Determining the relationships between forage use, climate and nutritional status of barren ground caribou, Rangifer tarandus groenlandicus, on Southampton Island, Nunavut, using stable isotopes analysis of d 13C and d 15N

Abstract

The caribou (Rangifer tarandus groenlandicus) on Southampton Island, Nunavut, Canada for the years 1998-2000 and 2004, 2005, were investigated using stable isotope analysis (SIA) of carbon (d 13C) and nitrogen (d 15N). Spring signatures of rumen contents and muscle samples were correlated with standard biological measures of back fat and Riney kidney fat index. Caribou d 13C and d 15N ratios, together with detailed rumen content analysis, show that SIA data yields a time-integrated signal reflective of spatial and temporal variation in feeding ecology and as such is capable of detecting trophic interactions. Rumen content signatures provide current indication of forage selection, while muscle tissue signatures reflect bulk summer seasonal diet and in combination with rumen signatures, can help identify potential shifts in winter diet and the potential for short-term changes in caribou condition. <br /><br /> d 13C and d 15N signatures for major forage species categories were also compared to variations in rumen content and muscle signatures to investigate possible changes in forage preference. The results indicate that SIA is capable of assessing the importance of seasonal habitat use with regard to seasonal food intake. Stable isotopes analysis (SIA) was also used to investigate the effects of winter snow thickness and temperature on caribou (Rangifer tarandus), on Southampton Island. Variations found in isotope signatures of rumen content and muscle indicated that differences in winter climate conditions may affect forage selection, and impact on animal condition.