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Gophers

Identification

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. Thomomys have smooth-faced incisors and small forefeet with small claws. Northern pocket gophers (Thomomys talpoides) are typically from 6 1/2 to 10 inches (17 to 25 cm) long. Their fur is variable in color but is often yellowish brown with pale under parts. Botta’s (or valley) pocket gophers (Thomomys bottae) are extremely variable in size and color. Botta’s pocket gophers are 5 inches to about 13 1/2 inches (13 to 34 cm) long. Their color varies from almost white to black. Geomys have two grooves on each upper incisor and large forefeet and claws. Plains pocket gophers (Geomysbursarius) vary in length from almost 7 1/2 to 14 inches (18 to 36 cm). Their fur is typically brown but may vary to black. Desert pocket gophers (Geomysarenarius) are always brown and vary from nearly 8 3/4 to 11 inches (22 to 28 cm) long. Texas pocket gophers (Geomys personatus) are also brown and are from slightly larger than 8 3/4 to nearly 13 inches (22 to 34 cm) long. Southeastern pocket gophers (Geomyspinetis) are of various shades of brown, depending on soil color, and are from 9 to 13 1/4 inches (23 to 34 cm) long. 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. The under-parts vary from whitish to bright yellowish buff. Some hairs on the back and top of the head are dark-tipped.

Range

Pocket gophers are found only in the Western Hemisphere. They range from Panama in the south to Alberta in the north. With the exception of the south-eastern pocket gopher, they occur throughout the western two-thirds of the United States.

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. These pockets, which are capable of being turned inside out, are used for carrying food. Pocket gophers are powerfully built in the fore-quarters 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 under-ground existence. 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.

Food Habits

Pocket gophers feed on plants in three ways: 1) they feed on roots that they encounter when digging; 2) they may go to the surface, venturing only a body length or so from their tunnel opening to feed on aboveground vegetation; and 3) they pull vegetation into their tunnel from below. Pocket gophers eat forbs, grasses, shrubs, and trees. They are strict herbivores, and  any animal material in their diet appears to result from incidental ingestion. Alfalfa and dandelions are apparently some of the most preferred and nutritious foods  for pocket gophers. Generally, Thomomys prefer perennial forbs, but they will also eat annual plants with fleshy underground storage structures. Plains pocket gophers consume primarily grasses, especially those with rhizomes, but they seem to prefer forbs when they are succulent in spring and summer. Portions of plants consumed also vary seasonally. Gophers utilize above-ground portions of vegetation mostly during the growing season, when the vegetation is green and succulent. Height and density of vegetation at this time of year may also offer protection from predators, reducing the risk of short surface trips. Year-round, however, roots are the major food source. Many trees and shrubs are clipped just above ground level. This occurs principally during winter under snow cover. Damage may reach as high as 10 feet (3 m) above ground. Seedlings also have their roots clipped by pocket gophers.

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/cm 2 ). 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 grass like 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 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 up to 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 m 2 ). 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 through-out 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 another female’s burrow system. Some researchers believe both sexes move mainly underground from their own to other burrows during the breeding season. 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.

Damage and Damage Identification

Several mammals are sometimes confused with pocket gophers because of variations in common local terminology.  In addition, in the south-eastern United States, pocket gophers are called “salamanders,” (derived from the term sandy mounder), while the term gopher refers to a tortoise. Pocket gophers can be distinguished from the other mammals by their tell-tale signs as well as by their appearance. Pocket gophers leave soil mounds on the surface of the ground. The mounds are usually fan-shaped and tunnel entrances are plugged, keeping various intruders out of burrows. Damage caused by gophers includes destruction of underground utility cables and irrigation pipe, direct consumption and smothering of forage by earthen mounds, and change in species composition on rangelands by providing seedbeds (mounds) for invading annual plants. Gophers damage trees by stem girdling and clipping, root pruning, and possibly root exposure caused by burrowing. In irrigated areas,  gopher tunnels can channel water runoff, causing loss of surface irrigation water. Gopher tunnels in ditch banks and earthen dams can weaken these structures, causing water loss by seepage and piping through a bank or the complete loss or washout of a canal bank. The presence of gophers also increases the likelihood of badger activity, which can also cause considerable damage. 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.

 

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Did you Know

Food left out for household pets is often equally attractive to some wildlife species. In these situations, the wildlife have suitable food and habitat and will usually become a nuisance.

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