WALRUS LIFE-HISTORY MOVEMENTS RECONSTRUCTED FROM LEAD ISOTOPES IN ANNUAL LAYERS OF TEETH

Putative life history movements of male Atlantic walrus (Odobenus rosmarus nsmarus) harvested at Sanirajak in northern Foxe Basin, Canada, were reconstructed by comparing Pb isotopes in tooth cementum growth layer groups (GLGs) to those in whole‐cementum samples from other walrus of Foxe Basin and nearby areas. The analyses yielded three life history patterns including one, “prodigal sons,” not previously recognized in large mammals. Isotope ratios in GLGs of “local” Sanirajak walrus were relatively constant over time and similar to the whole‐cementum data for most walrus caught in northern Foxe Basin. An “immigrant” walrus acquired the local signal only in young adulthood. In two “prodigal sons,” GLG Pb isotope ratios changed significantly from the local signature after weaning but returned to it in late maturity, shortly before being harvested. Possible recruitment and dispersal areas for the two types of outliers included regions in northern and eastern Hudson Bay, some 300–600 km distant. The return of mature males to their natal group after associating with other groups for several years, as seen in some of the walrus, may be more common among mammals than previously thought. However, without a reconsttuctive technique such as employed here, it could only be detected through long‐term studies of known individuals and all the relevant social groups.