Changes to Health Parameters of White-Tailed Deer during a Drought in the US Virgin Islands

Abstract

Resident white-tailed deer (Odocoileus virginianus) on St. John, US Virgin Islands offer a unique case study for understanding a population under pressure from climate change. During a 2015–2016 regional drought, deer health parameters including body condition, coat condition, tick prevalence, musculature, and stress hormones were tracked over three field seasons representing the onset, peak, and recovery phases of the drought. All health indicators showed significant change over the course of the drought, and post-hoc tests suggest some indicators (body condition, musculature, and ticks) were more sensitive during drought onset. High levels of cortisol during the peak period indicated substantial stress to the population, which normalized during recovery. The strongest correlations were between overall health/body condition and musculature and overall health/body condition and coat condition. The weakest correlations were between ticks and the remaining three variables. These results support the hypothesis that various measures of deer health are related. The frequency and intensity of droughts and environmental stressors are predicted to increase in the future due to climate change, which will further challenge this island deer population.