Temporal variability in arctic fox diet as reflected in stable-carbon isotopes; the importance of sea ice

Abstract

Consumption of marine foods by terrestrial predators can lead to increased predator densities, potentially impacting their terrestrial resources. For arctic foxes (Alopex lagopus), access to such marine foods in winter depends on sea ice, which is threatened by global climate change. To quantify the importance of marine foods (seal carrion and seal pups) and document temporal variation in arctic fox diet I measured the ratios of the stable isotopes of carbon ((13)C/(12)C) in hair of arctic foxes near Cape Churchill, Manitoba, from 1994 to 1997. These hair samples were compared to the stable carbon isotope ratios of several prey species. Isotopic differences between seasonally dimorphic pelage types indicated a diet with a greater marine content in winter when sea ice provided access to seal carrion. Annual variation in arctic fox diet in both summer and winter was correlated with lemming abundance. Marine food sources became much more important in winters with low lemming populations, accounting for nearly half of the winter protein intake following a lemming decline. Potential alternative summer foods with isotopic signatures differing from lemmings included goose eggs and caribou, but these were unavailable in winter. Reliance on marine food sources in winter during periods of low lemming density demonstrates the importance of the sea ice as a potential habitat for this arctic fox population and suggests that a continued decline in sea ice extent will disrupt an important link between the marine and terrestrial ecosystems.

Effect of resource subsidies on predator–prey population dynamics: a mathematical model

“…The use of secondary resources by species from adjacent habitats or ecosystems is widespread [46,50,52]. These allochthonous resources, or resource subsidies, can strongly affect the abundance and space use of consumers in recipient ecosystems, with cascading effects on in situ resources [28,30,38,50,53].…”

“…Our motivating example shall be that of the predation of arctic foxes (Alopex lagopus) on lemmings (Cricetidae family). In coastal habitats, arctic foxes are believed to partially subsist in the winter on both the local lemming population and a resource subsidy, namely seal (Phocidae family) carcasses, which are provided by polar bear (Ursus maritimus) predation on the sea ice [52]. Our primary interest is to determine situations in which dynamical stability and instability occur so as to understand more fully how resource subsidies may impact predators and their prey.…”

Foraging Behaviours and Population Dynamics of Arctic Foxes

“…Foxes were marked with plastic ear-tags which were used to distinguish local foxes from potential immigrants (see below). The metabolic turn-over rate of blood is about 1 month whereas fur is metabolically inactive (Hobson 1999); stable isotope signatures in blood therefore represented spring diets whereas those from winter-fur represented diets from the previous fall when the fur was grown (Roth 2002).…”

Effects of subsidies from spawning chum and pink salmon on juvenile coho salmon body size and migration timing

“…Geophysical processes and organisms can transport nutrients across ecological boundaries, thus linking an array of environments, such as above-and below-ground terrestrial systems (Scheu 2001), sea ice and arctic islands (Roth 2002), and streams and forests (Nakano and Murakami 2001). Productive systems can subsidize nutrient-limited ones (Gravel et al 2010), such as when nutrients move from the marine environment to desert islands (Spiller et al 2010) and freshwater streams (Richardson et al 2010).…”