Direct and indirect costs of parasitism preceding a population decline of an Arctic ungulate

In the Arctic, muskoxen occur in a highly seasonal environment and must rely on finite energetic resources for survival and productivity. In this work, we have figured out that high adult nematode abundance was associated with lower body condition and high parasite abundance was associated with female reproduction, including the indirect effect on body condition. Our findings suggest that individuals prioritize energetic reserves for reproduction over parasite defence. In fall 2003, a severe icing event that restricted access to forage was associated with high overwinter mortality of muskoxen and a population crash. Through direct and indirect costs of parasite infection on body condition and reproduction, the high abundance of parasites may have contributed to the effects of this extreme weather event.

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