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About the Churchill Fox Project

The Churchill Fox Project is a long-term research project established in 2010 by Dr. Jim Roth from the University of Manitoba. The project is primarily concerned with studying food web interactions at the transition between boreal forest and Arctic tundra, with a secondary focus on gaining a comprehensive understanding of the functional role played by Arctic foxes and red foxes at this ecotone.

Map of the Churchill Fox Project's study area near Churchill, MB, Canada along the western Hudson Bay coastline. The blue dots represent the 120 Arctic and red fox dens that we monitor each year, while the green triangles are the Churchill Northern Studies Centre (CNSC) and the four satellite field camps in Wapusk National Park (Nester 1 & 2, Broad River, and Owl River camps). Note the general habitat shift from west to east, of boreal forest (green landscape) to tundra (tan and yellow landscape).

The project is focused on the long-term monitoring and research of Arctic foxes, red foxes (the main competitor of Arctic foxes), and the numerous prey species that both fox species rely upon for food (including rodents such as collared lemmings and meadow voles; migratory birds; and seals) within the Greater Wapusk Ecosystem along the western Hudson Bay coastline in northern Manitoba. Although much of our research centers around monitoring these food web dynamics on the tundra, the Greater Wapusk Ecosystem actually sits at the intersection of three major biomes: the boreal forest, the Arctic tundra, and the marine environment. Boundaries between these biomes are easily crossed by mobile species, like foxes (particularly in winter when sea ice is present), which results in a series of complex, multi-biome interactions that make the Greater Wapusk Ecosystem food web unique.

Arctic foxes are considered generalist predators, which means that they have flexible diets and will eat just about any accessible foods. But in the Greater Wapusk Ecosystem (and elsewhere in the Arctic fox range) they prefer to hunt and eat small rodents — namely lemmings and voles — when they are abundant and readily available. Rodent populations in the Arctic are notorious for their population booms and busts at 3- to 5-year intervals, which are commonly referred to as 'population cycles'. Arctic fox populations generally track these rodent population cycles closely: when rodent populations are booming, the fox population climbs; but when the rodent populations crash, the fox populations also decline in tandem. However, the collared lemming population size in our study area has dramatically declined over the past several decades, meaning that the difference in population size between boom and bust phases has likewise decreased.


Arctic fox in its summer coat sitting on a den on the tundra in Wapusk.

C. Warrett Rodrigues

A collared lemming sitting just outside of its burrow on the tundra.

C. Warrett Rodrigues

Besides rodents, the other main prey items for Arctic foxes in our study area are migratory waterfowl and seals. The Greater Wapusk Ecosystem supports abundant breeding populations of migratory waterfowl during summer, including Canada geese, lesser snow geese, and common eiders. Arctic foxes will steal eggs from these birds during the nesting season and kill the vulnerable chicks once the eggs have hatched. The foxes have also adapted their behavior to exploit the summer influx of birds: they often cache eggs and carcasses throughout the tundra, which provides a stable food source for the foxes once the birds head south for the winter. During winter, Arctic foxes in our area can also take advantage of the frozen Hudson Bay and venture out onto the sea ice to kill ringed seal pups and scavenge the carcasses of adult seals killed by polar bears. When rodent populations are in a bust phase, foxes will adjust their hunting behavior and focus more time and energy on these secondary prey species to compensate for the lower rodent abundance on land.


Arctic fox running on the sea ice. A. Eby

Arctic foxes will re-use the same den sites on the tundra for decades, maybe even hundreds of years. This is mainly because the ground is still frozen when Arctic foxes give birth (usually between April and June), which greatly hinders their ability to dig out new dens. It is much easier to use dens that have already been dug out by foxes in previous years! As a consequence of the frequent re-use of dens, through time there is a steady accumulation of nutrients deposited at den sites from the foxes themselves — in the form of excrement (urine and feces) and prey remains. Adult foxes bring back food items from across the tundra to feed their pups, and the rotting carcasses and indigestible material (feathers, hair, bones) break down over time and enrich the soil around the dens. Additionally, Arctic foxes have the largest average litter sizes of any canid species, which means there are lots of animals present that are defecating and urinating on the dens and thus providing another important source of natural fertilizer.


A rotting goose carcass on an Arctic fox den. S. Johnson-Bice

The combination of high nutrient concentrations and repeated soil disturbance via their digging activities — some dens have as many as 100 burrow entrances! — results in an ecological hotspot on the tundra. Lush, enriched vegetation grows on and around fox dens, creating bright green landmarks on the landscape (see aerial photo below). Their characteristic appearance has even earned Arctic fox dens the nickname of 'the gardens of the tundra'. Because of their unique ability to modify their environment at den sites, Arctic foxes are considered to be ecosystem engineers. Another major aspect of the Churchill Fox Project is focused on understanding the myriad ways Arctic fox ecosystem engineering functions, and what effects their engineering activity has on other organisms (both plants and animals) and the ecosystem as a whole.


Aerial view of an Arctic fox den. Note the lush, tall vegetation that stands out against the rest of the tundra landscape. S. Johnson-Bice

Under the umbrella of our long-term monitoring program, we are also interested in understanding how climate change affects the Greater Wapusk Ecosystem food web. The Arctic has been disproportionately affected by human-caused climate change, and these effects can profoundly influence coastal tundra ecosystems. Indeed, climate change is a major reason why lemming abundance has declined over the past several decades: warmer winter temperatures negatively affect the quality and amount of snowpack on the tundra, and lemmings rely on deep, high-quality snowpack for their winter habitat.

Climate change has also negatively influenced the duration that Hudson Bay is covered by sea ice — the number of days Hudson Bay is covered by sea ice has declined by an average of 5.5 days per decade since 1979 — which has indirectly had adverse effects for Arctic foxes. With shorter sea ice seasons, animals like Arctic foxes that rely on sea ice for winter food resources are forced to stay on land longer in the fall and come ashore sooner in the spring than in the past, which effectively limits the length of time that Arctic foxes can consume seals. This reduced availability of seals, in combination with the lower overall rodent abundance, has resulted in a long-term decline in the Greater Wapusk Arctic fox population size.


Sea ice melting in Hudson Bay during spring. C. Warret Rodrigues

As climate change progresses and the Arctic continues to warm, species that are native to the boreal forest biome are expected to expand northward onto the tundra. In fact, the expansion of boreal forest animals onto the tundra has already begun in the Greater Wapusk Ecosystem — specifically, the expansion of red foxes and meadow voles. Recent research from our project has shown that meadow voles, a native boreal species, are now a major component of Arctic fox diets when they were absent a little more than a decade ago.


Red fox carrying prey in its mouth. C. Warrett Rodrigues

A red-backed vole captured as part of our long-term rodent monitoring in the boreal forest section of the study area. M. Dudenhoeffer

Once scarce on the Wapusk tundra, we have also observed an increased presence of red foxes on the tundra in recent years. Because red foxes are bigger than Arctic foxes they are the dominant competitors when the two species interact, and can therefore exclude them from food resources and den sites. Red foxes now breed and occupy dens throughout the Greater Wapusk Ecosystem, which may ultimately negatively affect resident Arctic foxes. Assessing how and to what extent red foxes compete with Arctic foxes in the Greater Wapusk Ecosystem is another major focus of our project.

By monitoring the numerous species that inhabit the Greater Wapusk Ecosystem, we hope to gain a better understanding of the complex food web interactions within this unique ecosystem and anticipate how these interactions may alter as global climate change progresses. The perseverance and continuity of long-term research projects like ours is critically important for advancing the research, conservation, and management of the natural world. We hope our project provides valuable contributions towards these objectives.


Churchill Fox Project leader Jim Roth instructs students from his Arctic Field Ecology course on how to set up a rodent trapping grid. S-T Zhao.

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