Pocket Gopher Identification Pocket gophers are fossorial (burrowing) rodents, so named because they have fur-lined pouches outside of the mouth, one on each side of the face. Pocket gopher characteristics These pockets, which are capable of being turned inside out, are used for carrying food. Pocket gophers are powerfully built in the forequarters and have a short neck; the head is fairly small and flattened. The forepaws are large-clawed and the lips close behind their large incisors, all marvelous adaptations to their underground existence. When the roots are damaged by grub worms, it may not be able to absorb the water and nutrients the entire plant needs to function properly, that is why you see your plants, flowers, and your grass droop, turn brown or gray, and eventually die. Aside from damaging your garden, when there is a serious grub worm infestation, it will attract other animals or pests that feed on them, making the problem even more serious. Examples of such creatures that eat grub worms are gophers, and moles. Though these creatures eat grub worms, they leave nasty burrows and instantly damage your lawn or garden. Eliminating Grub Worms and Japanese Beetles who usually lay their eggs during early summer, will limit your pocket gopher and mole problem. Gophers have small external ears and small eyes. As sight and sound are severely limited, gophers are highly dependent on the sense of touch. The vibrissae (whiskers) on their face are very sensitive to touch and assist pocket gophers while traveling about in their dark tunnels. The tail is sparsely haired and also serves as a sensory mechanism guiding gophers’ backward movements. The tail is also important in thermoregulation, acting as a radiator. Pocket gophers are medium-sized rodents ranging from about 5 to nearly 14
inches (13 to 36 cm) long (head and body). Adult males are larger than adult
females. Their fur is very fine, soft, and highly variable in color. Colors
range from nearly black to pale brown to almost white. The great variability in
size and color of pocket gophers is attributed to their low dispersal rate and
thus limited gene flow, resulting in adaptation to local conditions. Thirty-four species of pocket gophers, represented by five genera, occupy the western hemisphere. In the United States there are 13 species and three genera. The major features differentiating these genera are the size of their forefeet, claws, and front surfaces of their chisel-like incisors. These three genera of pocket gophers can be differentiated by relative size of forefeet and front surfaces of upper incisors. Pappogeomys have a single groove on each upper incisor, and like Geomys, have large forefeet with large claws. Yellow-faced pocket gophers (Pappogeomys castanops) vary in length from slightly more than 5 1/2 to just less than 7 1/2 inches (14 to 19 cm). Their fur color varies from pale yellow to dark reddish brown. Their underparts vary from whitish to bright yellowish buff. Some hairs on the back and top of the head are dark-tipped. General Biology, Reproduction, and Behavior Just as cheek pouches are used in identification of pocket gophers, their fan-shaped soil mounds are characteristic evidence of their presence. Typically, there is only one gopher per burrow system. Obvious exceptions are when mating occurs and when the female is caring for her young. All pocket gophers use their claws and teeth while digging. Geomys, however, are primarily claw diggers, while Thomomys do much more tooth digging, and Pappogeomys are intermediate between the two. Soil, rocks, and other items loosened by this means are kicked away from the digging area with the hind feet. Gophers then turn over, making a sort of somersault within the confines of their burrow, and use their forefeet and chest to push the materials out of the burrow. The incisors of pocket gophers, as in all rodents, grow continuously to repair the wear and tear on the teeth. On the other hand, gophers must gnaw continuously to keep their teeth ground to an appropriate length. Gophers exert tremendous pressure with their bite, up to 18,000 pounds per square inch (1,265 kg/cm2). Burrow Systems consist of a main burrow, generally 4 to 18 inches (10 to 46 cm) below and parallel to the ground surface, with a variable number of lateral burrows off the main one. These end at the surface with a soil mound or sometimes only a soil plug. There are also deeper branches off the main burrow that are used as nests and food caches. Enlargements along the main tunnel are probably feeding and resting locations. Nest chambers have dried grasses and other grasslike plants formed into a sphere. The maximum depth of at least some portion of a burrow may be as great as 5 or 6 feet (1.5 or 1.8 m). The diameter of a burrow is about 3 inches (7.6 cm) but varies with the body size of the gopher. Burrow systems may be linear or highly branched. The more linear systems may be those of reproductive males, since this shape would increase the likelihood of encountering a female’s burrow. The number of soil mounds on the surface of the ground may be as great as 300 per animal in a year. Burrows are sometimes quite dynamic, with portions constantly being sealed off and new areas excavated. A single burrow system may contain up to 200 yards (180 m) of tunnels. The poorer the habitat, the larger the burrow system required to provide sufficient forage for its occupant. The rate of mound building is highly variable. Estimates include an average of 1 to 3 per day, and up to 70 mounds per month. This activity brings large amounts of soil to the surface, variously estimated at 2 1/4 tons (2 mt) per gopher each year, or 46 3/4 tons per acre (103.9 mt/ha) for a population of 50 southern pocket gophers. The tunnel system tells us much about its inhabitant. The system is rigorously defended against intruders and constitutes the home range of the pocket gopher, which may be up to 700 square yards (560 m2). Pocket gophers also tunnel through snow, above the ground. Soil from below ground is pushed into the snow tunnels, but mounds are not built. When the snow melts, the soil casts (tubes) remain on the ground until they weather away. Soil casts are left by both Thomomys and Geomys in areas where snow cover is adequate for burrowing. Pocket gophers do not hibernate. Some observers believe their activities peak at dawn and dusk, but various studies have shown them to be active throughout the day, with activity periods interspersed with rest. Mound building by plains pocket gophers increases in spring, frequently declines during summer, and increases again in fall. In Thomomys, mound building increases from spring through summer into fall. Tunneling underground is a tremendously demanding activity estimated to require 360 to 3,400 times the energy of moving across the surface. Thus, this activity must be of great importance to the pocket gopher’s survival, either increasing its chance of breeding, or finding needed food resources. Pocket gophers reach sexual maturity in the spring following their birth. In the northern part of their range they have 1 litter per year. In the southern portion they may have 2 litters per year. One researcher has suggested that Thomomys in irrigated alfalfa in California may breed throughout the year. Litter sizes range from 1 to 10 but typically average 3 to 4. In some southern portions of their range where 2 litters are born each year, litter size is usually smaller, averaging about 2. The breeding season also varies, but births typically occur from March through June. The gestation period is 18 or 19 days for the northern pocket gopher, but periods as long as 51 days for the plains pocket gopher have been reported. Sex ratios are typically in favor of females, generally ranging from 55% to 60% females for Geomys. In Thomomys, the sex ratio is often 50:50 but it varies seasonally. There may be more males than females in spring, and the reverse for summer and fall. Pocket gophers have been thought to be polygamous (one male mating with two or more females), but serial monogamy may be the case. The male cohabits a tunnel system and may help care for young before moving on to another female’s burrow system. Some researchers believe both sexes move mainly underground from their own to other burrows during the breeding season. Densities reported for various pocket gophers are highly variable. Densities of 16 to 20 per acre (40 to 49/ha) are very common for Thomomys, but they may attain densities up to 62 per acre (153/ha). For Geomys, 6 to 8 per acre (20/ha) are representative of high densities. Average life span of gophers appears to change inversely with population density. Average longevity for Thomomys ranges from just over 1 year to nearly 3 years. Geomys may live to an average age of 2, and reach a maximum age in the wild in excess of 7 years. Sharp declines in gopher populations have been noted on several occasions. Usually some climatic factor is associated with a marked decline. An example would be a heavy snow cover, then rapid snowmelt with a concomitant rise in the water table. External parasites are often found on pocket gophers. Lice are perhaps the most common, while ticks, fleas, and mites also occur. The contribution of parasites to gopher mortality is unknown. Numerous predators eat pocket gophers. Some of the predators pursue the gopher in its tunnel system (weasels, perhaps spotted skunks, and several snakes including gopher, bull, and rattlesnakes). Badgers are adept at digging out gophers, and a whole host of predators prey on gophers when they are aboveground feeding, dispersing, or while they construct their mounds. Other mammalian predators include coyotes, domestic dogs, foxes, house cats, striped skunks, and bobcats. Raptors that prey on gophers include several owls, especially great horned and barn owls, and several hawks. A great diversity of vertebrates has been found in the burrows of pocket gophers. It is especially interesting to note how gophers react to those animals. Most amphibians and lizards are largely ignored. Ground squirrels, kangaroo rats, and smaller rodents generally avoid gophers, frequently leaving the tunnel system if occupied by a gopher. Sometimes gophers block the exit of these rodents by constructing earthen plugs in the burrow system. When pocket gophers encounter snakes, weasels, or other threats, they typically react by assuming a threatening posture with the mouth open, vocalizing with panting sounds, and raising the front of the body slightly with their claws extended forward. This behavior usually chases away other gophers in the tunnel. If the intruder is a snake, many strikes bounce off the gopher’s incisors and claws. In addition, the gopher may try to block the intruder with a wall of soil. Pocket gophers are capable of swimming. The southern pocket gopher has the greatest endurance of three species that were tested in laboratory conditions. The plains pocket gopher is intermediate in its endurance between the southern pocket gopher and the yellow-faced pocket gopher. The latter is a very poor swimmer. The superior swimming ability of the southern pocket gopher may be an adaptation to its mountain habitat, which frequently undergoes flooding during snowmelt. Swimming during flooding may also be a method of pocket gopher dispersal. Dispersal of young plains pocket gophers from their natal burrows has been reported to begin in June in Colorado. Young apparently begin to disperse when they are only one-third the adult body size. Other indications of aboveground dispersal of pocket gophers have been reported by incidental captures of gophers in drift fences set for snakes. A plains pocket gopher was reported a victim of an automobile on a highway in Iowa, and plains pocket gophers are reported falling into window wells every summer in Nebraska. These aboveground movements are a prime reason for high mortality in densely populated areas.