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Damage and Damage Identification
Several mammals are sometimes confused with pocket gophers because of variations in common local terminology. In addition, in the southeastern 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 telltale 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 pocket 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 range-lands by providing seedbeds (mounds) for invading annual plants. Gophers damage trees by stem girdling and clipping, root pruning, and possible root exposure caused by burrowing. Gopher mounds dull and plug sicklebars when harvesting hay or alfalfa, and soil brought to the surface as mounds is more likely to erode. In irrigated areas, gopher tunnels can channel 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.
There are several types of poisons and gas cartridges on the market for controlling gophers, however 100% control will rarely be achieved with these methods. The most successful way to eliminate gopher problems is by trapping them.
Pocket Gopher Removal and Control Methods
Pocket gopher sign includes large unsightly mounds in yards and mounds in hay fields. The tunnels connecting these mounds are usually 12 - 18 inches underground. Pocket Gopher damage includes chewing of any underground lines including electric, water and septic piping. In addition to this they also will eat the roots of flowers, vegetables, hay, and occasionally tree roots.
For most people the easiest way to control pocket gophers is by trapping them. To find the pocket gopher runs either dig into the mound to find the run or probe outside the mound using a long smooth rod to find the run then dig down to it. The pocket gopher traps are placed in each tunnel leaving the tunnel open. When the pocket gopher feels the air draft the open tunnel causes it will immediately attempt to plug the open tunnel. The best trap for pocket gophers is the Cinch Sure trap, this trap is more sensitive than others and has far fewer misses (plugged traps) than the others.
The best trap for pocket gophers is the Cinch Sure trap; this trap is more sensitive than others and has far fewer misses (plugged traps) than the others.
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 the 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 squared).
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 to 1.8 m). The diameter of a burrow is about 3 inches (7.6 cm) but varies with the size of the gopher.
Burrow systems may be linear or highly branched. the more linear systems may be those of reproductive males, since their 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 per 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 pf 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 21/2 tons (2 mt) per gopher each year up to 463/4 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 squared).
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 then increases during 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 chances 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 the 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 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 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 2 or more females), but serial monogamy mat be the case. The male cohabits a tunnel system and may help care for the 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 40 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 (2- ha) are representative of high densities. Average life span of gophers appears to change with population density. Average longevity for Thomomys ranges from just over 1 year to nearly 3 years. Geomys may live to an average 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 snow melt 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 tunneling 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 above ground feeding, dispersing, or while they construct 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 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 other gophers away in the tunnel. If the intruder is a snake, many strikes bounce off the gophers 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 the 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 its 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 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 above ground movements are a prime reason for high mortality in densely populated areas.