Pocket Gopher Damage Assessment

Plains pocket gopher, Geomys bursarius

Damage and Damage Identification

Several mammals are sometimes confused with pocket gophers because of variations in common local terminology (Fig. 5). 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 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.

Figure 5. Mammals that are sometimes called gophers. From top to bottom: Richardson ground squirrel, thirteen-lined ground squirrel, vole, and mole.

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. Gopher mounds dull and plug sickle bars 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 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.

Legal Status

Pocket gophers are not protected by federal or state law.

Economics of Damage and Control

It is relatively easy to determine the value of the forage lost to pocket gophers. Botta’s pocket gophers at a density of 32 per acre (79/ha) decreased the forage yield by 25% on foothill rangelands in California, where the plants were nearly all annuals. Plains pocket gophers reduced forage yield on rangelands in western Nebraska by 21% to 49% on different range sites. Alfalfa yields in eastern Nebraska were reduced as much as 46% in dryland and 35% in irrigated alfalfa. Losses of 30% have been reported for hay meadows.

Calculating the cost of control operations is only slightly more complicated. However, the benefit-cost analysis of control is still not straight-forward. More research data are needed on managing the recovery of forage productivity. For example, should range be fertilized, rested, or lightly grazed? Should gopher mounds on alfalfa be lightly harrowed? A study of northern pocket gopher control on range production in southern Alberta indicated that forage yields increased 16%, 3 months after treatment. The potential for complete yield recovery the first year following gopher removal has been noted for a fibrous-rooted variety of alfalfa.

Economic assessment should also be made to determine the cost of no control, the speed of pocket gopher infestation, and the costs associated with dulled or plugged mowing machinery or mechanical breakdowns caused by the mounds. Assessment could also be made for damages to buried cable, irrigation structures, trees, and so on.

The benefits of pocket gophers also complicate the economic analysis. Some of these benefits are: (1) increased soil fertility by adding organic matter such as buried vegetation and fecal wastes; (2) increased soil aeration and decreased soil compaction; (3) increased water infiltration and thus decreased runoff; and (4) increased rate of soil formation by bringing subsoil material to the surface of the ground, subjecting it to weathering.

Decisions on whether or not to control gophers may be influenced by the animals’ benefits, which are long-term and not always readily recognized, and the damage they cause, which is obvious and sometimes substantial in the short-term. Landowners who are currently troubled by pocket gophers can gain tremendously by studying the gophers’ basic biology. They would gain economically by learning how to manage their systems with pocket gophers in mind, and aesthetically by understanding how this interesting animal “makes a living.”

The distribution of gophers makes it unlikely that control measures will threaten them with extinction. Local eradication may be desirable and cost-effective in some small areas with high-value items. On the other hand, it may be effective to simply reduce a population. There are also times when control is not cost-effective and therefore inadvisable. Complete control may upset the long-term integrity of ecosystems in a manner that we cannot possibly predict from our current knowledge of the structure and function of those systems.