The foraging behavior of arctic foxes was observed in a waterfowl nesting area on the Yukon–Kuskokwim Delta of Alaska in 1985–1986. Observations were made during peak fox activity from two towers, 3 m high, located in different community types. Data were collected continuously for individual foxes on specific activities, the community in which activities occurred, and the type of food obtained. After migratory birds started nesting in the area, the food potentially available to foxes changed from microtines, old caches, and carrion to include eggs and birds. This change was reflected in the foraging behavior of the foxes as they switched to predation on eggs. After nesting began, the search success rate of foxes increased (from <30% to >50%) and search duration decreased (mean 19.7 s before nest initiation versus mean 9.4 s in mid-incubation) as the rate of food acquisition increased. Over 80% of the eggs taken by foxes were cached rather than eaten immediately, which extended the availability of this temporally limited resource to foxes. Eggs were the primary prey of arctic foxes during the nesting stages in both years, even though microtine populations were high in one year (1985) and low in the other (1986).

Climate change can have a marked effect on the distribution and abundance of some species, as well as their interspecific interactions. In 1992, before ecological effects of anthropogenic climate change had developed into a topical research field, Hersteinsson and Macdonald published a seminal paper hypothesizing that the northern distribution limit of the red fox (Vulpes vulpes) is determined by food availability and ultimately climate, while the southern distribution limit of the Arctic fox (Vulpes lagopus) is determined by interspecific competition with the larger red fox. This hypothesis has inspired extensive research in several parts of the circumpolar distribution range of the Arctic fox. Over the past 25 years, it was shown that red foxes can exclude Arctic foxes from dens, space and food resources, and that red foxes kill and sometimes consume Arctic foxes. When the red fox increases to ecologically effective densities, it can cause Arctic fox decline, extirpation and range contraction, while conservation actions involving red fox culling can lead to Arctic fox recovery. Red fox advance in productive tundra, concurrent with Arctic fox retreat from this habitat, support the original hypothesis that climate warming will alter the geographical ranges of the species. However, recent studies show that anthropogenic subsidies also drive red fox advance, allowing red fox establishment north of its climate-imposed distribution limit. We conclude that synergies between anthropogenic subsidies and climate warming will speed up Arctic ecosystem change, allowing mobile species to establish and thrive in human-provided refugia, with potential spill-over effects in surrounding ecosystems.

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Gosling body mass can affect first year survival, recruitment, adult body size, and future fecundity of geese, and can serve as an indicator of forage availability and quality on brood-rearing areas. From 2012-2014 we measured body mass of 76 black brant (Branta bernicla nigricans) and 268 lesser snow goose (Chen caerulescens caerulescens) goslings of known age on the Colville River Delta (CRD) of northern Alaska to determine if there was evidence of density-dependent declines in gosling growth following recent population increases of those species and sympatric greater white-fronted geese (Anser albifrons frontalis). We contrasted contemporary body mass of brant goslings and forage biomass in brood-rearing habitats that were shared by all species, with measures obtained on, and near the CRD in the 1990s, prior to the establishment of snow goose nesting colonies in the area. Body mass of brant goslings recaptured between 25 and 32 days of age had not changed over the past 2 decades, despite an influx of snow geese, and increases in populations of brant and white-fronted geese. At 30 days of age, body mass of brant goslings on the CRD was 100-400 g heavier than for brant goslings of the same age on the Yukon-Kuskokwim Delta (YKD), Alaska. Contemporary biomass of grazed Carex subspathacea on CRD brood-rearing areas was comparable to the 1990s and was 2-4 times greater than for the same plant community on the YKD. Historical data on growth of snow goose goslings were not available for the CRD. However, average body mass of 34-day-old snow goose goslings was >230 g heavier than for conspecifics of the same age in the Hudson Bay region. We conclude that the establishment of nesting snow geese on the CRD has not negatively affected brant gosling growth, and that recent population increases of all species have likely not been constrained by forage availability on brood-rearing areas. Barring demographic changes elsewhere in their annual cycles, we predict that goose populations will continue to increase in northern Alaska. However, snow geese are increasing more rapidly than brant in the region. Because the black brant population has periodically been below conservation objectives, the effects of the increasing number of snow geese on forage biomass and growth of brant goslings in northern Alaska should be monitored. Ó 2017 The Wildlife Society.

The biodiversity working group of the Arctic Council has developed pan-Arctic biodiversity monitoring plans to improve our ability to detect, understand and report on long-term change in Arctic biodiversity. The Arctic fox (Vulpes lagopus) was identified as a target of future monitoring because of its circumpolar distribution, ecological importance and reliance on Arctic ecosystems. We provide the first exhaustive survey of contemporary Arctic fox monitoring programmes, describing 34 projects located in eight countries. Monitored populations covered equally the four climate zones of the species' distribution, and there were large differences between populations in long-term trends, multi-annual fluctuations, diet composition, degree of competition with red fox and human interferences. Den density, number of active dens, number of breeding dens and litter size were assessed in almost all populations, while projects varied greatly with respect to monitoring of other variables indicative of population status, ecosystem state or ecosystem function. We review the benefits, opportunities and challenges to increased integration of monitoring projects. We argue that better harmonizing protocols of data collection and data management would allow new questions to be addressed while adding tremendous value to individual projects. However, despite many opportunities, challenges remain. We offer six recommendations that represent decisive progress toward a better integration of Arctic fox monitoring projects. Further, our work serves as a template that can be used to integrate monitoring efforts of other species, thereby providing a key step for future assessments of global biodiversity.