Date of Award
5-2023
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Forestry and Environmental Conservation
Committee Chair/Advisor
Dr. David Jachowski
Committee Member
Dr. Beth Ross
Committee Member
Dr. Cathy Jachowski
Committee Member
Dr. John Kilgo
Abstract
Prey species adjust behaviors in response to various stimuli, responding to both top-down and bottom-up pressures. Large herbivores must attempt to avoid predation either through adjusting behaviors or seeking spatial or temporal refugia, which can scale up to influence individual fitness and ultimately population dynamics. Specifically, predation risk has a great potential to influence ungulate populations by impacting behaviors and survival. Our objective was to quantify ungulate behavioral and population response to a regionally important predator through a case study – white-tailed deer (Odocoileus virginianus) responses to coyotes (Canis latrans) on private lands in the Piedmont of South Carolina at multiple spatial, temporal and behavioral scales. In Chapter 1, we simultaneously examined three deer behaviors: spatial activity patterns, diel activity patterns, and vigilance, and tested for evidence deer modify these behaviors in response to various abiotic and biotic factors including different scales of coyote encounter risk. We found that multiple deer behaviors were responsive to different scales of coyote encounter risk, but behavioral responses varied among demographics. Specifically, does increased vigilance at sites with greater long-term coyote encounter risk, but does’ spatial activity was positively related to short-term coyote encounter risk. Contrary to our predictions, does did not increase vigilance in the presence of juveniles, and does with fawns (nursery groups) did not increase vigilance at sites with greater long-term nor short-term coyote encounter risk. We also found that invasive competitors (wild pigs; Sus scrofa) variably impacted behaviors among deer demographics, potentially increasing risk of does with fawns encountering coyotes. Further, we found that nursery groups were significantly more diurnal compared to bucks and does travelling alone, indicating does with fawns attempt to seek temporal refugia in order to reduce coyote predation risk for their offspring. In Chapter 2, we investigated the effects of deer maternal behaviors and long-term coyote encounter risk on fawn survival. We found that fawn survival was positively related to doe core home range size, but negatively related to the interactive effects of long-term coyote encounter risk and doe-fawn visitation rates. Further, we found that fawn survival was negatively related to the proportion of nocturnal doe-fawn visits. In Chapter 3, we quantified the effects of abiotic and biotic factors on the deer maternal behaviors important to fawn survival. We found that edge density within doe core home ranges was positively related to the size of doe core home ranges and the average distance between doe-fawn pairs. Collectively, these results suggest that habitat conditions impacted maternal behaviors whereas long-term coyote encounter risk did not influence maternal behaviors. In Chapter 4, we developed population models to project population growth rate under current conditions and theoretical scenarios representing specific management actions. We found that the population was gradually declining under current conditions, but even modest increases in fawn survival could stabilize the population. We found that increased availability of alternative coyote food items (and associated reduction in fawn predation) could lead to a stable population, and we showed how managers can likely use a combination of strategies (i.e., reduced doe harvest and increased alternative food for coyotes) to achieve population goals without the need for attempts to eliminate or limit coyote populations. Our study adds to the mounting evidence that coyotes can impact southeastern deer populations, and provide novel insights into how deer are behaviorally responding to coyote predation risk and how those behaviors scale up to population dynamics. Does in our study area likely perceive coyote predation risk and seek temporal refugia for their fawns, yet did not adjust fine-scale maternal behaviors in response to long-term coyote encounter risk. While it is possible that does modify behaviors at other scales, such as birth site selection, our results collectively suggest that does are not exhibiting fine-scale maternal behaviors during the rearing of vulnerable fawns as would be expected based on other studies of ungulates under similarly high levels of predation risk. Further, given population-level declines, our findings collectively suggest deer are not able to modify their behaviors to maximize their reproductive fitness and novel coyotes are outpacing deer in the predator-prey arms race. Fawn survival is paramount to deer population growth in the Southeast, and because coyote predation on fawns likely will remain omnipresent in the region despite any eradication efforts, our study provides important insights into potential ways managers can help sustain and grow deer populations despite coyote presence on the landscape. More broadly, our study highlights the importance of understanding population-specific responses to a novel predator and provides guidance on potential management strategies to increase fawn survival and achieve population goals.
Recommended Citation
Muthersbaugh, Michael, "Drivers of White-Tailed Deer (Odocoileus Virginianus) Behavior, Survival, and Population Growth in the Piedmont of South Carolina" (2023). All Dissertations. 3290.
https://tigerprints.clemson.edu/all_dissertations/3290
Author ORCID Identifier
0000-0002-1508-6092