STABLE ISOTOPE SIGNATURES OF MOOSE IN RELATION TO SEASONAL FORAGE COMPOSITION: A HYPOTHESIS

Abstract

Forage plants consumed by moose (Alces alces) during winter are isotopically divergent from the forage plants potentially eaten during summer. I examined the natural abundance of ¹⁵N and ¹³C in moose form north-central Alaska, USA, to test the hypothesis that seasonal variation (summer versus winter) in the isotopic composition of the diet can be used to make inferences about food habits across seasons through a temporal record in hooves of moose. Moose hooved collected from hunter-killed males during autumn exhibited temporal oscillations in stable isotope signatures for both carbon and nitrogen. Data on hoof growth in cervids and additional isotope data from immature moose strongly suggest that observed variation in mature animals reflected diet, and comprised a time frame of slightly < 2 years. This isotopic technique has the potential for reconstruction of diets in moose throughout the year without repeated sampling over that time interval, and allows for comparisons of diets among regional populations without extensive fieldwork.