Texas Rodents

16 Jan 2022   | Uncategorized

This article by Jerry Cates, first published on 25 January 2015, was last revised on 15 January 2022. © Bugsinthenews Vol. 16:01(02):

The nearly 2,000 species of rodents that are presently recognized worldwide comprise about 40% of all living mammals. 68 rodent species are known to be found in Texas, and 24 of these are found in Central Texas, all fully capable of invading yards, landscapes, and man-made structures.

Rodents are distinguished from other mammals by the kinds and arrangements of their teeth: all rodents have a single pair of upper, and a single pair of lower incisors that are separated, from several pairs of chewing teeth, by a large gap (diastema). The chewing teeth of typical mice consist only of molars, while squirrels and their allies, jumping mice, and cavylike rodents have both molars and premolars. Rodent incisors grow continuously from birth to death, and have chisel-like cutting edges:

Pocket gophers (Geomyidae)

  • Llano pocket gopher (Geomys texensis): subterranean; common in west-central part of Central Texas; small, dark brown or sandy brown on back, paler sides, white underparts; prefers deep sandy loam, gravel, or sand in Texas Hill Country; breeds in spring and early summer.

Pocket mice & kangaroo rats (Heteromyidae)

  • Hispid pocket mouse (Chaetodipus hispidus): terrestrial, throughout Central Texas; head and body 3.75 inches; large and colorful, with brown back, grizzled with orange and black; a broad orange lateral line on sides; white belly, broad orange ring around eye, bicolor tail is short and not tufted; breeds year-round; prefers grassy areas in plains and deserts, usually on sandy soils.
  • Merriam’s pocket mouse (Perognathus merriami): terrestrial, throughout Central Texas; head and body 2.25 in, tail 1.75 in.; breeds Mar-Dec; found on sand, gravel, and hard-packed soils.
  • Silky pocket mouse (Perognathus flavus): terrestrial, throughout Central Texas; head and body 2.25 in.; tail 1.75 in., shorter than other pocket mice; very small; grizzled orange-brown back, with pale orange lateral line, and white belly; sifts through sand for seeds, climbs stalks to harvest green seeds; breeds Mar-Oct; prefers sandy soils, rocky areas, and clays.

Mice & rats (Muridae)

  • Black Rat (Rattus rattus): arboreal, terrestrial, and opportunistically subterranean throughout Central Texas; head and body 5-7 in., tail 3-4 in.; scraggly black to light brown fur with lighter undersides; nocturnal, congregating around warehouses, residential buildings, and similar human settlements; prefer in urban settings to live in palm and pines; nests are ball-shaped and are made of shredded sticks, leaves, vegetation, and cloth; will build nests in abundant leaf litter and thick ground cover and under some circumstances will burrow into the ground; generalist omnivores, adapt to food supplies available locally; excellent vectors for disease transmission due to an ability to carry bacteria and viruses in their blood streams; particularly known to carry Streptococcus pneumoniae, Corynebecterium kutsheri, Bacillus piliformis, Pasteurella pneumotropica, and Streptobacillus moniliformis; preyed on by owls, cats, foxes, and coyotes.
  • Brown Rat (Rattus norvegicus): subterranean, terrestrial, and arboreal throughout Central Texas: head and body 8-10 in., tail 7-10 in.; brown or dark gray back with light gray underparts; nocturnal, excellent swimmer and burrower, often excavating extensive burrow systems; true omnivores, though cereals form substantial part of diet; breed throughout the year, females able to produce 5 litters annually; gestation period is 21 days, pups become sexually mature in five weeks, permitting populations to grow by a factor of 10 in 15 weeks; live in large, hierarchical groups in burrows or subsurface places such as sewers and cellars; generally begin new burrows adjacent to an object or structure, as this provides a roof for the set ion of the burrow nearest to the ground’s surface; burrows develop to include multiple levels of tunnels as well as a secondary entrance; burrows are used to escape perceived threats; carry a number of pathogens and parasites.
  • Deer Mouse (Peromyscus maniculatus): terrestrial, arboreal, and subterranean, throughout Central Texas; head and body 3.5 in., tail 2.25 in.; so closely related to the white-footed mouse (Peromyscus leucopus) that the two are best distinguished via RBC agglutination tests or karyotype techniques, though, physically, the deer mouse is distinguishable by its long, multicolored tail; 66 subspecies are recognized, all are tiny and plentiful throughout their range; nocturnal, foraging by night, spending day in trees or burrows, the latter having nests of plant matter; reproduce throughout the year, esp. Mar-Oct, var. based on food availability; preyed on by snakes, owls, skunks, foxes, and domestic cats.
  • Eastern woodrat (Neotoma floridana): terrestrial, semi-arboreal, and subterranean pack rat, on eastern edge of Central Texas; head and body 9 in., tail 6.25 in., moderately haired; back gray brown, dark brown, or sandy brown; sides washed with buff; belly grayish white or cream white; ears large; eats leaves, fruit, berries, fungi, nuts, and seeds; in east Texas uses underground burrows; breeds year round; common, widespread, and able to thrive in a wide variety of habitats.
  • Fulvous harvest mouse (Reithrodontomys fulvescens): arboreal and terrestrial, on northern, eastern, and southern edges of Central Texas; head and body 2.75 in., with long tail; back rusty brown peppered with black, sides orange, belly white or buff; breeds in spring and fall; constructs baseball sized nests of shredded plant material in vegetation.
  • Hispid cotton rat (Sigmodon hispidus): terrestrial and subterranean throughout Texas; head and body 6 in., tail 4 in.; upper parts grizzled dark brown and buff, belly grayish white; mainly crepuscular but active day or night; eats grass and other plants, insects, and fungi; makes nests in thick grass clumps or short underground burrows.
  • House mouse (Mus musculus): terrestrial, throughout Central Texas; head and body 3-3.9 in., tail 2-3.9 in.; fur light to dark brown; adults are good jumpers, climbers, and swimmers, are crepuscular or nocturnal, sleep 12 or more hours a day, and nest in cryptic places near food sources; naturally omnivorous, but preferentially feeds on plant matter; known to be capable of transmitting a few human diseases, including Lymphocytic choriomeningitis, but such infections are  not commonly reported and, when diagnosed, are generally mild; mice often contaminate food and damage food packaging; mice tend not to be as infested with fleas as rats, and thus are not effective vectors of plague.
  • Northern pygmy mouse (Baiomys taylori): terrestrial and subterranean, throughout Central Texas; head and body 2.5 in., tail 1.75 in.; dark gray-brown back, gray sides, grayish white belly; small eyes, medium ears, tail short and nearly naked; mainly nocturnal but sometimes diurnal; eats seeds, fruit, green vegetation; nest is ball-shaped with one or two openings, and is situated under logs, in vegetation, and in small burrows.
  • Plains harvest mouse (Reithrodontomys montanus): terrestrial, throughout Central Texas; head and body 2.7 in., tail 2.25 in.; feeds on weed flowers and seeds, and on grasshoppers and other invertebrates; nest is ball shaped constructed on or just above the ground; breeds year round; prefers open countryside with short grasses.
  • Southern plains woodrat (Neotoma micropus): terrestrial, in western half of Central Texas; head and body 8.5 in., tail 6 in.; large, with back and sides steely gray or blue-gray, white belly; eats cactus leaves and fruit, mesquite beans, acorns, and plant matter; makes a house under prickly pear cactus, with 2-5 entrances, and likely uses the house for life.
  • Texas mouse (Peromyscus attwateri): terrestrial and semi-arboreal throughout Central Texas; 3.75 in. head and body, 4 in. tail; eats seeds, other plant materials, and insects.
  • White-ankled mouse (Peromyscus pectoralis): terrestrial, throughout Central Texas; head and body 3.75 in., tail 3.75 in.; gray-brown upper parts, brown sides with narrow orange lateral line, white belly; often found on rock ledges and in leaf litter; eats juniper berries, acorns, hackberries, seeds, and invertebrates; breeds year round.
  • White-footed mouse (Peromyscus leucopus): terrestrial, semi-subterranean, and semi-arboreal, throughout central Texas; head and body 3.5 in., tail 3 in.; dark brown upper back, sides orange-brown, white belly; eats seeds, nuts, fruit, invertebrates, and vegetable matter; makes ball-shaped nests in logs, standing trees, abandoned burrows, bird nests, and inside man-made structures; breeds mainly in spring.
  • Woodland vole (Microtus pinetorum); subterranean, throughout Central Texas; head and body 4 in., tail 0.75 in.; reddish brown back, orange-brown sides, gray belly; eyes and ears small; eats roots throughout the year, grass stems in summer, fruit and seeds in the fall, bark in winter; breeds year round; favors sandy soil.

Squirrels (Sciuridae)

  • Black-tailed prairie dog (Cynomys ludovicianus): subterranean; along the western edge of Central Texas; though capable of invading yards and landscapes, it is unlikely to do so.
  • Eastern gray squirrel (Sciurus carolinensis): arboreal and terrestrial; eastern half of Central Texas; uppermost parts gray with yellow-brown cast on upper back and head; white or pale orange eye-ring; ears gray to rusty brown, sometimes white with slight tuft in winter; white belly; mainly arboreal but spends much time on ground; nest made of twigs, leaves, and plant material, in hollow trees or inside hollow trees; each squirrel uses more than one nest; breeds twice a year in Jan-Feb and June-July; favors hardwood forests.
  • Fox squirrel (Sciurus niger): arboreal and terrestrial; throughout Central Texas; variable in color but most commonly grizzled yellow-brown above, with pale orange to rusty brown belly, cheeks, eye-ring and feet, and tail edged in orange-brown; larger than eastern gray squirrel where range overlaps; travels and rests in trees, but feeds extensively on ground; eats nuts, acorns, seeds, fungi, and fruit; makes leaf nests on branches, in hollow trees, or in voids of man-made structures; mates Jan-Feb and May-June; prefers open stands of deciduous and evergreen woodlands, shunning woods with dense undergrowth or closed canopies.
  • Mexican ground squirrel (Ictidomys mexicanus): subterranean and terrestrial; throughout Central Texas; feeds on mesquite leaves and beans, grass and herb seeds, insects, carrion, and small vertebrates. It makes burrows that have multiple entrances, and willingly uses the burrows of pocket gophers. It prefers areas with sandy soils.
  • Rock squirrel (Otospermophilus variegates): arboreal, terrestrial;  throughout Central Texas; in Texas most commonly found with blackish head and shoulders, dark brown or cream forelegs, but can be entirely black with a pale eye-ring and yellowish belly; mostly seen on the ground but capable of climbing well and sometimes nests in trees; eats fruit, seeds, plant matter, roots, cacti, and invertebrates; prefers rocky canyons, cliffs, and hillsides in arid areas.
  • Thirteen-lined ground squirrel (Ictidomys tridecemlineatus): subterranean and terrestrial; along the eastern edge of Central Texas; is the “gopher” most people notice along roadsides, on lawns, and on golf courses. It eats seeds of grasses and herbs, but will also consume small insects and vertebrates. Though they will form colonies when conditions permit, adults are not social and defend only the areas around their nest burrows. Deeper nest burrows are built near shallow escape burrows. They prefer short grass meadows and prairies, and avoid wet, low-lying areas.