The origin, connectivity, and individual specialization of island wolves after deer extirpation

Wolves are assumed to be ungulate obligates, however, a recently described pack on Pleasant Island, Alaska USA, is persisting on sea otters and other marine resources without ungulate prey, violating this long-held assumption. We address questions about these wolves regarding their origin and fate, degree of isolation, risk of inbreeding depression, and diet specialization by individual and sex. We applied DNA metabarcoding and genotyping by amplicon sequencing using 957 scats collected from 2016 to 2022, and reduced representation sequencing of tissue samples to establish a detailed understanding of Pleasant Island wolf ecology and compare them with adjacent mainland wolves. Dietary overlap was higher among individual wolves on Pleasant Island (Pianka's index mean 0.95 +/- 0.03) compared to mainland wolves (0.70 +/- 0.21). The individual diets of island wolves were dominated by sea otter, ranging from 40.6% to 63.2% weighted percent of occurrence (wPOO) (mean 55.5 +/- 8.7). In contrast, individual mainland wolves primarily fed on ungulates (42.2 +/- 21.3) or voles during a population outbreak (31.2 +/- 23.2). We traced the origin of the Pleasant Island pack to a mainland pair that colonized around 2013 and produced several litters. After this breeding pair was killed, their female offspring and an immigrant male became the new breeders in 2019. We detected 20 individuals of which 8 (40%) were trapped and killed while two died of natural causes during the 6-year study. Except for the new breeding male, the pedigree analysis and genotype results showed no additional movement to or from the island, indicating limited dispersal but no evidence of inbreeding. Our findings suggest wolves exhibit more flexible foraging behavior than previously believed, and hunting strategies can substantially differ between individuals within or between packs. Nevertheless, anthropogenic and natural mortality combined with limited connectivity to the mainland may inhibit the continued persistence of Pleasant Island wolves. We applied DNA metabarcoding and SNP genotyping to quantify variation in marine foraging behavior within wolf packs, among sexes, and individuals using 957 scats collected from an island and the adjacent mainland from 2016 to 2022. Island wolves consistently consumed sea otters while mainland wolves fed mainly on ungulates and voles with more variation annually, among sexes and individuals, indicating both individual variation in the diet of a cooperatively hunting predator and varying hunting strategies among individuals within the same pack. We also found limited dispersal to and from the island with only one unrelated wolf coming from the mainland during the 6-year study period. Our findings suggest wolves are more flexible in their foraging strategies than is commonly appreciated and that the recolonization of sea otters can allow wolves to persist on predominantly non-ungulate, marine resources. Nevertheless, anthropogenic and natural mortality, and a lack of movement to and from the island may inhibit the continued persistence of the Pleasant Island wolves.image