The chemical composition of narwhal tusk and tooth is impacted by geographical locality.

Abstract

The possible relationship between diet and geographical locality is important for understanding the putative effects of climate change on animal behaviour and survival. Narwhals have two maxillary teeth, one of which may become a tusk. In these teeth, various chemical elements are incorporated and stored at the time of tooth formation. Here, we use inductively coupled plasma optical emission spectroscopy to investigate 12 chemical elements in tooth powder drilled from a total of 197 narwhal teeth from both sexes, tusks, embedded teeth, dentin, cementum and different geographical localities around Greenland. Additionally, the spatial distribution of Sr and Zn was mapped on a slice of tusk using X-ray fluorescence. Quantifications of Ca and P showed a mean degree of mineralization of 0.565 g g-1 and their relationship enabled the determination of the presence of approximately 1 wt% non-biomineral-associated P, which must be associated with biomolecules. While several differences were found across sampling parameters, no significant differences were found between males and females for any elements. Finally, the concentration of Cl, Ba, K and S depended on geographical locality; geographical locality was the only significant factor for Cl. These differences could potentially be linked to the circulation of freshwater from melting ice at and around Greenland.