Vascular Plant and Vertebrate Inventory of Saguaro ... - USGS

Table 4.9. Relative abundance (no./hr) of herpetofauna detected during road surveys,
Saguaro National Park, Rincon Mountain District, 2001 and 2002.
Species mean SE
Couch’s spadefoot toad 1.74 1.38
Sonoran desert toad 5.74 1.52
red-spotted toad 6.04 1.64
Great Plains toad 0.06 0.06
western banded gecko 0.64 0.19
greater earless lizard 0.09 0.05
desert spiny lizard 1.85 0.80
common side-blotched lizard 0.02 0.02
ornate tree lizard 0.06 0.04
regal horned lizard 0.15 0.05
western whiptail 0.05 0.05
Gila monster 0.15 0.08
coachwhip 0.04 0.03
western patch-nosed snake 0.01 0.01
long-nosed snake 0.14 0.06
night snake 0.10 0.04
western diamond-backed rattlesnake 0.25 0.14
black-tailed rattlesnake 0.01 0.01
tiger rattlesnake 0.29 0.19
all individuals 17.48 2.72
with temperature (t 77 = 0.05, P = 0.95). Relative
abundance of snakes increased with temperature
(estimate = 0.5/Cº, SE = 0.2, t 79 = 2.34, P =
0.022) and did not vary with relative humidity
or cloud cover (t 79 ≤ 0.77, P ≥ 0.45). Further,
species richness decreased with increasing
cloud cover for lizards (t 77 = 4.92, P < 0.0001)
and increased with increasing cloud cover for
amphibians (t 77 = 2.10, P = 0.039) after adjusting
for the influence of survey time and elevation.
Most surveys were in the low-elevation
stratum (58.8%) with fewer in the middle-
(27.1%) and high- (14.1%) elevation strata.
Relative abundance during daytime surveys
varied among strata (F 2, 51 = 12.9, P < 0.0001,
ANOVA) and was 2-times lower in the middle-
and 4.2-times lower in high-elevation strata than
in the low-elevation stratum (79.9 ± 8.3; Table
4.7). Species richness for daytime surveys also
varied with elevation (F 2, 51 = 18.3, P < 0.0001,
ANOVA) and was 1.7 times lower in the middle-
and 2.5 times lower in the high-elevation strata
than in the low-elevation stratum (7.3 ± 0.5).
Patterns of species occurrence and
relative abundance often varied across elevation.
We detected 17 species in only the low-elevation
stratum whereas we detected a single species,
the greater short-horned lizard, in only the
38
high-elevation stratum (Table 4.8). Relative
abundance increased with elevation for eight
species (Sonoran spotted and western whiptail,
Clark’s spiny lizard, zebra-tailed lizard, ornate
tree lizard, greater earless lizard, common sideblotched
lizard, and western diamond-backed
rattlesnake) and decreased with elevation for two
species (Madrean alligator lizard and eastern
fence lizard) (P ≤ 0.061, test of slope from
regression) after adjusting for other important
factors such as time of day and temperature.
Canyon treefrogs were most common in the
middle-elevation stratum (t 82 = 2.15, P = 0.034,
test of quadratic term from regression).
Relative abundance of many species was
too low or distribution too restricted to facilitate
quantitative comparisons of species occurrence
and relative abundance. Only a single Great
Plains skink (along lower Chimenea Canyon) and
lesser earless lizard (along lower Rincon Creek)
were detected. Only one western patch-nosed
snake (in a rocky canyon dominated by Sonoran
desertscrub) and one mountain patch-nosed
snake (in open pine-oak woodland at ≈1,770 m)
were detected. Similarly only one Sonoran coral
snake (in Sonoran desertscrub) and one common
kingsnake (lower Rincon Creek) were detected.
All 100 lowland leopard frogs that we observed