Assessment of anadromous salmon resources in the diet of the Alexander Archipelago wolf using stable isotope analysis

The Alexander Archipelago wolf (Canis lupus ligoni) is unique to southeast Alaska, occurring on islands south of Frederick Sound and along the mainlan d between Dixon Entrance and Yakutat Bay. Sitka blacktailed deer (Odocoileu s hemionus sitkensis) are an important prey species for wolves across the s outhern part of the region. Spawning salmon (Onchorynchus sp.) are seasonal ly available but their presence in wolf diets has not previously been quant ified. We examined the range of bone collagen delta(13)C and delta(15)N val ues for wolves throughout southeast (n = 163) and interior (n = 50) Alaska and used a dual-isotope mixing model to determine the relative contribution of salmon-derived marine protein in the diet. Southeast Alaska wolves cons umed significantly more salmon (mean +/- SE: 18.3 +/- 1.2%) than did wolves from interior Alaska (9.1 +/- 0.6%, P<0.001). Wolves on the southeast Alas ka mainland appeared to have higher marine isotopic signatures than island wolves, although this difference was not significant. Variation among indiv idual wolf diets was higher for southeast than for interior Alaska wolves, and variation was highest in coastal mainland wolf diets (P < 0.001). Marin e resources may augment the diet of southeast Alaska wolves during seasonal or annual fluctuations in the availability of deer, particularly in those areas on the mainland where densities of terrestrial ungulates are relative ly low.