Pocket gophers

Pocket gophers are one of the most prevalent and destructive vertebrate pests in the Pacific Northwest (Figure 1).

Pocket gophers are burrowing rodents that get their name from the fur-lined, external cheek pouches they use for carrying food and nesting materials. Pouches are located outside the mouth on both sides of the face. Pocket gophers are 5-14 inches (12.7-35.5 cm) long and have soft fur, ranging in color from black to varying shades of brown. Some species can be yellow to almost white.

Pocket gophers are well equipped for digging and tunneling. They have powerfully built forequarters; large-clawed front paws; fine, short fur that does not cake in wet soils; small eyes and ears; and flat heads and short necks. Pocket gopher lips close behind four large incisor teeth to keep soil out of their mouths while digging, leaving their big, yellow incisors visible. Highly sensitive facial whiskers and tails help pocket gophers move in the dark. The tail is sparsely covered with hair and has the unique function of helping to regulate body temperature. Pocket gophers have a keen sense of smell, which enables them to find food.

Biology

Pocket gophers become sexually mature at one year of age and can live for three to five years. They breed in the spring and produce one or two litters per year, averaging three to six young per litter. In irrigated alfalfa fields, it is not uncommon for pocket gophers to have up to three litters per year. The gestation period is 20 days for most pocket gopher species. Births occur from March through June.

Pocket gophers do not hibernate and are active year-round. They are territorial and antisocial. There is normally only one pocket gopher per burrow system, unless it is mating or is a female raising a litter.

Pocket gophers reside in varying geographical elevations, soils and conditions. They occupy rocky areas, but prefer fine-textured, deep, porous soils that are conducive to digging and feeding. Soils that do not hold tunnels (sandy soils) and those that do not diffuse air for breathing (high moisture, clay based soil textures) limit populations. Deep soils are also important for insulating pocket gophers from extreme temperatures. Vegetation with large, fleshy roots or tubers creates ideal habitat.

Burrows consist of a main tunnel and several lateral tunnels, which are linear or branched. Tunnels are about 2 1/2-3 1/2 inches (6.4-8.9 cm) in diameter. Tunnels always slope toward the ground surface because pocket gophers do not make straight vertical tunnels. For the most part, pocket gophers remain underground, although they are sometimes seen feeding at the edge of an open burrow, pushing soil out of a burrow or moving to a new area. They rarely venture more than 2 1/2 feet (0.76 m) from a burrow entrance.

Damage

Pocket gophers feed underground on roots and tubers and cut plant stems belowground to pull plants into the burrow. They acquire water from the vegetation they feed on and do not need to leave the burrow to drink. Pocket gophers will consume any edible plant material, including green, succulent vegetation; roots; bulbs and tubers; grasses and seeds; forbs; tree roots and bark; and legumes with palatable roots, such as alfalfa and clovers. Annual crops, such as grains and annual grasses, are not ideal habitat for pocket gophers because their shallow, fibrous root system does not provide a good food source.

Alfalfa is one of the best food sources and habitat for pocket gophers. Pocket gophers are very destructive to alfalfa fields, feeding on alfalfa taproots and killing the plants. Pocket gopher damage to alfalfa is permanent and will continue to affect field productivity throughout the life of the stand.

ln irrigated cropping systems, pocket gophers damage irrigation lines, divert water by burrowing through ditches and dikes, degrade canals and levees, and cause soil erosion problems and various structural failures.

Pocket gophers can also be very destructive to tree nurseries, orchards and vineyards, especially during the winter, when food sources are limited. Pocket gophers will gnaw and feed on the bark around the base of trees, shrubs and vines, especially when there is snow cover. This damage will reduce plant health and may kill the plant.

Management

Physical

Trapping

• Trapping is a safe and effective control method for small areas or light infestations. It may not be practical or economical for large acreages or for heavy infestations. Trapping can be done year-round but it is difficult when the ground is frozen. Successful pocket gopher trapping requires knowledge and skill. Check publication PNW 627 for additional information about pocket gopher trapping.

Combustion

• A mixture of propane (or other explosive gas) and oxygen can be very effective. The gases are forced into the burrow system and ignited. The combustion kills the pocket gopher and collapses the burrow. Collapsing the burrow or a portion of the burrow reduces the chance that another pocket gopher will re-inhabit the burrow system. Using combustion for pocket gopher control can be hazardous to the applicator and must be done with extreme caution.

Cultural

Cultivation

• Tilling, disking and plowing can inhibit pocket gopher activity. Cultivation destroys burrows and mounds and may drive pocket gophers to other locations.

Crop rotation

• Rotating alfalfa and pasture to small grains can be a very effective control measure. Small grains have small, fibrous root systems that do not sustain pocket gophers as well as fleshy, tap-rooted vegetation like alfalfa.

Buffer strips

• Growing a buffer strip of small grains around alfalfa and pastures can discourage large pocket gopher populations. Buffer strips are particularly beneficial if the field is adjacent to an area with a known infestation or to land where pocket gophers cannot be controlled, such as state or federal land. Buffer strips should be approximately 50 feet (15.24 m) wide. If pocket gopher infestations are particularly high, temporary buffer strips might be an economically viable option.

Fencing

• Fences can protect ornamental shrubs and trees. To protect flower beds and vegetable gardens, bury 1/2 to 3/8-inch (1.3-0.95 cm) mesh wire two feet (61 cm) deep, leaving one foot extending aboveground. Lay gravel around cables and encase sprinkler lines in metal for protection.

Biocontrol

Predators

• Predators that feed on pocket gophers include owls, hawks, badgers, coyotes, foxes, bobcats, skunks, weasels, bull snakes and rattlesnakes. However, these predators do not effectively control large populations.

Chemical control using rodenticide baits

Hand and mechanical baiting is utilized using the following rodenticide baits:

• Strychnine
• Zinc phosphide
• Anticoagulants: diphacinone, chlorophacinone

Further reading

Pesticide warning

Always read and follow the instructions printed on the pesticide label. The pesticide recommendations in this University of Idaho webpage do not substitute for instructions on the label. Pesticide laws and labels change frequently and may have changed since this publication was written. Some pesticides may have been withdrawn or had certain uses prohibited. Use pesticides with care. Do not use a pesticide unless the specific plant, animal or other application site is specifically listed on the label. Store pesticides in their original containers and keep them out of the reach of children, pets and livestock.

Trade names — To simplify information, trade names have been used. No endorsement of named products is intended nor is criticism implied of similar products not mentioned.

Groundwater — To protect groundwater, when there is a choice of pesticides, the applicator should use the product least likely to leach.