Damage and Damage Identification

Historically, kangaroo rats were considered to be of relatively minor economic importance. They have come into direct conflict with human interests, however, with large-scale development of sandy soil areas for sprinkler-irrigated corn and alfalfa production. A primary conflict develops at planting time when kangaroo rats dig up newly planted seeds and clip off new sprouts at their base. Damage is more severe when population densities are high. Smaller populations apparently are able to subsist on waste grain and damage is not as apparent. Since kangaroo rats are primarily seed eaters, they find irrigated fields and pastures a veritable oasis and feed extensively on waste grain after harvest.

The Ord’s kangaroo rat, Dipodomys ordi.

Kangaroo rats have foiled attempts to restore overused rangelands. Their habit of collecting and caching large numbers of grass seeds restricts the natural reseeding process. In semiarid rangelands, activities of kangaroo rats can prevent an area from making any appreciable recovery even though the area received complete rest from livestock grazing for 5 years or more. Reducing livestock grazing is not enough. As long as kangaroo rats remain in an area, they will restrict the reestablishment of desirable forages, particularly native grasses.

Legal Status

Most kangaroo rats are considered nongame animals and are not protected by state game laws. Certain local subspecies may be protected by regulations regarding threatened and endangered species. Consult local authorities to determine their legal status before applying controls.

Attention!! Five kangaroo rat species currently are listed as endangered by the US Fish and Wildlife Service. They are found mostly in California and include the Fresno kangaroo rat (D. nitratoides exilis), giant kangaroo rat (D. ingens), Morro Bay kangaroo rat (D. heermanni morroensis), Stephens’ kangaroo rat (D. stephensi including D. cascus), and Tipton kangaroo rat (D. nitratoides nitratoides). Persons working in California, southern Oregon, south central Nevada, and western Arizona should have expertise in identifying these species, their mounds, and the ranges in which they likely occur.

Economics of Damage and Control

Wood (1969) found that Ord’s kangaroo rats eat about 1,300 pounds (585 kg) of air-dried plant material per section per year in south central New Mexico based on average (medium) densities. He also reported an additional 336 pounds (151 kg) of air-dried plant material per section per year consumed by bannertail kangaroo rats in the same area under average (medium) population densities. These data were for arid rangelands and could be higher if the populations of either species were denser. This forage loss (3 Animal Unit Months [AUMs]) is currently valued at $6 to $12 per section in New Mexico. Bannertail kangaroo rats stored 2.9 tons (2.6 mt) of plant material per section per year in their burrows. Furthermore, productions of grasses on rangelands in excellent condition were reduced by 10.6% (or 12 AUMs) by denuding of areas in the vicinity of kangaroo rat mounds. These estimates do not include the loss of regeneration of desirable grasses due to seed consumption.

In areas that are being farmed for production of pasture or commercial crops, densities of kangaroo rats could become much higher than those reported by Wood (1969). These higher densities, coupled with higher crop values, could conceivably produce losses greater than $100 per acre ($250/ha).

The cost of controlling kangaroo rats can be quite high if labor-intensive methods are employed. Of course, the cost per mound will be higher when controlling a few mounds rather than larger numbers. Trapping is the most costly method; toxicants the least costly. The cost of the traps varies greatly, depending on the size, number, and kind of traps used. Live traps cost more than snap traps. The cost of toxic baits is relatively low on a per-mound basis. Labor costs are reduced when large areas are treated with toxic grain baits using a four-wheel, all-terrain cycle.

Information on specific control techniques and limitations can be obtained from your local extension agent or extension wildlife specialist. In addition, personnel from state wildlife agencies or USDA-APHIS-Wildlife Services can provide information on control measures available in your area.