Elemental bioaccumulation as trophic discriminator in Southeast Alaska gray wolves: Marine-terrestrial diet shifts

Abstract

Gray wolves (Canis lupus) in Southeast Alaska exhibit diverse foraging strategies shaped by regional ecological factors. Stable isotope (δ¹³C and δ¹⁵N) and trace element (TE) analyses were used to evaluate dietary patterns and contaminant exposure in four wolf populations from northern Lynn Canal (Douglas Island, Juneau, Gustavus, and Pleasant Island) from wolf hair samples collected from 2013–2021, along with sea otter (Enhydra lutris) hair in wolf scat collected in 2018–2019. Stable isotope ratios revealed that Juneau wolves predominantly consume terrestrial prey such as Sitka black-tailed deer (Odocoileus hemionus sitkensis) and mountain goats (Oreamnos americanus), and wolves on Douglas Island mainly consume Sitka black-tailed deer. In contrast, wolves from Gustavus and Pleasant Island exhibited enriched isotopic signatures, indicating a significant incorporation of marine-derived prey, particularly sea otters. Analysis of TEs revealed higher concentrations in wolves consuming marine-based diets, highlighting potential bioaccumulation risks compared to terrestrial-based diets. Gustavus wolves had the highest geometric mean concentrations for Cr (1.63 µg/g), Hg (4.24 µg/g), and Mo (0.180 µg/g) while Pleasant Island wolves had the highest for Al (153 µg/g), Cd (0.160 µg/g), Co (0.208 µg/g), Fe (343 µg/g), Mn (52.1 µg/g), and V (0.592 µg/g). The Se:Hg ratio also indicated a higher likelihood of mercury toxicity in all wolf populations, underscoring environmental health concerns. Assessing the dietary preferences and prey availability of apex predators, alongside the potential risks posed by elevated TE concentrations, is essential for informing targeted conservation strategies aimed at safeguarding these species across both coastal and inland Southeast Alaska.