Oxygen isotope variations in phosphate of deer bones

Variations of δ18O of bone phosphate (δp) of white tailed deer were studied in samples with wide geographic distribution in North America. Bones from the same locality have similar isotopic values, and the difference between specimens (0.4‰) is not large relative to the measurement error (0.3‰). The total range of δp values is about 12‰. This indicates that deer use water from a relatively small area, and thus their δp indicates local environmental conditions. Multiple regression analysis between oxygen isotope composition of deer bone phosphate and of local relative humidity and precipitation (δw) yields a high correlation coefficient (0.95). This correlation is significantly better than the linear correlation (0.81) between δp and δw of precipitation alone. Thus δp depends on both isotopic composition of precipitation and on relative humidity. This is because deer obtain most of their water from leaves, the isotopic composition of which is partly controlled by relative humidity through evaporation/transpiration.