Phrynosoma
platyrhinos
(Desert Horned Lizard)
|
Key Characteristics |
Long horns (longer than they are wide at the base) |
Oviparous (egg laying) |
General
Description:
Desert Horned
Lizards are variable in color, and their color scheme often matches the surrounding
soil (Stebbins 1985). The coloration varies from gray, tan, or reddish-brown
ground colors, with wavy dark blotches arranged in two rows (one on either
side), (Storm and Leonard 1995). Two dark blotches on the neck are very
prominent and are bordered posteriorly by a light white or gray color.
The light border also penetrates in between the two neck blotches. Blotches
that are similarly shaded (dark then a light border posteriorly) are also
found on the tail, and they tend to form a banded appearance. The ventral
coloration is generally white, and often speckled with dark spots.
Desert Horned Lizards have horns that are longer than they are wide at the base (which isn't true for their congener, the Short-horned Lizard), (Nussbaum et al. 1983). Another difference between the two species is that the head tapers much less on Desert Horned Lizards, giving them a very blunt-nosed appearance (their specific epithet "platyrhinos" translates as "flat nose"). In addition to the horns on their head, Desert Horned Lizards also have many small horn-like scales on their dorsal surface, and these scales form a single row that fringes the sides of these lizards.
Desert Horned Lizards are larger than Short-horned Lizards, and are capable of attaining sizes of about 95 mm snout-vent length (3.75 in.) and 140 mm (5.5 in.) total length (Storm and Leonard 1995). Although different in size, Desert Horned Lizards are similar to Short-horned Lizards in that both species prey primarily on ants. In fact, horned lizards can often be found in the vicinity of ant hills, where they sit and wait for ants to pass by (Nussbaum et al. 1983).
Although hard to determine in the field, another key difference between the two species of horned lizards found in Idaho is that Desert Horned Lizards are oviparous (egg laying). These lizards mate in the spring and lay 2-16 eggs in June, which hatch some time in August (Nussbaum et al. 1983). The young resemble the adults both in shape and in coloration.
Habitat:
Desert Horned
Lizards are found in arid regions that have at least some loose soil available
for burrowing. I generally find this species in areas with sandy
soils and limited vegetation such as sagebrush or shadscale. However,
they can also be found in areas with hardpan and gravelly
soils as well (Behler and King 1979), (Nussbaum et al. 1983), (Stebbins
1985). Desert Horned Lizards are less cold adapted and are found at
lower elevations than the Short-horned Lizard (Storm and Leonard 1995).
Idaho
Distribution:
In Idaho, Desert
Horned Lizards are restricted to the southwestern portion of the state. From
southeastern Oregon, southwestern Idaho, and northern Utah, south through
southwestern U.S. desert to northern Mexico.
Diet:
Generally an ant specialist, but also
eats other slow, terrestrial insects such as beetles. May also eat spiders
and some plant material.
Ecology:
Hibernates
/aestivates.
Duration of seasonal inactive period varies with local climate. Emerges usually
in March in southern Nevada, with little evident adult activity after mid-July.
In southern range, may be active on warm nights; in north, generally inactive
and buried in soil at night. Nevada study reported population density of 5/ha.
Predators include Prairie Falcons, Loggerhead Shrikes, longnose leopard lizards,
and striped whipsnakes.
Reproduction:
Mating occurs from April to June.
Eggs are laid from April to July (apparently, mainly early June) in southern
Nevada; clutch size averages about 7 eggs. Female produces 1-2 clutches/yr.
Incubation lasts about 50-60 days. Individuals reach maturity in about 22
mo.
Conservation:
|
Status: |
Unprotected nongame species |
|
Global Rank |
G5 |
|
State Rank |
S4 |
Important State References:
Diller, L.V. and D.R.
Johnson. 1982. Ecology of reptiles in the Snake River Birds of Prey Area.
USDI Bur. Land Manage. Snake River Birds of Prey Research Project, Boise.
107pp.