The Utah Prairie Dog (UPD) Revised Recovery Plan sets forth recovery goals while addressing species threats and prescribing mitigation measures (U.S. Fish and Wildlife Service 2012). Recovery efforts for this species have contributed to a positive long-term trend in Utah prairie dog (Cynomys parvidens) numbers, yet sylvatic plague remains among the most pressing threats to UPD populations (U.S. Fish and Wildlife Service 2012). Plague can cause local extirpations of UPDs; it can also shrink and/or cause fluctuations in colony sizes and it can cause colonies to become further apart from one another (Cully and Williams 2001; U.S. Fish and Wildlife Service 2012). Current efforts to manage plague are to treat UPD burrows with deltamethrin dust to suppress flea numbers and decrease the probability of plague transmission. A recent retrospective analysis of UPD counts showed dusting burrows with deltamethrin increases colony growth and persistence (Larsen et al. 2022). However, dusting with deltamethrin can be extremely time-consuming to implement and fleas may eventually build up a tolerance to deltamethrin, which could make it ineffective at treating plague. State and federal wildlife and land management agencies need alternative plague prevention treatments for UPDs that are more efficient as time and budget constraints continue to increase and can provide an alternative if deltamethrin becomes less effective over time. A potential replacement or compliment to deltamethrin treatment is fipronil, an insecticide commonly used to treat domestic pets for flea control. Prairie dogs ingest the fipronil in bait pellets (FipBits) that are distributed at the research sites. Studies for the use of fipronil as a systemic flea control agent are under way for Gunnison's (AZ) and black-tailed (SD and MT) prairie dogs, with promising initial results. In addition, researchers are also working to acquire a study site with white-tailed prairie dogs for FipBit studies to understand if efficacy differs among the four (4) prairie dog species located in the United States (R. Matchett, U.S. Fish and Wildlife Service, personal communication). The Bureau of Land Management (BLM), U.S. Forest Service (USFS), and National Park Service (NPS) currently conduct most of the flea control efforts for UPDs. Presently, these agencies apply deltamethrin on lands under their management. The application of deltamethrin requires a considerable expenditure of personnel time. This proposal aims to contribute to research that may develop a more efficient and effective way to control plague in UPDs on federal/state land and conservation properties. Previous research estimates that FipBits can reduce the cost of flea control for prairie dogs by 90% (Eads et al. 2021). This project would be working only with UPDs, but researchers would collaborate with other researchers studying FipBit use in other species of prairie dogs. This project is contingent upon Randy Matchett from the U.S. Fish and Wildlife Service (USFWS) working with the U.S. Food and Drug Administration (FDA) to ensure that FipBits, which will be considered a drug, are following all rules and regulations required.

The goal of the UPD program is conservation and recovery of UPDs, which will ultimately lead to delisting of the species. The specific objective of this proposal is to conduct research into an efficient and effective method for controlling fleas and plague transmission in UPD. If successful, FipBits will be available for use on UPD colonies on conservation easements, state-owned wildlife management areas, and public lands. The primary objective is to evaluate if FipBits can provide effective control of fleas in UPD colonies, thereby reducing the probability of epizootic plague events in those colonies. Having a second tool in the flea/plague control toolbox will also decrease current concerns of fleas developing resistance to deltamethrin.

Failing to come up with new sylvatic plague treatment options could lead to collapses of large colonies, as well as decline in the species overall. Current plague treatment options can be expensive and time consuming, and sometimes are not implemented on a large scale due to these constraints. No ill effects for prairie dogs in field applications of fipronil grain or FipBits have been observed since experimentation with fipronil baits began in 2016. Better prairie dog reproduction and greater prairie dog body condition on plots treated with fipronil has been observed (Eads et al. 2022, Eads et al. 2021). No ill effects for small mammals have been observed with field applications of fipronil grain, but there are indications of short-term negative effects of FipBits (decreased survival and abundance, as observed with deltamethrin; unpublished data). Similarly, offering a FipBit to deer mice in captivity has resulted in toxicity issues that were not unexpected (unpublished data). There will be a small mammal trapping element to this study of FipBits to help determine potential impacts to small mammals that FipBits may have. FipBits may impact small mammals because they were designed to adequately dose a ~1,000 g prairie dog for flea control. A 21 g mouse consuming the same FipBit would be dosed at ~40% of the LD50 for laboratory rats and mice. Preliminary assessments of FipBit disappearance rates, following the recommended treatment protocols, indicates the vast majority of FipBits are consumed by prairie dogs during the first day when baits are distributed at dawn, minimizing availability to small mammals during the first night after treatment. During a field trial in 2022, 77% of FipBits placed on prairie dog burrows in the morning were gone within 10 hours, and more than 90% disappeared within 30 hours. There is also some evidence that deer mice may have a taste aversion for FipBits, so that might help reduce their consumption. David Eads and colleagues (unpublished data) have been conducting feces exposure trials with tiger salamanders and dung beetles from prairie dogs that consumed fipronil-laced bait and has found minimal to no effects. Last year, they monitored grasshoppers on fipronil treated sites in South Dakota and detected no ill effects. The collaborative group has also evaluated potential effects of fipronil grain treatments on non-target arthropods (pit-fall traps) in South Dakota and the results suggest minimal to no effects of the fipronil treatments on the abundance of several arthropod families/species. From captive feeding studies, there have been multiple tissue assay results of fipronil and fipronil sulfone (the mammal metabolite) indicating fairly rapid elimination in prairie dogs over 30-45 days post-feeding (primarily in feces). The highest levels are seen within 5-6 days of consuming FipBits and decline thereafter. Such rapid elimination rates and declining levels in prairie dogs would suggest a narrow window for exposure to predators of prairie dogs. To investigate effects of black-footed ferrets (Mustela nigripes) consuming prairie dogs that consumed FipBits (and for insights to other prairie dog predators), carcasses from prairie dogs that consumed FipBits were fed to 6 geriatric black-footed ferrets in captivity for 30 days with no ill effects observed. The carcasses were fed in a way to simulate expected field conditions with declining levels of fipronil residues over time from prairie dogs that were euthanized at 1, 3, 5, 10, 20, and 30 days post-FipBit consumption. Prairie dog tissues (heart, lung, liver, kidney, brain, muscle, fat) were tested for fipronil and fipronil sulfone concentrations so they could estimate how much fipronil residues black-footed ferrets consumed. All of the data so far indicates that FipBits are a safe and effective flea control tool based on studies conducted over the last four years. Continued evaluations and experimentation and will help researchers as much as possible to refine FipBit treatments and evaluate new bait pellets with different active ingredients to rotate in an integrated pest management system to minimize fleas developing resistance to any one active ingredient and win the battle against sylvatic plague.

All activities in this proposal are done in support of the Utah Prairie Dog Revised Recovery Plan. The applicable objectives of the recovery plan are to establish and maintain viable Utah prairie dog populations in each Recovery Unit. To achieve this objective, management strategies need to be in place to prevent and respond to threats from disease. The Division coordinates plague abatement activities with other public land entities (BLM, USFS), as well as participates in ongoing research into plague dynamics.

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All aspects of the Utah prairie dog recovery program maintain compliance with ESA standards. When applicable, NEPA and cultural resources surveys are conducted as required, primarily by the federal land management agencies.

The Utah Prairie Dog Recovery Biologist will coordinate with the USFWS, U.S. Geological Survey, and Turner Endangered Species Fund to perform field evaluations of FipBits to prevent epizootic plague. The Division will conduct this evaluation via a collaborative effort working with wildlife conservation partners, including the BLM, USFS, and Utah School and Institutional Trust Lands Administration (SITLA). The large-scale research plan for FipBits is to establish at least 40 experimental pairs of prairie dog plots/colonies, on at least 10 sites across the West, where one member of each pair is treated with FipBits and the other member is not treated with any plague mitigation tools as a baseline. Researchers have already established sites for Gunnison's and black-tailed prairie dogs and are anticipating including white-tailed and Utah prairie dogs in the study shortly (Eads et al. 2021; R. Matchett, U.S. Fish and Wildlife Service, personal communication). Prairie dogs ingest fipronil from 1.34-gram bait pellets FipBits that each contain 0.84 mg of fipronil (Eads et al. 2021). Researchers spread out and distribute the baits across the landscape at 50 baits per acre, which is one (1) pellet every 30 feet in a grid pattern. Researchers distribute FipBits from ATVs at approximately 50 acres per hour. Researchers currently consider FipBits effective for 1-2 years between applications (Eads et al. 2021). The best available locations for the research were determined from the 2023 UPD spring counts. Ideally, the research sites have colonies that have 25 acres of occupied UPD habitat and that have not had deltamethrin dust applied in the previous 2 years. In addition, site selection will require that the study take place on protected or SITLA land, and selected sites should have a high expectation of frequent plague epizootics (Eads et al. 2021; R. Matchett, U.S. Fish and Wildlife Service, personal communication). Technicians and researchers will perform flea swabs on the burrows to obtain baseline information on flea levels present on/in the burrows at the sites. Researchers will obtain and analyze additional baseline data, including burrow density and estimated number of individuals on each site. Researchers will also aim trap 30 UPDs on each of the sites to obtain baseline information on flea levels present on the prairie dogs themselves, particularly focusing on the number of fleas found on each individual. Researchers will anesthetize the trapped UPDs with isoflurane and will sex, weigh, measure hind foot length, assign body condition score, ear tag, and comb for fleas with a 89X51 mm fine-tooth comb for 30 seconds for each individual (Eads et al. 2021). Researchers will distribute the FipBits on the landscape after all of the baseline data has been collected. Technicians will use ATVs to dispense the FipBits at a density of 50 baits per acre at all study sites that are receiving the treatment. Technicians will use triple-shooters to dispense the FipBits from the ATVs at the desired density (R. Matchett, U.S. Fish and Wildlife Service, personal communication). Based on time available and recommendations from experts, technicians may drive ATVs through untreated sites and release bait that does not contain fipronil in order to mitigate any effect that the bait may cause.

Researchers will conduct additional follow-up analysis, including counting individuals on the sites consistently; ideally, sites will be counted at least once per month during the active season for UPDs. Researchers will regularly monitor the site for any potential negative impacts, including deceased UPDs. Researchers will perform the same flea analysis, including burrow swabs and UPD trapping and biological monitoring as frequently as time and budget will allow post-treatment to help determine how long treatments remain effective (R. Matchett, U.S. Fish and Wildlife Service, personal communication). The study site colonies will also have regular Utah prairie dog annual spring counts conducted yearly.

U.S. Fish and Wildlife Service, Bureau of Land Management, U.S. Forest Service, National Park Service, U.S. Geological Survey, Utah Department of Natural Resources, Iron County, Garfield County, and the Tuner Endangered Species Fund. The Utah Prairie Dog Recovery Team supports this proposed project.

Implementation of this project may result in a superior flea control treatment for UPDs. FipBits will require significantly less personnel time and may be more effective than currently employed methods. Distribution of a more efficient and inexpensive flea control treatment across protected land (federal land and conservation properties) will allow for an increase in treatment area. More effective and predictable flea control will result in increased UPD numbers, which will help UPDs get closer to the UPD Revised Recovery Plan goals of 1,000 spring counted adult individuals on protected land in each of the three recovery units for 5 consecutive years. Achieving the Recovery Plan goals may to a species status review, and potential delisting and post-delisting management for the species.

The Bureau of Land Management and the U.S. Forest Service are multi-use agencies and have grazing allotments on many of the Utah prairie dog colonies on federal land. Grazing considerations will be discussed during site selection for this study.