Cryosphere changes drive an Arctic fox decline at the Arctic’s edge

Abstract

Abstract Responses of one species to changing climate may influence population dynamics of others, particularly in the Arctic where food webs are strongly linked. Specifically, changes to the cryosphere can limit prey availability for predators. We examined Arctic fox (Vulpes lagopus) and red fox (V. vulpes) population trends near the southern edge of the Arctic fox distribution using fox harvest data from Churchill, Manitoba from 1955–2014. Arctic fox harvest, corrected for trapping effort, declined over time, whereas the red fox harvest was stable. The positive relationship between the number of harvested Arctic foxes and red foxes suggested interspecific competition did not promote the Arctic fox decline. To investigate alternative mechanisms, we compared harvest estimates to climate, sea-ice phenology, and snowpack characteristics in a series of models using Akaike’s Information Criterion. We examined two time periods: the full 60 years (1955–2014) and the most recent 25 years when climate change has been most intense (1989–2014). The strongest influences on Arctic fox harvest were snow thickness in February (1955–2014) and the length of the summer ice-free period (1989–2014). Thicker snow may benefit lemmings, their primary year-round prey, by creating an insulated microclimate that promotes winter population growth. Earlier sea-ice breakup and later freeze-up on Hudson Bay may reduce access to seal carrion as an alternative winter food source when lemming densities decline. Predators have an important ecological role, so understanding the influence of changes in cryosphere on predator-prey interactions may better illuminate the broader influence of climate change on food-web dynamics.