||The Mammals of Texas -
Rodentia : Family Muridae : Peromyscus
attwateri J.A. Allen
Description. A medium-sized Peromyscus
with the tail about as long as (or slightly longer than)
the head and body, moderately haired, darker above than
below (but not sharply bicolor) and usually with a
terminal tuft; hind foot large (24-27 mm); ankles usually
dark or dusky; dorsal color near sayal brown, darker and
mixed with blackish along midline; sides pinkish
cinnamon; ventral color pure white, the bases of the
hairs plumbeous; length of maxillary tooth row 4 mm or
more; each large upper and lower molar has an accessory
Figure 6). External
measurements average: total length, 198 mm; tail, 103 mm;
hind foot, 25 mm. Weight of adults, 25-35 g.
Distribution in Texas. Occurs in central
part of state southward to Uvalde, Medina, and Bexar
Habits. P. attwateri
inhabits the cliffs and rocky outcrops of the Edwards
Plateau, the West Cross Timbers, the Rolling Plains, and
the escarpment of the Llano Estacado in Texas. Vernon
Bailey recorded that in the vicinity of Kerrville he
caught many of them in traps set in crevices along the
cliffs, under logs in the woods, and under fallen grass
and weeds on a creek bank in the bottom of a gulch, as
well as under heaps of driftwood. They seem to prefer
rocky areas where the dominant vegetation is juniper.
They are adept at climbing. Charles Long recorded that,
when compared with other species of Peromyscus, P.
attwateri is a superior and more cautious climber,
seldom jumps from high places when under stress, and is
more capable of finding its way in darkness. Recent
studies using tagged P. attwateri have shown that
this mouse, at least in some areas, is semi-arboreal and
travels frequently in trees.
Where P. attwateri and P. pectoralis co-exist, P. pectoralis specializes in
areas of rock ledges and leaf litter, whereas P.
attwateri is more of a habitat generalist and may be
found not only in areas of rock ledges and leaf litter
but also more open, grassy areas with only scattered rock
Their main diet is plant material,
especially seeds. In southern Missouri, Larry Brown found
that about 70% (by volume) of the stomach contents he
examined consisted of plant material, including fragments
of seeds, berries, bulbs, and green plants. The balance
consisted of insects, chiefly camel crickets and beetles.
In an ecological study of this mouse in
Lynn County, Texas, Herschel Garner found that
reproductive activity began in late September and
continued throughout the winter. He found no evidence of
their breeding during late spring and summer. The number
of young per litter varies from one to six and averages
about four. Based on data derived from the retrapping of
marked animals, Larry Brown estimated the average
lifespan to be 6.8 months with a maximum of 18 months.
Remarks. Peromyscus attwateri
was formerly treated as a subspecies of P. boylii until one of us (Schmidly) removed attwateri
and returned it to its original status as a full species.
This taxonomic change was based primarily on
characteristics of the karyotype (attwateri has
six large biarmed autosomal chromosomes compared to only
two in boylii from west Texas). In addition to
chromosomal differences, the most useful morphological
features available in the field, and to those not trained
in cytogenetics, that separate P. attwateri from P.
boylii are: (1) larger hind foot (24-27 mm in attwateri
and 20-23 mm in Texas-taken boylii) and (2) the
structure of the molar teeth. In attwateri an
accessory loph is present in both the upper and lower
molars, but that structure is absent from the lower
molars of boylii (see Figure 6).