Toxic and essential trace element concentrations in Pacific walrus ( Odobenus rosmarus divergens ) skeletal muscle varies by location and reproductive status

Changes to Pacific walruses ( Odobenus rosmarus divergens ) habitat and foraging behavior may affect exposure to both toxic and essential trace elements in walrus tissue. This study measured the trace element concentrations of silver (Ag), arsenic (As), cadmium (Cd), cobalt (Co), copper (Cu), nickel (Ni), total (THg) and methyl mercury (MeHg), selenium (Se), lead (Pb), and zinc (Zn) in walrus skeletal muscle sampled during 2009–2015. Females had significantly higher concentrations of THg ( p = 0.021), MeHg ( p = 0.037), Cd ( p = 0.021), Cu ( p = 0.003), and Se ( p = 0.001) compared to males. Females with no calf had significantly higher concentrations of Cd compared to females with a calf ( p = 0.001) and pregnant females and females with a calf had significantly lower Se concentrations compared to females with a yearling or no calf ( p < 0.05). Bering Sea males had significantly higher Ni concentrations ( p = 0.001) and significantly lower Se ( p = 0.006) and Zn concentrations ( p = 0.001) compared to other locations. THg, MeHg, and As tissue concentrations decreased with age ( p < 0.01), suggesting these toxic elements are not accumulating in this tissue while Cd increased with age ( p < 0.05). The narrower range in element concentrations among pregnant and nursing females may indicate less variation in prey species, and coupled with the reproductive needs for essential elements, suggests they may be more vulnerable to changes in prey availability compared to other walruses.