The 84th Annual Meeting of the American Association of Physical Anthropologists (2015)

Sex-linked stable isotope isotope patterns in a Kenyan population of olive baboons (Papio anubis)


1Department of Anthropology, University of Minnesota, 2Department of Earth Sciences, University of Minnesota

March 28, 2015 , Gateway Ballroom 2/3/4/5 Add to calendar

Evolutionary anthropologists use stable isotope signatures to infer many aspects of the behavioral ecology of species. For example, carbon and oxygen isotopes have been used as evidence of weaning and dispersal patterns. Here we examine individuals of Papio anubis from the Neil Tappen Collection (University of Minnesota) to determine if males (n=16) and females (n= 18) record similar oxygen and carbon isotope signatures in their molars.

The difference between male (-0.36‰) and female (-0.21‰) mean oxygen isotope ratios was not significant (p=0.6). This suggests that the males in the population, who leave their natal troops at adulthood, did not disperse widely, as both male and female juveniles had access to water sources with the same isotopic composition.

Significant differences in oxygen isotope composition between the 1st, 2nd, and 3rd molars were found in females (M1:M2 p=0.02, M1:M3 p=0.05) but not males (M1:M2 p=0.5, M1:M3 p=0.9). In neither sex did the results reflect expected oxygen isotope patterns along the tooth row; oxygen isotopes should become less enriched in 18O from M1 to M3 due to weaning as breast milk is enriched in 18O compared to drinking water.

Enrichment of 13C from M1 to M3 in females was opposite that of males. Female M1s (-7.54‰, n=3) were enriched in 13C compared to M3s (-10.02‰, n=6), while male M1s (-9.86‰, n=7) were depleted in 13C compared to M3s (-7.06‰, n=4). This may reflect different weaning behaviors between the sexes, ontogenetic changes in diet composition, or changes in vegetation structure during each individual’s growth.