White-tailed deer (Odocoileus virginianus) fawn survival and the influence of landscape characteristics on fawn predation risk in the Southern Appalachian Mountains, USA

PLoS One. 2023 Aug 31;18(8):e0288449. doi: 10.1371/journal.pone.0288449. eCollection 2023.

Abstract

In the Southern Appalachian region of the United States, harvest data has indicated the occurrence of low deer densities while exposing a trend of declining white-tailed deer (Odocoileus virginianus) populations over the past several decades in northern Georgia. A triumvirate of increasing fawn predator populations reside in the Southern Appalachian Mountains including coyotes (Canis latrans), black bears (Ursus americanus) and bobcats (Lynx rufus). This region is also characterized by a homogenous landscape composed of mature forests and sparse understory vegetation, likely lacking adequate cover to offer fawns refugia from predators. Our objectives were to estimate survival and cause-specific mortality rates of fawns while assessing a possible link between mortality risk, intrinsic fawn characteristics (i.e., birth mass, Julian birth date, sibling status), and landscape features within fawn usage areas. During 2018-2020, we radio-collared 71 fawns within the Chattahoochee National Forest of northern Georgia, USA and monitored survival to 12 weeks of age. We observed low fawn survival (cumulative = 0.157, 95% CI = 0.091-0.273; vaginal implant transmitter = 0.196, 95% CI = 0.096-0.403) with predation as the leading cause of all known mortalities (45 of 55 mortalities; 82%) due primarily to coyotes (n = 22), black bears (n = 12), and bobcats (n = 7). Relationships between landscape features and fawn predation risk were minimal with only one informative covariate. Increasing amounts of early successional land cover within fawn usage areas decreased fawn mortality risk within the first 20 days of life, but elevated mortality risk thereafter. All fawns with any amount of early successional land cover in their usage areas died of predation (n = 13) at various time intervals, suggesting limited areas of potential fawning cover may be targeted by predators. However, fawn predation risk seemed to be high regardless of landscape covariates due to the limited number of surviving fawns. Coyote-caused mortality occurred over a longer period at a consistently higher magnitude than all other forms of mortality, indicating possible delayed prey-switching behavior and coyote predation as an important factor of fawn survival. The low recruitment of fawns influenced by high predation rates and homogenous habitat conditions is likely the cause of deer population declines in the region.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Appalachian Region
  • Coyotes*
  • Deer*
  • Female
  • Grasshoppers*
  • Lynx*
  • Predatory Behavior
  • Ursidae*

Supplementary concepts

  • Odocoileus virginianus

Grants and funding

This study was primarily funded by the Georgia Department of Natural Resources through Grant GA-W-F17AF00741 to GJD and KVM. Research was also supported by the U.S. Department of Agriculture National Institute of Food and Agriculture, McIntire Stennis Capacity Grant (Project 1020089) to GJD. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.