ha) strongly influenced the mean home-range size (MCP = 70.4 ± 83.8
ha). However, mean home range calculated without these two individuals
was still large (MCP = 31.9 ha). The 50% core activity area estimates were
2.2 ha (HM) and 13.6 ha (ADK), both less than 11% of the total home range
(100%) calculated by those methods. There was broad overlap among the
home ranges of different snakes (Fig. 3). Home-range size (MCP) was not
significantly correlated with body mass (r = -0.22, n = 7, P = 0.63) or with
snout vent length (r = -0.15, n = 7, P = 0.76).
During the active season (April–October) at our study site, Coachwhips
used oak savanna more frequently than expected based on its availability on the
study area and within the snake home ranges (Fig. 4). These oak savannas are
found on xeric sandy upland sites and have a dense ground layer of grass and
other herbaceous vegetation within an open canopy forest of bluejack oak and
post oak. The disproportionate use of this macrohabitat could be due to several
factors including thermoregulatio, prey availability, and predator avoidance.
Coachwhips are known to be thermal specialists (Hammerson 1989,
Jones and Whitford 1989, Secor 1995) and oak savanna macrohabitat may
provide conditions allowing them to effectively thermoregulate. These
Table 4. Home ranges of nine Coachwhips (in hectares). MCP = minimum convex polygon; HM
= harmonic mean; ADK = adaptive kernel. All 336 data points (24–62 per snake) gathered
April–October were included in these calculations.
MCP 100% HM 100% ADK 100% HM 95% ADK 95% HM 50% ADK 50%
Mean 70.4 64.6 133.1 38.3 84.9 2.2 13.6
Range 16.1–268.4 19.4–227.4 35.9–470.4 14.2–142.3 17.0–328.3 0.3–5.7 0.6–68.8
Table 3. Mean and range of movements (in meters) for seven Coachwhips tracked from 7 July to
10 September. Movement frequency, minimum (Min), and maximum (Max) movement distance
(in meters) also are listed. See Methods for definition of overall movement rate (OMR)
and actual movement rate (AMR).
OMR AMR Frequency Min Max
Mean 73 93 78% 37 653
Range 53–133 70–177 50–95% 6–96 302–1084
2007 R.W. Johnson, R.R. Fleet, M.B. Keck, and D.C. Rudolph 119
conditions are most likely provided by the absence of a well-developed
canopy, which permits sunlight to penetrate to the surface, yielding a mosaic
of substrate temperatures (Swaim and McGinnis 1992). Our microhabitat
Figure 3. 100% MCP
home ranges of nine
Coachwhips. The home
ranges of the snakes
Figure 2. Example
of a Coachwhip
home range. Although
home range was
large (56.2 ha), the
50% adaptive kernel
(ADK) core areas
smaller (total area =
8.9 ha) and always
located in oak savanna
Some snake location
locations for this
120 Southeastern Naturalist Vol. 6, No. 1
analysis, which indicated that Coachwhips did not disproportionately use
open-canopy sites (Table 1), might appear inconsistent with the hypothesis
that Coachwhips select sites with open canopies. However, we stress that our
microhabitat analyses, unlike our macrohabitat analyses, compared snake
locations to random locations within snake home ranges. The home ranges
of the Coachwhips, which were dominated by open-canopy oak savanna,
were not representative of the study site as a whole.
The oak savanna environment used by Coachwhips in eastern Texas may
be important for thermoregulation, but it also likely provides a habitat of
high prey density. We observed no feeding by Coachwhips, but scat analysis
of Coachwhips trapped from this study site revealed a diet dominated numerically
by lizards (Sceloporus, Aspidoscelis, and scincids), orthopterans
and other insects, and small rodents (D.C. Rudolph, unpubl. data); the
density of these prey species likely increases with increasing amounts of
ground-cover vegetation (Collins et al. 2002, Parajulee et al. 1997, Thill et
al. 2004, Windberg 1998). Ground-cover vegetation was most abundant in
the oak savanna macrohabitat.
The ground-cover vegetation of oak savannas also may be important for
protection from predators. Active species incur higher risks because movement
can attract predators (Plummer and Congdon 1994, Plummer and Mills 2000,
Figure 4. Telemetry locations
filled circles) of nine
Coachwhips (336 relocation
on the study area. Relocations
snakes were clustered
in the oak savanna
2007 R.W. Johnson, R.R. Fleet, M.B. Keck, and D.C. Rudolph 121
Secor 1995). We observed no direct predation on Coachwhips, but potential
predators that were common at the study site included Buteo jamaicensis
(Gmelin) (Red-tailed Hawks), Buteo lineatus (Gmelin) (Red-shouldered
Hawks), Canis latrans Say (coyotes), and Procyon lotor (Linnaeus) (raccoons).
Coachwhips in eastern Texas used microhabitats that offered great
concealment. In the open-canopy oak savanna, Coachwhips often were found
in dense herbaceous vegetation which provided protective overhead concealment;
snakes used these microhabitat sites in greater proportion than their
availability within their home ranges.
As further evidence of the importance of concealing vegetation for
predator avoidance, our experience in relocating these snakes indicated that
when sensing our presence they would climb trees, descend mammal burrows,
or hide beneath other concealing objects. In retreating to these refugia,
the snakes did not take the most direct route, rather they took routes through
ground cover that offered the greatest concealment.
Coachwhips in eastern Texas exhibited a pattern of frequent, long-distance
moves, sometimes exceeding a straight-line distance of 1 km in a 24-hour
period. Secor (1995) found that Coachwhips in the Mojave Desert did not move
in a straight line, but rather moved in a meandering fashion that resulted in a
total distance moved of 1.4 times the straight-line distance. Thus, for comparison,
the AMR of eastern Texas Coachwhips was recalculated using Secor’s
meander ratio of 1.4. Using the meander ratio, our estimate of the movement
rate of eastern Texas Coachwhips approached those observed in the Mojave
Desert (eastern Texas: 134 m/day; Mojave Desert: 186 m/day).
Mating presumably occurs primarily in May at our study area. We base
this presumption on the peak in multiple Coachwhip captures, generally
consisting of an adult female and one or more adult males, in funnel traps
during this period (D.C. Rudolph, unpubl. data). A mating season in April or
May would be generally consistent with observations of mating and oviposition
reported by others (Fitch 1970, Werler and Dixon 2000, Wright and
Wright 1994). Since most of our data were collected after May, we do not
believe that the frequent long-distance moves exhibited by Coachwhips
were a result of reproductive behavior. Thus, the abundance and distribution
of prey may have been the primary factor governing movement of snakes in
our study. If prey is frequently encountered in the habitat, movements may
be short, but if prey is widely dispersed and patchily distributed, frequent
and/or long-distance movements between prey patches may be necessary
(Gregory et al. 1987, King and Duvall 1990, Macartney et al. 1988, Shine
and Fitzgerald 1996, Whitaker and Shine 2003).
The high degree of movement activity resulted in a very large average
home range, one of the largest home ranges of any snake that has been
studied (Macartney et al. 1988, Secor 1995). However, comparisons of
home-range size across studies/species are complicated by differing methodologies,
quality of data, and by habitat variability (Gregory et al. 1987,
Macartney et al. 1988). Additionally, so few snake species have been studied
that attempts to form general conclusions concerning the home-range size of
particular taxonomic or ecological groups are further complicated.
122 Southeastern Naturalist Vol. 6, No. 1
Despite dissimilar habitats, Coachwhips in eastern Texas and in the
Mojave Desert had similar home ranges; the observed 100% MCP was
somewhat larger in eastern Texas (70.4 ha in eastern Texas versus 57.9 ha in
the Mojave Desert [Secor 1995]), but the observed 95% HM was somewhat
smaller in eastern Texas. (38.3 ha versus 53.4 ha).
Home-range size was large for eastern Texas Coachwhips using three
different estimators (Table 4). However, these home ranges contained large
areas of unused or underused habitat (Fig. 2). Within their home ranges,
Coachwhips used the patchily-distributed oak savanna macrohabitat more
than expected based on its availability; hence, they underused early-successional
pine plantations and forested seeps. The Coachwhips’ high degree of
movement activity, wherein individuals returned to previously occupied
patches of oak savanna and repeatedly returned to previously used refugia
(mean = 19%), indicates a high degree of familiarity with their environment.
Frequent repeated use of the same oak savanna patches resulted in relatively
small 50% core activity areas (Table 4). These core activity areas were, in all
cases, areas of preferred oak savanna macrohabitat that were patchily distributed
within the snakes’ home ranges. These areas must have provided resources
essential to the Coachwhips, which may explain the high degree of overlap
among different snakes’ home ranges; individuals often were found in close
proximity to one another and at times used the same refugia (but not simultaneously).
The essential resources at these sites were most likely an abundance
of prey, which is required for this species to support its high energetic needs
(Ruben 1977, Secor and Nagy 1994), and open habitat necessary for optimal
thermoregulation. The patchy availability of resources (suitable macrohabitat,
optimal refugia, prey) may best explain the frequent long-distance movements,
large 100% home ranges with small 50% core activity areas, and repeated use
of underground refugia within the home ranges.
In summary, at the landscape level, Coachwhips were found in dry sandy
uplands. At the macrohabitat level, they were found in oak savannas, and at the
microhabitat level, they were found in tall herbaceous vegetation, frequently
under protective overhangs or in burrows. Although Coachwhips moved
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structurally similar but taxonomically different habitats, such as Pinus
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Coachwhips in the southeastern United States.
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