HR: 0800h
AN: B21B-0885    [Abstracts]
TI: Deciphering Seasonal Variations of Diet and Water in Modern White-Tailed Deer by {\it In Situ} Analysis of Osteons in Cortical Bone
AU: * Larson, T E
EM: tlarson@uwo.ca
AF: The Universtiy of Western Ontario, Dept. of Earth Sciences Bio-Geo Bldg. Rm 128A, London, ON N6A5B7 Canada
AU: Longstaffe, F J
EM: flongsta@uwo.ca
AF: The Universtiy of Western Ontario, Dept. of Earth Sciences Bio-Geo Bldg. Rm 128A, London, ON N6A5B7 Canada
AB: {\it In situ} stable carbon and oxygen isotope compositions of biogenic apatite were obtained from longitudinally-cut sections of cortical bone from femurs of modern domesticated sheep and free-range White-Tailed deer, using an IR-laser and a GC-continuous flow interface. Ablation pits averaged 200x50 microns, making it possible to analyze individual osteons. Since cortical bone is remodelled along osteons throughout a mammal's lifetime, isotopic data at this resolution provides information about seasonal variations in diet and drinking water. The O-isotope results were calibrated using laser analyses of NBS-18 and NBS-19, which produced a value of 26.39$\pm$0.46 permil (n=27) for WS-1 calcite (accepted value, 26.25 permil). C-isotope results were calibrated using a CO$_{2}$ reference gas, producing a value of 0.76$\pm$0.40permil (n=27) for WS-1, also in excellent agreement with its accepted value of 0.74 permil. Average O- and C-isotope values for a local domestic sheep (southwestern Ontario, Canada) were 12.20$\pm$0.58 and -15.70$\pm$0.35 permil (n=27), respectively. No isotopic trend occurred along or across individual osteons. This pattern is consistent with the sheep's relatively unchanging food and water sources. The free-range White-Tailed deer came from Pinery Provincial Park (PPP), southwestern Ontario. Its O- and C-isotope compositions varied systematically across individual osteons and were negatively correlated (R$^{2}$=0.56). O-isotope values ranged from 13.4 to 15.5 permil; the highest values correlated with summer and the lowest values, with winter. The O-isotope compositions of the main water source (Old Ausable River Channel) varied similarly during the deer's lifetime: winter average, -10.7$\pm$0.5 permil; summer average, -8.6$\pm$0.4 permil. The C-isotope results for the deer osteons varied from -19.7 to -15.9 permil. This variation can be explained by changes in food sources. Summer diets of deer in PPP consist mainly of leafy fractions of C3 vegetation, especially sumac, cedar, oak and pine (average leaf C-isotope value, -28.4$\pm$0.8 permil). During winter, when leafy material is unavailable and deep snow inhibits access to vegetation in general, deer strip bark from vegetation (average bark C-isotope value, -25.6$\pm$0.8 permil). Certain C4 grasses (little bluestem and sandreed grass, average C-isotope value, -12.7$\pm$0.2 permil), which are abundant in unforested dune areas of PPP, commonly stand above the snow cover, and hence are also available for consumption. Deer may also range more widely in the winter, feeding on corn stalks and husks that escaped both harvest and snow cover (average C-isotope value, -11.3$\pm$0.2 permil).
DE: 1694 Instruments and techniques
DE: 1040 Isotopic composition/chemistry
DE: 1045 Low-temperature geochemistry
DE: 1615 Biogeochemical processes (4805)
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting