Angela R. Jarding | Search USGS

USGS2026

Edible baits for systemic flea control, plague mitigation, and wildlife conservation: Evaluation of four active ingredients with three rodent species in western North America

The flea-borne agent of plague, Yersinia pestis , is lethal to endangered black-footed ferrets ( Mustela nigripes , BFFs) and the prairie dogs ( Cynomys spp., PDs) on which BFFs depend for habitat and prey. We developed bait pellets containing insecticides for flea control with PDs. Individual baits contained 0.46, 0.91, 1.21, or 1.52 mg fipronil, 5.40 mg afoxolaner, 50.62 mg fluralaner, or 85.20 mg spinosad. From 2023 to 2025, we tested the baits with black-tailed PDs ( C. ludovicianus , BTPDs), Gunnison's PDs ( C. gunnisoni , GPDs), and Richardson's ground squirrels ( Urocitellus richardsonii , RGSs). We sampled hosts 2810 times and detected 8825 fleas across 2 U.S. States, 1 Canadian Province, 6 sites, 9 PD colonies, and 41 sampling plots. Over ∼12 mo across 5 replicates in South Dakota, USA, bait pellets with 0.91 or 1.52 mg fipronil, applied at a rate of 125 baits/ha, were more effective in reducing the abundance of fleas on BTPDs than 0.46 mg fipronil or the 3 other active ingredients; on 2 South Dakota replicates with data from 24 mo posttreatment, the effects of fipronil pellets on flea abundance had waned after ∼24 mo. Similarly, over ∼12 mo on 2 replicates in Arizona, USA, pellets with 1.52 mg fipronil were more effective in reducing the abundance of fleas on GPDs than pellets with 0.46 mg fipronil; on 1 replicate with available data from ∼2 yr posttreatment, the effects of fipronil pellets had waned after ∼24 mo. Over ∼8-11 mo across 2 replicates in Saskatchewan, Canada, baits with 1.21 mg fipronil/pellet were more effective in suppressing the abundance of fleas on BTPDs and RGSs when applied at 250 pellets/ha than 62 pellets/ha; flea control had waned after ∼20-23 mo. When applied annually at 125-250/ha, baits with 0.84-1.52 mg fipronil (FipBits) provided an effective, efficient, and affordable tool for flea control on PD colonies.

Arizona, Saskatchewan, South Dakota↗

USGS2019

Evaluation of an elk detection probability model in the Black Hills, South Dakota

Since 1993, elk ( Cervus canadensis nelsoni ) abundance in the Black Hills of South Dakota has been estimated using a detection probability model previously developed in Idaho, though it is likely biased because of a failure to account for visibility biases under local conditions. To correct for this bias, we evaluated the current detection probability across the Black Hills during January and February 2009–2011 using radio-collared elk. We used logistic regression to evaluate topographic features, habitat characteristics, and group characteristics relative to their influence on detection probability of elk. Elk detection probability increased with less vegetation cover (%), increased group size, and more snow cover (%); overall detection probability was 0.60 (95% CI 0.52–0.68), with 91 of 152 elk groups detected. Predictive capability of the selected model was excellent (ROC = 0.807), and prediction accuracy ranged from 70.2% to 73.7%. Cross-validation of the selected model with other population estimation methods resulted in comparable estimates. Future applications of our model should be applied cautiously if characteristics of the area (e.g., vegetation cover >50%, snow cover >90%, group sizes >16 elk) differ notably from the range of variability in these factors under which the model was developed.

South Dakota↗