Tooth microwear texture in odontocete whales: variation with tooth characteristics and implications for dietary analysis

Understanding the diets and trophic relationships of toothed whales is central to understanding their roles in marine ecosystems, and associated conservation issues. Yet this is problematic because direct observation of what free ranging marine mammals eat is difficult. Quantitative 3D textural analysis of tooth microwear (DMTA) offers a new way of investigating diet in odontocetes and other marine mammals, but the application of this approach requires that we first understand how non-dietary variables affect the texture of microwear in odontocetes. Here we present the first analysis of microwear texture in odontocetes (beluga, Delphinapterus leucas) testing null hypotheses that microwear texture does not vary with dental surface tissue type (dentine, cementum), and that microwear texture does not vary with tooth characteristics (location in jaw, degree of wear, wear facet slope and facet orientation). Our results reveal that these variables have a significant impact on microwear textures, and thus have the potential to mask variation in texture caused by dietary differences. This does not mean that microwear texture analysis cannot be used as a tool for dietary analysis in toothed whales, but any future studies should adopt sampling protocols that standardize non-dietary variables to mitigate their effects in DMTA analysis.