||The Mammals of Texas -
Mexican Spiny Pocket Mouse
Rodentia : Family Heteromyidae
: Liomys irroratus (Gray)
Description. A medium-sized mouse with
extremely harsh pelage over entire upperparts (the hairs
flattened, sharp-pointed and grooved); external, furlined
cheek pouches; and relatively long tail. Similar in
general appearance to the spiny-haired pocket mice (Chaetodipus), but upper incisors lack
the longitudinal groove on the outer face and the pelage
is much more spiny and harsh. Tail about as long as head
and body, sparsely haired and distinctly bicolor,
brownish above, whitish below; upperparts dark gray,
grizzled with orange; underparts pure white; sole of
proximal half of hind foot hairy, blackish. External
measurements average: total length, 237 mm; tail, 122 mm;
hind foot, 30 mm. Weight: males, 50-60 g; females, 35-50
g. Dental formula as in Perognathus flavescens.
Distribution in Texas. A Mexican form
reaching the United States in extreme South Texas.
Habits. In southern Texas they
live in the densest brush on the ridges forming the old
banks of the Rio Grande, along oxbows, and in the
scattered remnants of the subtropical palm forests of the
Rio Grande near Brownsville (Cameron County). They are
often closely associated with thickets of prickly pear.
In northern Mexico, they may be trapped among dense
chaparral but in the valley of Mexico they occurred
around stone fences and among rocks on the sides of
mountain slopes. They live in burrows and sometimes throw
up small mounds to close the entrances. Usually the
openings are covered by vegetation or dead leaves. They
are strictly nocturnal.
In southern Texas, they feed on the
seeds of hackberry, mesquite, and various other shrubs.
In addition, seeds of various weeds may be found in their
Very little is known about their
breeding habits. In Mexico, half-grown young have been
found in June and nearly full-grown young in August. None
of the females captured in summer was pregnant or
lactating. Based on the study of a large number of
Mexican records, Theodore Fleming reported immature
individuals of Liomys irroratus from all months
except May; he believed that breeding occurs throughout
the year but with most of it concentrated in the winter
period from November to February. Litter size is two to
eight, averaging about four.
Photo credit: John L. Tveten.