Plains Pocket Gopher
Order Rodentia : Family Geomyidae : Geomys bursarius (Shaw)

Description. These are medium to small sized, dark brown gophers with large, furlined cheek pouches. The body is thick-set and appears heaviest anteriorly, from which it gradually tapers to the tail, widening a little at the thighs. The eyes are tiny and beadlike, and the ears are very rudimentary, represented only by a thickened ridge of skin at the base. Long curved claws are present on the front feet for digging; the claws on the hind feet are much smaller.

The dental formula is I 1/1, C 0/0, Pm 1/1, M 3/3 X 2 = 20. The upper incisors have two grooves. External measurements average: total length, 236 mm; tail, 65 mm; hind foot, 31 mm. Weight: males, 180-200 g; females, 120-160 g.

Distribution in Texas. Northwestern and north-central Texas, south to Midland and Tom Green counties in west and to McLennan County in east. Grayson and Dallas counties appear to be the eastern limit of this species in Texas.

Habits. This pocket gopher typically inhabits sandy soils where the topsoil is 10 cm or more in depth. Clayey soils are usually avoided. These gophers live most of their solitary lives in underground burrows, coming to the surface only to throw out earth removed in their tunneling and to forage for some items of food. They seldom travel far overland. The average diameter of 40 burrows examined in Texas was nearly 6 cm; the average depth below the surface, 14 cm, with extremes of 10 cm and 67.5 cm. Much of their burrowing is done in search of food. The underground galleries attain labyrinthine proportions in many instances because the tunnels meander aimlessly through the feeding areas. This is particularly noticeable under oak trees that have dropped a good crop of acorns. Burrows have been examined that extend well over 100 m, excluding the numerous short side branches. Only one adult gopher normally occupies a single burrow system.

The average mound thrown up by these gophers is about 30 by 45 cm, about 8 cm in height, and crescentic in outline. The opening through which the earth is pushed is usually plugged from within. The gopher digs with its front claws and protruding teeth, shoves the loose earth ahead of it with its chin and forefeet, and uses the hind feet for propulsion. The ceaseless energy of these subterranean miners is suggested by the size of the huge winter mounds they make in sites that have poor underground drainage. One of these was 2 m long, 1.5 m wide, 60 cm high, and weighed an estimated 360 kg. The female that occupied this mound weighed 150 g. A typical winter mound contains numerous galleries, a nest chamber, a toilet, and food storage chambers.

These rodents feed on a variety of plant items, chiefly roots and stems of weeds and grasses. Most plant food is encountered and ingested while the gopher digs, but some "grazing" of food present along burrow walls probably also occurs. The furlined cheek pouches are used to carry food and nesting material but never dirt. Captive gophers have eaten white grubs, small grasshoppers, beetle pupae, and crickets. Earthworms and raw beef were ignored.

Breeding begins in late January or early February in eastern Texas and continues for a period of some 3 or 4 months. One litter a year, or two in quick succession, appears to be the rule. The young, usually two or three in number, are born from March to July. The young are nearly naked, blind, and helpless at birth. They remain with their mother until nearly full-grown and then are evicted to lead an independent life.

As long as they remain in their burrows, pocket gophers are relatively safe from predators other than those which are specialized for digging, such as badgers and long-tailed weasels. However, when a gopher leaves its burrow it is highly vulnerable, and most predation losses probably occur on the surface. Known predators, other than those mentioned above, include coyotes, skunks, domestic cats, hawks, owls, and several kinds of snakes. As a result of the protection offered by the burrow, pocket gophers are long-lived relative to many other rodents, insectivores, and lagomorphs, living an average of 1-2 years in the wild.

In farming regions these rodents can be destructive to crops and orchards. The amount of damage is closely associated with the number of animals. The average population density in eastern Texas is about 3.2 gophers per ha. The highest population density of record is 17.6 per ha. These gophers can be controlled on small areas by trapping and on large ones by placing poisoned grain in their burrows.

Remarks. Historically, Geomys bursarius has been considered one wide ranging, but morphologically variable species that was distributed over most of the Great Plains and south-central United States, including the Texas Panhandle and eastern Texas. However, recent studies by specialists trained in cytological and biochemical taxonomy have revealed that in actuality there are five species of pocket gophers ranging over these regions of Texas (designated G. bursarius, G. attwateri, G. breviceps, G. knoxjonesi, and G. texensis). These are considered cryptic species, meaning that they cannot be differentiated on the basis of observed morphological characteristics although they are genetically distinct. Karyotypic, electrophoretic, and mitochondrial DNA data are required to confidently distinguish questionable specimens, although all appear to be allopatric in range.

Photo credit: L. K. Couch.