COS 239-3 - Fecal DNA metabarcoding reveals extensive marine resource utilization by coastal wolves in Southwest Alaska

Abstract: Gray wolves (Canis lupus) throughout most of their range are assumed to be obligate ungulate predators, but wolf populations with access to resource subsidies from the marine system may demonstrate incredible dietary flexibility. Wolves are seen frequently on the 500-mile coastline of Katmai National Park & Preserve in Southwest Alaska, but their role as generalist carnivores in the nearshore system is not well understood. On the Katmai coast, moose (Alces alces) occur at low density while sea otters (Enhydra lutris), Pacific salmon (Oncorhynchus spp.), and other marine species are abundant. We hypothesized that these unique circumstances of prey availability drive coastal wolves to hunt and forage extensively in the marine system, exploiting seasonal salmon availability, vulnerable marine mammals, and intertidal forage items. Katmai coastal wolves have been observed catching salmon alongside bears, carrying sea otter carcasses up the beach, and actively hunting adult harbor seals (Phoca vitulina) and sea otters at haul-outs. In 2019 we began using noninvasive genetic sampling techniques and automatic digital cameras to study wolf foraging ecology on the Katmai coast. The main objectives of this study were to reconstruct coastal wolf diet via fecal DNA metabarcoding and capture wolves foraging and hunting in the marine system on trail cameras. In the summer of 2021 from June through September, we deployed trail cameras and collected approximately 800 wolf scat samples from seven distinct sites along Katmai’s coastline. DNA metabarcoding results from 545 of these samples identified 67 unique vertebrate prey species, including a diversity of marine prey items. Sea otters were the most common prey species overall, with their DNA detected in 166 wolf scats ( >30%). Salmon were detected in 151 scats (28%), while other oceanic fish species occurred in 72 scats (13%). Sea otters were consumed by wolves at all seven study sites. Marine species constituted more than 50% of prey item occurrences for six out of seven study sites. Trail cameras at several sites captured wolf fishing behavior and wolves frequenting marine mammal haul-out sites. Our findings demonstrate the importance of cross-boundary resource subsidies for large carnivores in coastal Alaska and demonstrate the incredible dietary flexibility of wolves. Our results indicate that sea otter recolonization of the Gulf of Alaska has likely restored a historically present food web linkage between a terrestrial and marine apex predator with potential cascading effects for the nearshore ecosystem.