Effects of fipronil bait pellets on two cricetid species: Potential implications for plague mitigation and wildlife conservation

David A. Eads; Marc R. Matchett; Travis M. Livieri; Richard A. Bowen; Airn E. Hartwig; Stephanie Porter; Mary L. Wright; Jason Fly; Madisen Hartlaub; Phillip Dobesh; Paul Roghair; Eddie Childers; John P. Hughes; Michelle L. Hladik; Gregory P. Dooley; Brian J. Smith; Rachel A. LaCasse; Kristy Bly; Dean E. Biggins

doi:10.1016/j.ijppaw.2026.101239

Effects of fipronil bait pellets on two cricetid species: Potential implications for plague mitigation and wildlife conservation

International Journal for Parasitology: Parasites and Wildlife

By: David A. Eads, Marc R. Matchett, Travis M. Livieri, Richard A. Bowen, Airn E. Hartwig, Stephanie Porter, Mary L. Wright, Jason Fly, Madisen Hartlaub, Phillip Dobesh, Paul Roghair, Eddie Childers, John P. Hughes, Michelle L. Hladik, Gregory P. Dooley, Brian J. Smith, Rachel A. LaCasse, Kristy Bly, and Dean E. Biggins

https://doi.org/10.1016/j.ijppaw.2026.101239

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Abstract

We evaluated the effects of fipronil bait pellets on two cricetids that commonly occupy colonies of black-tailed prairie dogs (Cynomys ludovicianus; BTPDs): western deer mice (Peromyscus sonoriensis) and northern grasshopper mice (Onychomys leucogaster). In one experiment, bait pellets (0.96 mg fipronil/bait) were applied at 75 baits/ha to three 1.44-ha plots on a BTPD colony. Mouse abundance declined by 70% from before to 6-10 d after treatment. In a second experiment, bait pellets (0.46 or 1.52 mg fipronil/bait) were applied at 125 baits/ha to four plots (0.85-1.86 ha) on two BTPD colonies; two non-treated plots were baselines (1.09 and 2.06 ha). From before to 11-15 d after treatment, mouse abundance declined by 51%- 67% on the treated plots vs. a decline of 9% on the non-treated plots. Mouse survival from before to 11-15 d after treatment was 51% lower on the treated plots. In a third experiment, bait pellets (0.84 mg fipronil/bait) were applied at 125 baits/acre on two 1.44-ha plots on a BTPD colony; two 1.44-ha non-treated plots were baselines. Mouse survival from before to 30-44 d after treatment was 45% lower on the treated plots; the abundance of deer mice on the treated plots remained similar from before to 30-44 d after treatment, perhaps due to juvenile recruitment and/or immigration. In a laboratory experiment, 33 deer mice offered one bait pellet (0.86 mg fipronil/bait) consumed 27% of their bait, on average (range = 0-100%). Over 3 d, deer mouse mortality was estimated at 53%; mortality increased with fipronil dose, which averaged 11 mg fipronil/kg body mass (range = 3-46 mg/kg). Brain samples were available from 31 deer mice; all tested positive for fipronil sulfone, the primary mammalian metabolite of fipronil, at 19 to 61,205 ng fipronil sulfone/g. Additional experiments could determine if these findings scale up to larger landscapes.

Suggested Citation

Eads, D., Matchett, M.R., Livieri, T.M., Bowen, R.A., Hartwig, A.E., Porter, S., Wright, M.L., Fly, J., Hartlaub, M., Dobesh, P., Roghair, P., Childers, E., Hughes, J.P., Hladik, M.L., Dooley, G.P., Smith, B.J., LaCasse, R.A., Bly, K., and Biggins, D.E., 2026, Effects of fipronil bait pellets on two cricetid species: Potential implications for plague mitigation and wildlife conservation: International Journal for Parasitology: Parasites and Wildlife, v. 30, 101239, 8 p., https://doi.org/10.1016/j.ijppaw.2026.101239.

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Additional publication details
Publication type	Article
Publication Subtype	Journal Article
Title	Effects of fipronil bait pellets on two cricetid species: Potential implications for plague mitigation and wildlife conservation
Series title	International Journal for Parasitology: Parasites and Wildlife
DOI	10.1016/j.ijppaw.2026.101239
Volume	30
Year Published	2026
Language	English
Publisher	Elsevier
Contributing office(s)	California Water Science Center
Description	101239, 8 p.
Country	United States
State	South Dakota
Other Geospatial	Badlands National Park, Buffalo Gap National Grassland, Conata Basin