GSA Connects 2023 Meeting in Pittsburgh, Pennsylvania

Paper No. 57-13
Presentation Time: 4:50 PM

VARIATION IN STABLE CARBON (Δ13C) AND NITROGEN (Δ15N) ISOTOPE COMPOSITIONS ALONG ANTLERS OF QAMANIRJUAQ CARIBOU (RANGIFER TARANDUS GROENLANDICUS)


BRENNING, Matthew, Earth Science, Carleton University, 1125 COLONEL BY DRIVE, Ottawa, ON K1S 5B6, Canada, LONGSTAFFE, Fred J., Department of Earth Sciences, University of Western Ontario, London, ON N6A 5B7, Canada and FRASER, Danielle, Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, 10th St and Constitution Ave, N.W., Washington, DC 20013-7012

Male and female Caribou (Rangifer tarandus groenlandicus) from the Qamanirjuaq herd (Nunavut, Canada) grow antlers throughout the summer season, beginning at the start of the spring migration for both male and female and ending before the fall rut for male and after for female. Throughout antler growth, stable isotopes of carbon (δ13C) and nitrogen (δ15N) are incorporated into the tissue. As such, yearly antler shedding provides a non-lethal source of data for studying short and long-term changes in caribou ecology. We sampled the antlers of thirteen males and fifteen females culled from the Qamanirjuaq herd in September 1967. We predicted that serial sampling of antlers would reflect the known seasonal dietary change from lichen to a shrub and grass-like plant diet, as found in rumen contents from individuals culled during the same period. Values of δ13C and δ15N were analyzed for food sources as well as for collagen sampled sequentially along each antler’s length. The stable carbon isotope compositions of collagen (δ13Ccol) varied among individuals and within antlers by ~0.5‰ for males and by ~1‰ for females. Values of δ15Ncol increased within all antlers by 1~3‰ from pedicle to tip and varied by 3‰ among all individuals sampled. Bayesian mixing models produced using these data indicated mixed diets of fungi, horsetail, lichen, and woody plants but did not reveal significant dietary shifts for any individual during antler formation. The measured increases in δ15Ncol of antler tissue may correspond to subtle seasonal dietary changes and/or variations in nutritional stress.