Figure 1. Black-tailed Prairie Dog.
About Prairie Dogs
Prairie dogs are highly social animals belonging to the squirrel family. There are five species of prairie dogs in North America. It is the black-tailed prairie dog with its tan color and short black tipped tail, that resides in South Dakota.
Role in Grasslands: Prairie dogs are an important component of the grassland ecosystem, providing habitat to numerous plant and animal species. They feed on grasses and forbs as well as seeds and some insects. They can consume or damage large amounts of vegetation and become a problem for livestock producers when they compete with livestock for forage. Dry conditions can aggravate this issue.
Behavior: It is important when managing any pest to know their life patterns. The black-tailed prairie dog is active during the day. They do not hibernate but do remain below ground during extremely cold periods. Their “towns” consist of an elaborate system of burrows that can go up to 10 feet deep and 100 feet in length. There can be 50 to 100 burrows per acre. The burrow openings have mounds of dirt ½ to 1-foot-high at the entrance. These serve as lookout stations so the prairie dogs can watch for impending danger. The black-tailed prairie dog breeds in late January and February and gestation period is 4-5 weeks. The babies are born underground in March and remain there for 6 weeks.
There are a number of control measures available to landowners to help alleviate damage from serious prairie dog infestations.
- Biological Controls: Biological controls include practices that provide habitat for predators such as raptors, snakes, badgers and ferrets can be part of a long-term control plan. In some areas raptor perches are installed to encourage birds of prey to roost and key on the prairie dogs for food. Diseases have also been known to reduce prairie dog populations. At times in the past, South Dakota has experienced large prairie dog die offs from sylvatic plague in south west areas of the state. However, it is also important to note that sylvatic plague can be transmitted to humans and is therefore also a human health concern.
- Cultural Controls: Another management tactic is the use of cultural controls. Prairie dogs do not like tall grass. Range management techniques that keep grass stands healthy, can deter prairie dog settlement and colony expansion. Location and distribution of watering facilities, salt licks, and other factors that tend to concentrate livestock should be managed to avoid overgrazing.
- Mechanical Controls: Mechanical controls include hunting and trapping prairie dogs to help reduce numbers. However, it is recognized that shooting is not effective in reducing prairie dog numbers in heavily infested areas. The prairie dogs, hearing the sound of gunfire, will hide underground, leaving little for hunters to aim for. Trapping can be expensive and time consuming. Mechanical controls by themselves can work to keep small infestations from expanding but they are seldom effective on more serious infestations.
The above management techniques can be used together to provide an integrated, multi-pronged approach to help reduce prairie dog infestations. However, with serious prairie dog infestations, the use of chemical controls may need to be considered.
There are four products labelled in South Dakota to control prairie dogs. These include zinc phosphide, chlorophacinone, aluminum phosphide, and gas cartridges.
Treated Grain Baits
Two of the products, zinc phosphate and chlorophacinone, are treated grain baits.
- Zinc Phosphide: The first, zinc phosphide, is a slow acting toxicant that is most effective when green grass becomes dry and dormant and prairie dogs are looking for other sources of food. For this reason, this product is only registered for use between July 1st and January 31st in South Dakota. In addition, the prairie dogs are often hesitant to consume this product because the zinc phosphide has a prominent garlicy odor. Therefore prior to using the baited oats, the label requires that the burrows first be prebaited with good quality oats. This helps the prairie dogs to accept the oats as food. Applicators should prebait every hole or burrow in the town. One heaping teaspoon of the grain should be sprinkled thinly around the outer edge of the mounds. Once prebaiting is complete, applicators need to leave the area and not return for 3-4 days. After this period, a check should be done to see if the untreated grain was eaten. If it was consumed, then the treated oats can be applied to burrows using the same technique as with the prebait. However, when applying the treated oats, applicators should be wearing protective equipment and rubber gloves as small amounts of zinc phosphide can be absorbed through the skin. Applying this product to wet ground or when rain or heavy dew is expected is not recommended as moisture reduces the effectiveness of the product.
- Chlorophacinone (Rozol): The second treated grain product is chlorophacinone (Rozol). Chlorophacinone is an anti-coagulant that also results in death when prairie dogs or other animals ingest it. Since chlorophacinone treated grain does not have the same strong odor as the zinc phosphide treated grain it does not require prebaiting and it can be applied more than once per season. It can also be used to clean up small areas that were missed with zinc phosphide treatments. This product can maintain toxicity for a long period of time, therefore, the label requires that the bait be placed at least 6 inches below ground down the prairie dog burrows. Areas treated with chlorophacinone need to be scouted for carcasses 4 days after the treatment, and periodically thereafter as specified on the label, as carcasses can pose a threat of secondary poisonings. Carcasses and any chlorophacinone found above ground should be collected and buried at least 18 inches below ground. Chlorophacinone is labelled for use in South Dakota between October 1st and March 15th.
|Figure 2. Correct way to apply baited grain around burrow openings.||Figure 3. Incorrect way to apply baited grain around burrow openings.|
The other two products labelled for prairie dog control are Aluminum phosphide pellets or tablets and gas cartridges. These products are placed below ground and both form gasses that are toxic to the animals in the burrows.
- Aluminum Phosphide Pellets: The aluminum phosphide pellets or tablets form phosphine gas when they come into contact with water. When handling this product, cotton gloves and long sleeves are recommended. Aluminum phosphide is a fumigant and therefore applicators are required to fill out a detailed fumigation management plan prior to application of this product. Fumigation management plans can be downloaded from the SD Department of Ag website.
- Gas Cartridges: The gas cartridges have a fuse that is lit. The cartridge is then placed in the burrow where it releases carbon monoxide, sodium nitrate or sulphurous gases. When using aluminum phosphide or gas cartridges, burrow openings should be plugged on the burrow where the treatment was placed and the surrounding burrows. Newspaper or a paper plate can be placed over the opening, and dirt placed on top to seal the opening. Some sources recommend stuffing newspaper, or seed/feed bags down the burrows as it makes it difficult for the prairie dogs to escape. Both aluminum phosphide and gas cartridges can be costly and labor intensive to use. They are recommended for use to clean up small infestations.
All products used to treat prairie dogs are dangerous to animals and humans. Precautions should be taken to protect non target animals. Zinc phosphide, chlorophacinone and aluminum phosphide are all restricted use pesticides. To purchase and apply restricted use pesticides or apply general use pesticides to rangeland in South Dakota, individuals must be certified as pesticide applicators. Anyone handling these products should read and follow label directions.
- Huber, Sandy and Wilson, Jim. 2008 Prairie Dog Management in South Dakota. ExEx8163
- Vantassel, Stephen. Prairie Dog Management. Montana Dept. of Agriculture
- Pugh, Tim. 2015. Prairie Dog Management. Applicator Recertification Training, 2015.