Sarcoptic Mange in American Black Bears in Virginia: An Evaluation of Hair Snare Methodology and an Examination of Factors Influencing Disease Occupancy in the Appalachian Mountains

Abstract

Sarcoptic mange, caused by the mite Sarcoptes scabiei, is an emerging disease that has recently expanded in American black bear (Ursus americanus) populations across the eastern United States. Despite increasing reports of infestation, little is known about how mange influences the effectiveness of noninvasive monitoring techniques or the landscape factors associated with disease occurrence and severity. We evaluated the performance of noninvasive genetic capture-mark-recapture sampling methods in a mange-endemic black bear population while also developing a framework for monitoring and mapping sarcoptic mange using camera trap data collected alongside genetic sampling efforts in the Appalachian Mountains of Virginia. From June–August 2024, we deployed 73 baited hair snare corral traps paired with motion-triggered camera traps across ~930 km² to investigate relationships among mange prevalence, landscape features, bear space use, and sampling success. To evaluate effects of mange on noninvasive genetic monitoring, we compared performance of single-strand and double-strand barbed wire hair corrals, as well as rub trees, for collecting genetic samples using paired camera trap observations to quantify trap use and hair-sample collection success. Bears entered single-strand corrals more frequently than double-strand corrals, though double-strand corrals generally yielded a higher total number of hair samples after the initial sampling weeks. Contrary to predictions, visibly symptomatic bears were not deterred by double-strand corrals and entered corrals at higher rates than non-symptomatic individuals. Hair collection success was positively related to documented corral entries for both corral designs, while rub trees produced no documented bear use. Using the camera trap video data collected concurrently with genetic sampling, we quantified mange prevalence and severity through a standardized visual scoring system and constructed weekly detection histories to model occupancy and detection probability across multiple disease severity thresholds. We recorded 608 unique bear events over 8 weeks, with 19% of detections exhibiting visible signs of mange across 49% of stations. We used occupancy and linear modeling approaches to evaluate influences of landscape, anthropogenic, and climatic covariates on disease occurrence and severity. Occupancy analyses indicated that all bears and non-symptomatic individuals generally avoided developed areas, while symptomatic bears exhibited weaker avoidance of development as disease severity increased. Severe mange was associated with low-elevation valley habitats and flatter terrain, while linear models further indicated that mange severity increased closer to agriculture and forested land cover and farther from open grassland habitats. Detection probability varied with survey week and temperature for non-symptomatic bears but was less influenced by temperature for symptomatic individuals. We further used spatial interpolation and occupancy-based mapping approaches to identify mange hotspots concentrated in the eastern and southern portions of the study area, and overall prevalence declined from 49% to 29% of sites between 2024 and 2025. These findings demonstrate that sarcoptic mange in black bears is spatially structured and influenced by both landscape characteristics and disease severity while also indicating that hair-snare corrals remain effective tools for noninvasive genetic capture mark recapture studies in areas affected by mange. This research provides the first application of camera trap video-based occupancy modeling to evaluate sarcoptic mange dynamics in American black bears and demonstrates that camera trap data integrated with genetic sampling efforts can be used with occupancy, linear, and spatial modeling approaches to monitor and map wildlife disease. These findings provide a framework for adaptive wildlife disease surveillance and offer practical guidance for targeted monitoring and management in regions where sarcoptic mange is present or expanding.