The Gray Wolves, Canis Lupus, of British Columbia’s Central and North Coast: Distribution and Conservation Assessment

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Seasonal shifts in diet are widespread, but our ability to detect them can be limited. Comparisons of stable isotope signatures in metabolically inert tissue portions grown at different times are inadequately exploited in dietary reconstructions. We propose that segments of guard hair can index diet to periods of growth (i.e., seasons differing in resource availability). We examined inter-hair δ13C and δ15N signatures from gray wolves (Canis lupus) of British Columbia to test whether the bulk of enriched (marine-derived) nutrients was assimilated during fall, the peak of salmon (Onchorynchus spp.) migration. In five animals, we detected a seasonal dietary shift: relatively more 13C and 15N was assimilated during fall than during summer, suggesting use of salmon during fall. Twelve wolves and both controls showed no seasonal shift in diet. Using salmon when available may be adaptive, given its predictability, spatial constraint, caloric content, and lower potential to inflict injury relative to that imposed by large mammals. Our study complements others that also used novel and fine-scale isotope approaches and may permit the identification of otherwise undetectable niche differentiation among conspecifics or heterospecifics.