Black-tailed prairie dog (Cynomys ludovicianus)
Gunnison’s prairie dog (Cynomys gunnisoni)
Magnus McCaffery, Levi Fettig
Vermejo Park Ranch, NM
Bad River Ranches, SD
Z-Bar Ranch, KS
The range-wide decline of all prairie dog species is attributable to non-native disease—sylvatic plague (Yersinia pestis); loss of habitat and habitat fragmentation; and human persecution (e.g. poisoning and shooting).
Both the black-tailed and Gunnison’s prairie dogs have been candidate species for listing under the Endangered Species Act. Neither species is currently listed nor afforded any significant state protection in New Mexico, South Dakota or Kansas.
Prairie dogs are a keystone species whose presence on the landscape has a profound positive effect on biodiversity. The primary goal of TESF’s prairie dog restoration project is to provide sufficient habitat to support a stable population of black-footed ferrets. Black-footed ferrets are an endangered obligate predator of prairie dogs that require large, disease-free prairie dog complexes in order to survive.
- The long-term objective for Gunnison’s at Vermejo is to establish a 3,000 – 5,000-acre complex in the mountain meadows surrounding Castle Rock and Bremmer Park. In the short-term, once Gunnison’s have reoccupied >2,000 acres in the complex, we will begin plague mitigation efforts (sylvatic plague vaccine, FipBits, or similar products) and release ferrets.
- At Bad River we will increase the coverage of the ACRA colonies to 3,000 – 5,000 acres using one of the plague mitigation tools listed above.
- At the Z Bar we will continue to investigate methods to increase colony coverage to 1,000 acres, at which time we will release ferrets.
Supporting Rationale for Objective
Prairie dogs are exquisitely sensitive to plague and the disease is the primary conservation concern at most black-footed ferret restoration sites including Vermejo and Bad River. Until recently, the only way to mitigate plague was to dust prairie dog burrows with a pulicide to kill fleas, which serve as the vector for the disease. This method of plague control is expensive and labor intensive but generally effective; however, there have been instances where colonies have succumbed to plague after having been dusted (e.g., Bad River in 2012) and recent studies suggest that in long dusted areas (>8 years) fleas have begun to develop resistance to the pulicide.
Recently, federal and state agencies, and NGOs have investigated two additional approaches to plague mitigation. The first is a sylvatic plague vaccine (SPV), which is delivered to prairie dogs through small bait pellets (i.e., prairie dogs that eat the bait pellets are vaccinated against plague.) The second plague mitigation tool in development, dubbed “FibBit,” uses the same bait matrix as the SPV but with fipronil – a common insecticide applied to pets – as the active ingredient. Prairie dogs that consume a FipBit bait receive a small dose of fipronil which kills the fleas that serve as the vector for the disease.
At Vermejo and Bad River prairie dog restoration efforts hinge on finding an affordable and efficacious tool to mitigate plague. At the Z Bar, where robust vegetative growth often dampens colony growth, we will investigate the use of fire and seasonal bison grazing to stimulate colony growth.
Few species engender as much controversy in the American West as prairie dogs. Many agricultural producers view prairie dogs as competitors for a limited grass resource whose presence represents an immediate threat to their livelihood; conservationists view prairie dogs as a keystone species whose presence on the landscape meets the very specific habitat requirements of numerous imperiled species. TESF seeks to find a balance where prairie dogs and associated ecological processes and species assemblages can exist in harmony with for-profit endeavors (e.g., bison ranching and big game hunting).
Currently, prairie dogs throughout the American West occupy ~3% of their historical range. This significant loss was largely due to poisoning campaigns in the early and mid-20th century. More recently, the introduced disease sylvatic plague has been the primary range-wide conservation challenge.
Prairie dog restoration on Turner properties began in 1997 with the development of a reliable prairie dog soft-release technique. Using this method, TESF expanded black-tailed prairie dog acreage on the Vermejo Park Ranch in New Mexico from 500 to 10,000 acres; the Ash Creek Restoration Area (ACRA) of Bad Rivers Ranches in South Dakota from 125 to 1,800 acres; and the Z-Bar in Kansas from 75 to 590 acres. Using the same translocation technique, the Gunnison’s prairie dog population at Vermejo has increased from 23 to 3,900 acres. In total, prairie dog acreage on Turner properties of which TESF has had oversight grew from 725 to a maximum of 16,290 acres.
Project Activities in 2018
In 2018, the black-tailed prairie dog populations at Z Bar and Vermejo Park remained fairly stable at ~ 420 and ~10,000 acres, respectively, while Gunnison’s at Vermejo increased slightly to cover ~1,000 acres. The black-tailed prairie dog population in ACRA, which continues to struggle with plague, ended the year at ~ 300 acres scattered over four colonies.
In early 2017, the black-tailed prairie dog complex in ACRA covered ~ 1,800 acres and supported an estimated 22,000 prairie dogs. At that same time, TESF and four other ferret release sites secured a NFWF grant to implement field testing of SPV at the landscape level (> 500 acres.) This landscape level treatment was predicted to be the last step in a 10-year process of refining the distribution and licensing of the product. Unfortunately, and for reasons which remain unclear at this time, in 2018 the SPV failed at two of the five sites, including in ACRA, resulting in significant losses of prairie dogs at those locations.
Prairie dog colonies on the Z Bar covered 420 acres in late 2018, a loss of 29 acres from 2017. The largest Z Bar colony, which has been subjected to growing season grazing, grew 4% in 2018. Results from our fertilizer-grazing study suggest that applying fertilizer to the perimeter of colonies to encourage bison grazing in those areas is not an effective method to stimulate colony expansion. What was effective in stimulating colony growth and what accounts for the 4% growth on the largest colony in 2018, was a prescribed burn followed by bison grazing on the perimeter of that colony.
Proposed Future Activities and Considerations
The future of prairie dog populations at Vermejo and Bad River rests solely on the efficacy and affordability of plague mitigation. Based on the results of 2017-2018’s SPV application in ACRA, there are questions regarding the vaccine’s efficacy which, in combination with the costs (estimated to be $25/acre/year), leaves us uncertain whether SPV is a viable option for future plague mitigation on Turner properties. What does look promising for Turner prairie dogs are the results from recent FipBit trials in MT and AZ. Preliminary data suggests flea loads are reduced to <1 flea/prairie dog within 9 months of application. Additionally, the cost of FipBits is predicted to be less than $1/acre/year.
In 2019, we will continue to investigate the use of prescribed fire and bison grazing to stimulate colony expansion at the Z Bar. If conditions are suitable, we will burn ~100 acres along the perimeter of the largest colony, allow bison to graze the recently burned area, and measure the colony growth in response to these two treatments.