White-tailed deer behaviors at three forage settings: Implications for transmission of chronic wasting disease

Abstract

Chronic wasting disease (CWD) is induced by a protein found in cervid brains called prions that cause folding of other neural proteins. These prions are transmitted among individual cervids via direct (individual to individual), indirect (e.g., individual to environment), and self (e.g., licking an infected area) contacts. Supplemental feeding tends to concentrate deer (Odocoileus spp.), with implications for inter-individual prion transmission. Prion transmission depends on deer behaviors, yet information on behaviors at various forage settings is lacking. We quantified behaviors thought to play a role in prion transmission exhibited by white-tailed deer (O. virginianus) at baited sites, food plots, and areas used for foraging in the surrounding landscape (hereafter landscape forage areas [LFAs]) using camera trapping and road-based transect surveys during the post-breeding period (January through April 2021–2023). We conducted 4,172 deer observations across all forage settings (15% from LFA transects, 69% from bait sites, 16% from food plots), and found fewer direct contacts (i.e., deer to deer) at food plots and LFAs compared to bait sites. We found a lower number of self-contacts (e.g., deer licking a body part) at food plots compared to bait sites and observed fewer environmental contacts (e.g., deer potentially ingesting soil) at food plots and LFAs compared to bait sites. At bait sites, we found that yearling males had a greater tendency to directly contact male and female adults, with this tendency greatest when >2 adults were visible. We also measured deer fecal deposition at forage settings, as prions in feces are potentially available for uptake by uninfected individuals. The probability of finding a deer fecal pellet at food plots and LFAs was lower than at bait sites, but amount of fecal material did not vary among forage settings. Ordinal day negatively affected the probability of finding a deer pellet across all forage settings. Our findings indicate that the probability of direct and environmental contacts at bait sites exceeds contacts at food plots and LFAs. Additionally, higher probability of fecal deposition coupled with more environmental contacts at bait sites increases potential transmission of prions. In areas of concern for CWD, food plots and LFAs appear to offer less risky food sources for deer during the post-breeding period compared to bait sites.