The Pocket Gopher Article by Matt Oliver Copyright © 2003 by ProGardenBiz ProGardenBiz, an online magazine http://www.progardenbiz.com
Pocket gophers (Tomomys spp.), so named for their fur lined cheek pouches located outside mouth on each side of face, are burrowing rodents. They are a serious and difficult to control pest for both Agricultural and Landscape Industries, as well as homeowner. They destroy vegetation, damage machinery (such as mowers), damage irrigation systems and underground wiring, and lower aesthetic value of landscape. In addition, their burrowing activity on slopes causes erosion and can be a major factor in slope weakening and instability that may ultimately lead to a slope failure. Pocket gophers were identified as a major contributing factor to slope failure in a number of recent litigation cases in California.
A thorough understanding of gopher biology and habits is helpful, if not necessary, to a successful control program. They are medium sized rodents with head and body ranging in size from 6-8 inches (15-20 cm) long. They have a powerfully built upper body, short neck and legs, long clawed forefeet, and two pairs of large incisors protruding beyond mouth. These fossorial features are tremendous adaptations for their underground existence. They have a keen sense of touch, thanks to their tail (short and sparsely haired) and vibrissae (whiskers), which serve as sensory organs helping to guide gopher throughout its burrow system. Fur color is highly variable, ranging from dark brown to very light tan.
- Pocket gophers do not hibernate and are thought to be active year round even with snow on ground, but do noticeably decrease surface feeding and mounding in very hot weather. Females produce 1-3 litters per year with an average size surviving brood of 5-6. In unirrigated natural areas breeding season is after rains begin -- which may mean only one litter per year. In irrigated, landscaped areas continual source of green foliage allows female to raise 3 litters per year.
They are territorial, anti-social, and live solitary except during breeding periods and when young are being raised. Gophers live almost exclusively underground, venturing above only to push excavated dirt from burrow system, graze on vegetation near burrow openings, or for purpose of migrating into new territory. Migration occurs both by adults -- usually as a result of unfavorable environmental conditions and/or habitat destruction (e.g. construction projects), and young which mother expels from her burrow system when they are about half grown.
Burrow systems consist of a main tunnel, lateral runs, pop holes, and various other functional tunnels and enlargements which are used for nesting, storage (food caches), resting, eating, etc. The main burrow is usually 2-4 inches in diameter (averaging 2 1/2") and is 2-18 inches below and parallel to ground surface. Burrows of young may be small, covering only one or two hundred square feet while those of older pocket gophers may cover an area as large as three thousand square feet. Lateral runs branch off main run and are used primarily to push excavated soil to surface. The mounds from these laterals are crescent shaped because soil is pushed with forefeet out of angled lateral to front and sides of opening. Pop holes usually lead straight from surface to main run and are used as an access for feeding on nearby vegetation. All runs leading to surface end in a soil mound or plug which keeps system completely enclosed -- allowing no light to enter, and stabilizing burrow temperature and humidity as much as possible. If a gopher dies, irrigation or rain washes loose soil plugs from lateral runs and pop holes leaving open tunnels. Drainage tunnels are used for water run-off, thus making it difficult to drown a gopher in a well established system.
The rate of mound building varies with season, tempurature, and soil condition, but averages 1-3 mounds per day, during active periods. The depth of active burrows is usually deeper under hot conditions, especially in non-irrigated or infrequently irrigated areas. Mounding often sharply decreases in heat of Summer followed by intensive mounding in Fall. This renewed Fall activity has often been blamed on reinvasion of areas thought to have been controlled in early Summer.
Although many different techniques have been used in gopher control most successful programs usually utilize one or more of following methods: trapping, fumigation, and poison baits.
Trapping is an effective method in small areas such as a homeowner situation, or as a follow up to fumigation or baiting, but is time consuming and thus not very cost effective in a large scale program. The most commonly used traps are Macabee trap and box trap. Traps should always be placed in main burrow.
To locate main burrow, look for freshest mounds since they indicate an area of recent gopher activity. You will usually see a small circle or depression representing plugged lateral tunnel. This plug is generally surrounded on one side by soil, making mound form a crescent shape. The main tunnel is usually found 3-1/2 inches from plug side of mound, and is most often between two mounds. Locating main burrow usually requires practice, but your skill will improve with experience.