Mandibular growth layers as a means of determining the age at death of beluga whales (Delphinapterus leucas) in zooarchaeological assemblages

In order to determine mortality profiles in zooarchaeological assemblages, analysts typically observe patterns of tooth eruption and wear or patterns of incremental growth layers in tooth cementum or dentine. This paper presents a method for the determination of mortality profiles for beluga whales (Delphinapterus leucas), based on growth layers in mandibular bone, as opposed to teeth. This technique is refined through the experimental thin-sectioning of mandibles of eight beluga whales whose ages had previously been estimated on the basis of dental annuli, in order to determine the optimal location for the observation of readable mandibular growth layers. The technique is then applied to a sample of 68 beluga whale mandibles recovered from a late 19th century mass beluga kill site at Elwin Bay on Somerset Island in the central Canadian Arctic. The results are consistent with an expected catastrophic profile, and are also strongly supported through an independent comparison of mandible length with mandible age.