The implications for paleodietary and paleoclimatic reconstructions of intrapopulation variability in the oxygen and carbon isotopes of teeth from modern feral horses

摘要

We analyzed the isotopic patterns found in the tooth enamel of modem feral horses from Shackleford Banks, North Carolina (USA), which has a temperate climate and supports primarily C-4 grasslands. Enamel delta(13)C values averaged -4. 1 parts per thousand with a standard deviation (1 sigma) of 1.7 parts per thousand, which corresponds to an average diet of 66 +/- 12% C-4 plants. Our results differ from dietary reconstructions from 1978 to 1981, which found that horses consumed 91% C-4 plants. This suggests that horses have increased their consumption Of C-3 forbs, likely as a result of the removal of cattle, sheep, and goats from the island. Shackleford surface waters had delta(18) Omicron values that averaged -3.3 +/- 0.5 parts per thousand and - 1.3 +/- 1.8 parts per thousand on the western and eastern ends of the island, respectively. Tooth enamel samples averaged 27.3 +/- 1.5 parts per thousand and displayed the same range of delta(18)Omicron values as surface waters. The variability of both delta(18) Omicron and the delta(13)C values among individuals within this population demonstrates that horses from relatively homogenous temperate environments can display a wide range of isotopic values. Given the observed range of isotopic values for modem horses, we suggest that researchers use the mean values of multiple (>= 9) equids when attempting to reconstruct average paleodiets and/or paleoenvironmental conditions. (c) 2005 University of Washington. All rights reserved.