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

Table 4.6. Relative abundance (mean + SE; no./ha/hr) of herpetofauna detected during intensive surveys
along random transects (n = 7) surveyed in both spring (9 April – 8 May) and summer (18 – 31 July),
Saguaro National Park, Rincon Mountain District, 2001.
Spring (n = 7) Summer (n = 7) All seasons
Species Mean SE Mean SE Mean SE
Sonoran Desert toad 0.43 0.43 0.21 0.21
canyon treefrog 0.07 0.07 0.04 0.04
desert tortoise 0.05 0.05 0.02 0.02
western banded gecko 0.05 0.05 0.02 0.02
eastern collared lizard 0.07 0.07 0.04 0.04
greater earless lizard 0.14 0.10 0.14 0.14 0.14 0.08
Clark’s spiny lizard 1.24 0.33 1.93 0.70 1.58 0.39
common side-blotched lizard 0.14 0.07 0.14 0.09 0.14 0.05
ornate tree lizard 2.14 0.43 1.14 0.48 1.64 0.34
unknown whiptail 1.43 0.43 0.21 0.15 0.82 0.28
Sonoran spotted whiptail 0.48 0.16 0.50 0.29 0.49 0.16
Gila spotted whiptail 0.14 0.14 0.29 0.15 0.21 0.10
western whiptail 0.33 0.19 0.07 0.07 0.20 0.11
Madrean alligator lizard 0.10 0.06 0.05 0.03
coachwhip 0.07 0.07 0.04 0.04
Sonoran whipsnake 0.10 0.06 0.14 0.09 0.12 0.05
western patch-nosed snake 0.07 0.07 0.04 0.04
black-necked garter snake 0.10 0.06 0.14 0.14 0.12 0.08
western diamond-backed rattlesnake 0.07 0.07 0.04 0.04
black-tailed rattlesnake 0.07 0.07 0.04 0.04
tiger rattlesnake 0.07 0.07 0.04 0.04
western rattlesnake 0.05 0.05 0.02 0.02
all individuals 5.48 0.68 5.07 1.33 5.27 0.72
abundance of ornate tree lizards and all whiptail
lizards combined were roughly two times greater
in the spring (t 6 ≥ 1.91, P ≤ 0.53) (Table 4.6). The
desert tortoise, western banded gecko, Madrean
alligator lizard, and western rattlesnake were
detected only in spring, whereas the Sonoran
Desert toad, canyon treefrog, coachwhip, and
western diamond-backed, black-tailed, and tiger
rattlesnakes were detected only in summer (Table
4.6). Eastern collared lizards were not detected
in spring except in the high-elevation stratum
(Table 4.5). Some of these patterns may have
been the result of low sample size, because in the
cases of western rattlesnake and collared lizards,
the patterns that we observed are opposite to the
known natural history of each species.
Environmental factors that explained
patterns of species richness and relative
abundance varied (Table 4.7). Snake richness
increased with cover of grasses whereas lizard
richness decreased with increasing cover of
bare ground. Species richness of snakes and
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lizards increased with shrub cover above
2 m, though influence of shrub cover was
much greater for snakes; richness of lizards
decreased with tree cover between 0.5 and 2.0
m. Relative abundance (no./ha/hr) of all lizard
species combined declined with increasing
cover of bare ground. For all lizards excluding
whiptails, however, relative abundance decreased
as grass cover between 0.5 and 2.0 m above
ground increased, whereas for whiptails relative
abundance decreased as vegetation cover between
0.5 and 2.0 m of all plant types combined
increased. In contrast to patterns for all species
of lizards combined, relative abundance of
eastern fence lizards increased with increasing
cover of bare ground. Relative abundance of
the Sonoran spotted whiptail and Clark’s spiny
lizard was positively associated with forb cover
between 0 and 0.5 m above ground, whereas
relative abundance of ornate tree lizards was
positively associated with grass cover in the same
vegetation stratum. Relative abundance was not