This brochure has been prepared to inform South Dakotans about prairie dogs. Some of the benefits of the prairie dog ecosystem are described, as well as areas of conflict. This document also includes information on prairie dog management options and applicator/landowner responsibilities under both federal and state laws and regulations regarding prairie dog management.

The black-tailed prairie dog (Cynomys ludovicianus) is the only prairie dog species in South Dakota. The other species in the genus, the white-tailed prairie dog and Gunnison’s prairie dog, are found throughout the Rocky Mountain states. The impacts and management of these latter two species may be different from those of the black-tailed prairie dog.

Prairie dogs live in ground burrows concentrated in "towns". The average population can vary greatly by area and season. Black-tailed prairie dog towns usually have between 30 and 60 occupied plus unoccupied burrows per acre. Prairie dogs are active during the daylight hours but they may also move between burrows after dark. Young males move to new areas in the late spring, either to neighboring towns or to establish new territories. Although prairie dogs are highly adaptable feeders (grasses, forbs, shrubs, seeds and insects), grasses are their preferred choice.

At one time prairie dogs were estimated to occupy millions of acres throughout the Great Plains and Rocky Mountains States. Prairie dog numbers in South Dakota have varied. In 1968 their numbers were estimated at 61,000 acres, however in 1980 occupied acreage was estimated at 730,000 acres. Currently, there are probably between 200,000 and 250,000 acres of prairie dogs within South Dakota. In South Dakota, their variability has been attributed to agricultural changes in land use as well as long term control effects.

Prairie dogs and their communities are important components of North America’s mid- to short-grass prairie and desert grassland ecosystems. Their presence results in increased wildlife and plant diversity, although these effects vary due to prairie dog abundance, rainfall, soil and other local conditions. In one study forty percent of the 332 vertebrate species found west of the Missouri River used prairie dog colonies for food, shelter or reproduction. Prairie dog grazing, burrowing and digging activities may maintain vegetation in earlier stages, benefit soil organisms, and increase water percolation. However, under some conditions prairie dog activities may contribute to the decline of some plant species and may increase soil erosion.

Prairie dogs generally favor disturbed sites, such as plowed, frequently mowed or heavily grazed areas. Once established, prairie dogs are able to maintain and expand their habitat, especially in the absence of land management changes. Ranchers and farmers often object to prairie dogs on range and pasture lands, because of their impacts on vegetation used for forage and the potential for economic loss.

The management of prairie dogs is a complex issue involving private property rights, state management authorities, and in some cases, federal involvement due to endangered species and their habitat concerns. Private landowners have the right, and in some cases the obligation, to manage prairie dog numbers to reduce rangeland damage or the spread of populations onto adjacent property. Any management efforts must be done in conjunction will all of the above laws and regulations.

When management directs control of prairie dogs, several options exist. Like any pest control operation, an integrated program should be considered. Integrated Pest Management (IPM) principles include considering biological, cultural, mechanical and chemical control options.

Biological control includes control of a pest species by predators, disease, and/or parasites. Biological control, which is an integral part of insect management techniques, has limited application in vertebrate pest management. For prairie dogs, some tests have indicated that providing access for predators, such as corridors where they can approach unnoticed, or perches for raptors can help limit prairie dog town growth or perhaps reduce overall prairie dog numbers. Wide-scale use of these techniques is not a practical prairie dog control option. Diseases, such as plague, often eliminate prairie dog populations in other areas of the US. Plague has not yet been documented in South Dakota. Additionally, diseases are likely to affect only high density populations and are not useful in limiting growth of small towns. Biological control techniques need more testing and evaluation before being recommended for large-scale use.

Cultural control includes manipulation of the habitat through changes in management styles. While prairie dogs appear to be able to maintain their own habitat in short and mixed grass communities, some evidence exists that decreased grazing pressure can disfavor prairie dogs in tall grass communities. In a few instances, prairie dogs disappeared under reduced or eliminated grazing pressure. The application of this method for prairie dog control may have limited use in grazing operations.

One aspect of cultural control that must be considered is land use following chemical prairie dog control. As noted earlier, prairie dogs tend to establish themselves in disturbed areas. Land uses must permit sufficient time for the range to recover to preclude reoccupation. In planning prairie dog control operations, it is best to schedule at least one growing season’s rest for the treated area. More time may be needed to fully recover the area, especially if that season is dry. Failure to allow this recovery will likely result in more prairie dogs at a later date.

Mechanical control includes physically removing prairie dogs through shooting, trapping and fencing. Shooting may be useful in reducing individual prairie dog numbers, but it is not likely to remove all of them. A concentrated prairie dog shooting program requires a great deal of effort. It is likely to remove up to 75% of the prairie dogs, which should keep the town from spreading. The remaining 25% usually become very difficult to remove and will be able to repopulate the town in a single breeding season. Many landowners express the opinion that a few prairie dogs are acceptable and may only wish to initiate control when they occupy large acreage. For these landowners, shooting may be a very viable control technique. Trapping is a very inefficient method of controlling prairie dogs.

Sight barrier fences, those limiting the prairie dogs’ view, are currently experimental, but maybe a useful tool in reducing prairie dog town growth. Livestock fencing that facilitates a planned grazing system may be useful as one tool of a range management plan. Federal cost sharing for livestock fencing may be available from a number of sources.

Chemical control involves the use of rodenticides in lethal control of prairie dogs. Two classes of rodenticides are currently used in prairie dog control: baits and fumigants.

Recently enacted provisions of the 1990 Farm Bill require certified applicators to keep records of the application of restricted use pesticides. These records must include the brand or product name, EPA registration number, total amount of product used, location and size of the area treated, the crop or site treated, month, day and year the application was made and the name and certification following the treatment. Federal regulations permit inspection by a number of sources, but prohibit the release of information that would directly or indirectly identify the applicator. Additional information is available from county Agricultural Extension Agents.

Baits registered for use in prairie dog control include zinc phosphide grain bait. Zinc phosphide has a prominent odor similar to garlic or carbide. The use of zinc phosphide requires pre-baiting with good clean #1 oats (38 lbs/bu or better is preferred), which has been steamed and lightly crimped. Pre-baiting should be done prior to treatment with zinc phosphide oats to assure good acceptance of the treated bait. To pre-bait, place one heaping teaspoon (4 grams) of oats in a prominent solid spot near each mound. The pre-bait should be consumed prior to baiting. Generally, bait may be placed 2 to 3 days following pre-bait, but only if the pre-bait has been accepted. If complications prevent baiting within 10 days of pre-baiting, you should pre-bait again.

The same application procedures apply to the placement of bait. One heaping teaspoon (4 grams) of zinc phosphide treated oats per mound should be scattered over about one square foot of solid ground. It is important that all mounds be treated whether they appear active or not. Even though a prairie dog may not live in a particular burrow, it will still visit and feed at the mounds. If you apply to little bait, your degree of control may suffer. If you apply too much bait, it will remain a hazard to non-target birds and may serve as continued bait aversion to the remaining prairie dogs that consume sub-lethal doses. By following the recommended procedures and treating when acceptance of pre-bait is good, control of 90% of the population can be expected. It is recommended that follow up treatment with zinc phosphide treated grain bait not be attempted for the remainder of the season, and best results will occur if you allow two seasons to lapse before attempting retreatment. Bait shyness in surviving prairie dogs is common.

Baiting of prairie dogs is only a successful method of control if the bait is readily accepted. Bait is usually not well accepted until early in the fall, when natural forage begins to mature and becomes dry. Use during the early summer (on or after July 1) is only recommended during extremely dry conditions that make the bait more attractive.

Fumigants registered for use on prairie dogs include aluminum phosphide products and a gas cartridge. All aluminum phosphide products are restricted use pesticides. The procedures for use of aluminum phosphide are very time-consuming, and it is generally considered as a follow-up toxicant. The aluminum phosphide pellets or tablets produce hydrogen phosphide gas, which is lethal to all animal life in the treated burrow. For this reason, treatment of burrows should only be done after you have ascertained that non-target wildlife will not be affected. You should be certain that the treated burrow does not harbor other protected species, especially the burrowing owl. To be selective, treat only those burrows you observe one or more prairie dogs enter. Throw 2 to 4 tablets or 10 to 20 pellets down the burrow. Plug the burrow with an inverted sod plug or crumpled newspaper and seal the burrow with tamped soil. The sod or newspaper plug should prevent the soil from covering the pellets or tablets. Proceed to seal all the burrow openings within a 50 foot radius of the treated opening.

Control with aluminum phosphide may also be justified when prairie dogs live close to people. There is some danger in scattering toxic grain where it may be easily accessible to children and farm animals. In addition, prairie dogs that live close to humans are disturbed frequently, which may prevent them from getting a lethal dose of grain in their first feeding. These prairie dogs will easily become bait shy. Another concern is that prairie dogs are host to fleas, which will not be killed by the grain baits. Following a successful grain bait treatment, these fleas will congregate at the burrow opening and will actually cause flea infestations of pets and nearby homes. Since fleas are the common vector of plague, control close to humans in plague areas could temporarily increase the potential for the spread of the disease. Aluminum phosphide has been shown to kill the fleas in the burrows, thus reducing this danger in areas where humans live close to the prairie dogs.

Another fumigant, the gas cartridge, is available from the SDDA, County Weed and Pest Supervisors and the United States Department of Agriculture-Animal and Plant Health Inspection Service-Animal Damage Control (USDA-APHIS-ADC). The gas cartridge is a general use pesticide. Like aluminum phosphide, the label requires consultation with the US FWS prior to using the gas cartridge on prairie dogs. The cartridge must be fitted with a fuse, and the ignited cartridge is placed in the burrow. The burrow is sealed as for aluminum phosphide. Again, because of the cost for the cartridge and the labor involved, the gas cartridge is not recommended for general control. The gas cartridge will not control fleas within the burrow.

The decision to control or not control prairie dogs will remain largely in the hands of the private landowner. Landowners should recognize the role of the prairie dogs in providing habitat for a number of other wildlife species as well as the impacts of expanding populations when making this decision. Reducing prairie dog damage without complete elimination of the prairie dogs is the objective of many landowners. Combining measures in an IPM plan utilizing both approved rodenticides and enhanced grazing practices can provide the relief most landowners need while still providing for ecological, aesthetic and recreational opportunities associated with prairie dogs.

Black-Footed Ferret

The black-footed ferret is a small (22-24 inches overall with a 4-6 inch tail) member of the weasel family that is entirely dependent on prairie dog communities for its shelter and prey. The ferret has a prominent black mask extending across both eyes, black feet and a black tip on its tail. The ferret is listed as an endangered species by both the State of South Dakota and the federal government, and is considered by many to be the rarest mammal in North America. It lives in prairie dog burrows, coming aboveground mostly at night and the early morning hours. Because of its dependence on the prairie dog, it is important to consider the possibility of ferrets when conducting control operations.

Black-footed ferrets may be detected by actual observation at night or in the dawn and dusk hours during the summer and early fall. Tracks may be observed in snow or powdery soil. Characteristic trenches 4 to 6 inches wide, 3 to 4 inches deep and 2 to 3 feet long may be observed where ferrets dig out prairie dogs.

Black-footed ferret surveys may be necessary when conducting control operations with fumigants and zinc phosphate baits. The fumigant and some zinc phosphide labels require the applicator to contact the US Fish and Wildlife Service for information regarding surveys.

Swift Fox and Other Wildlife

The swift fox is a small, tan colored fox living on the prairies of the Great Plains States. The State of South Dakota lists the swift fox as a threatened species. Its current range in the state is very limited, and only three existing populations are known. These occur in and near Badlands National Park and on the Buffalo Gap National Grasslands in Fall River County. Swift fox have also been reported on the Pine Ridge Indian Reservation.

Published reports of research on swift foxes in South Dakota indicate that they are dependent on prairie dog colonies for food and denning sites. However, one known South Dakota population does not appear to utilize these areas. Swift foxes in other states may or may not be associated with prairie dogs.

Swift foxes utilize their dens throughout the year, unlike other wild canids. Swift fox are mostly, if not completely, nocturnal, so observations of foxes in the day are rare. Swift fox dens should be looked for when pre-baiting prairie dog towns. Most fox dens will be located on small hills or high ground near prairie dog towns, although they will often enlarge a prairie dog burrow for a den. Usually the dens have more than one opening and face in an easterly direction. Soil from den excavation is frequently pushed or scattered in a line away for the den and is usually a foot or two wide and three to seven feet long. Food scraps, prairie dog skulls, lower jaw bones, feathers of ground-roosting birds, and miscellaneous animal fur will further help to identify swift fox dens. Scats approximately 1 to 1 1/2 inches long and approximately 3/8 inches in diameter and oval in shape will also be scattered around the den. Usually the scats contain mammal fur and the remains of insects (beetles). If, however, the fox has ingested a lot of bone, the scats will be white and chalky in color and texture. If swift fox dens are located in the control area, the South Dakota Natural Heritage Program (605-773-4229) should be notified immediately to make a determination regarding the safety of the fox. Control of prairie dogs using zinc phosphide will probably not harm the fox; however known dens should be monitored during the treatment to insure that the fox are not affected.