||The Mammals of Texas -
Mearns' Grasshopper Mouse
Rodentia : Family Muridae : Onychomys
Description. A small,
"fat-tailed" mouse with pinkish-cinnamon or
grayish-buff upperparts and pure white underparts;
usually a conspicuous white or grayish tuft at anterior
base of ear; nose, cheeks and sides white; tail sparsely
haired, more than 30% of total length, from two to 21/2
times as long as hind foot and distinctly bicolor, dark
above and white below. Similar to Onychomys
leucogaster, but smaller,
with relatively longer tail, and smaller teeth. Juveniles
similar to adults, but upperparts bluish gray. External
measurements average: total length, 146 mm; tail, 52 mm;
hind foot, 21 mm. Weight of males, 26.5 (24-30) g;
females, 25 (22-28) g.
Distribution in Texas. Throughout the
Trans-Pecos (except for the southeastern part) and a few
counties east of the Pecos River.
Habits. This mouse chiefly
inhabits the low, arid, sandy or gravelly desert areas
where vegetation in the form of creosote bush, mesquite,
yucca, lechuguilla, condalia, and so forth is sparse and
scattered. It lives in burrows of its own or in those it
usurps from other small rodents. Like the northern
grasshopper mouse, it is relatively rare in most
Its behavior and feeding habits are
similar to those outlined for O. leucogaster. Breeding
begins in late January or early February and continues
into September. Gravid females have been captured as
early as February 27 and as late as September 5. The
litters vary in size from two to seven; average 4.2.
Half-grown young have been captured in April, June, July,
and August, suggesting that two, or even three, litters
are produced each year. The young grow rapidly and
females become sexually mature when 7 or 8 weeks of age.
A young female can give birth to her first litter at the
age of 4 months. The gestation period is 26-35 days.
Remarks. In previous editions,
the scientific name for this rodent was reported as Onychomys
torridus; however, recent genetic work on the species
has indicated that formerly, two species have been
included under that name. Consequently, the species
occurring in Texas has been renamed O. arenicola,
with O. torridus occupying southwestern New Mexico
Photo courtesy of University of California Museum
of Vertebrate Zoology.