Alpine thermal dynamics and associated constraints on the behavior of mountain goats in Southeast Alaska

Abstract

Alpine Caprinae, including mountain goats (Oreamnos americanus), have been described to be sensitive to temperature changes within their summer range and consequently may be forced to select habitats that allow for the maintenance of a stable core temperature on warm days. Survival may be inhibited if warm ambient temperatures cause mountain goats to reduce time foraging or if too much time is spent on thermoregulatory habitat selection. I investigated mountain goat behavioral activity budgets across alpine temperature gradients in Southeast Alaska using focal animal sampling and scan sampling techniques. I tested the effects of temperature on mountain goat activity and mountain goat elevation. Coupled with the behavioral investigations, I simultaneously monitored elevational temperature gradients using an array of passive thermistors. By monitoring hourly temperatures and deriving near-surface lapse rates, I demonstrate the utility of downscaled, region-specific temperature-elevation profiles for ecological applications rather than making inferences based on broad spatial models. Except in winter, lapse rates within the study area were between -0.3°C 100m⁻¹ and -0.4°C 100m⁻¹, and were not inclusive of the global mean environmental lapse rate (-0.65°C 100m⁻¹). Mountain goats within the study area demonstrated behavioral conservation of their activity budgets by altering their orientation through space and time, rather than incurring thermal and/or nutritional deficits. In addition, the animals took advantage of cooler temperatures at high elevations to bolster thermoneutrality. I highlight the need for behavioral ecology research that links physiological mechanisms and mammalian life history in an effort to predict the fate of a sentinel wildlife species as it copes with a changing environment. Indeed, such indicator species are invaluable to understanding the dynamics of change in ecosystem structure, function, and phenology. Given current warming trends and projections of changing climate regimes being more pronounced at higher latitudes, there is a marked need to better understand thermoregulatory constraints on faunal behavior and the effect of changing landscapes on the distributions and survival of wildlife populations in Alaska.