9th International Deer Biology Congress

AUTHORS: David B. Stone, Bradley S. Cohen, James A. Martin, Thomas J. Prebyl – Warnell School of Forestry and Natural Resources, University of Georgia; Charlie Killmaster, Georgia Department of Natural Resources, Wildlife Resources Division; Karl V. Miller, Warnell School of Forestry and Natural Resources, University of Georgia

ABSTRACT: Individuals may reduce competition by temporally or spatially partitioning their use of a shared resource [1,2]. Temporal resource partitioning, in particular, can be vital to the coexistence of species, or reduce competition among conspecifics, that share a common resource [2]. Sex-specific behavioral differences in ungulate resource use increases segregation as individuals attempt to avoid antagonistic interactions [3]. However, interference competition from dominant cohorts may reduce subordinates’ access to food resources, regardless of sex [4,5,6]. We hypothesized that white-tailed deer (Odocoileus virginianus) temporally segregated at supplemental feeding sites based on social rank and that segregation was affected by phase of the breeding season (pre-breed, breed, and post-breed) and diel cycle (diurnal or nocturnal hours). If cohorts do segregate temporally, we predicted that the resulting activity patterns would manifest in one cohort being relatively more susceptible to hunter-induced mortality. We used camera traps to record the presence of each cohort at feeding sites. To quantify temporal segregation, we used multi-state modeling to determine the probabilities for feeding sites (n = 16) to transition from 1 of 4 states (1-no deer present, 2-subordinate cohort present, 3-dominant cohort present, 4- both subordinate and dominant cohort present) to a different state. Additionally, we calculated the probability that a feeding site was in a particular state during diurnal and nocturnal hours during the 3 phases of the breeding season. We determined that transition probabilities differed by season and diel cycle and dominant and subordinate cohorts clearly avoided each other at the feeding sites. During the pre-breeding season, the probability of a subordinate being present during diurnal hours was 3.0x more likely than a dominant being present, but did not differ during nocturnal hours (Fig. 1). There was no difference for dominants and subordinates during diurnal or nocturnal hours during the breeding season (Fig. 1). In the post-breeding season, subordinates were 1.7x more likely to be at the feeding site than a dominant during diurnal hours but cohorts did not differ during nocturnal hours (Fig. 1). Our study illustrates how patterns in temporal resource partitioning at feeding sites may influence relative risk to different sources of mortality. Subordinates used the shared resource at similar rates, but the pattern of temporal partitioning evidently would make subordinates more susceptible to human predation.