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animal species

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  Arctic Fox  
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Arctic Fox
Arctic Foxes are the main predators found on Bylot Island and their favourite preys are small rodents called lemmings. Lemming populations are however cyclic, meaning that they go through phases of really high to really low densities, every 3-5 years (see Lemmings). Arctic Fox - Renard arctique © Gilles Gauthier


When lemmings are abundant, Arctic Foxes can survive by mainly feeding on them, but in period of low lemming densities, foxes have to put more effort in preying upon alternative preys such as goose eggs and goslings. Since geese fiercely defend their nests against predators, catching eggs and goslings is however a more difficult and risky task than catching lemmings.

Even though Bylot Island Arctic Foxes can rely on alternative preys when there are few lemmings, their population remains largely driven by lemming abundance. In fact, fox reproductive effort (number and size of litters) seems to be closely related to lemming availability. In years following high peaks in lemming populations, foxes are in better physical condition, so many fox litters are found and the number of pups in each litter is high. In contrary, in years following very low lemming abundance, only few litters are found and litter sizes are small.

fox den - tanière de renard © Gilles Gauthier

Understanding Arctic Fox populations as been an important part of the Bylot Island ecological monitoring project. Every year since 1993, Arctic Fox breeding activity has been monitored. This is done by searching and monitoring Arctic Fox dens in the Qarlikturvik Valley as well as in the vicinity of the goose nesting colony (30 km south of Qarlikturvik Valley). Each year, all known dens (51 in 2002) are visited at least once, in late June or early July, to identify traces of fox activity. Dens that have shown activity signs are then visited later in the summer to determine the presence and number of fox in each litter. During these visits, the presence of Red Foxes has been observed. Therefore, their breeding activity has also been incorporated in our fox monitoring program.


From 1996 to 2000, relationships between Arctic Foxes, lemmings and geese were more thoroughly investigated. As a result, many questions related to the impact of Arctic Fox predation on Bylot Island Greater Snow Geese population were elucidated.

During the summer 2003, the den survey and monitoring was also expanded to an area covering 600 km². This allowed us to increase our number of know dens to a total of 98 (48 more than in 2002). Some of the foxes observed were captured and marked with collar emitting radio frequencies, which alllows us to study fox activity and diet around dens.

Arctic Fox stealing a goose egg - Renard arctique volant un oeuf d'oie © Joël Bêty



Relation Between Lemming Abundance and Fox Breeding Activity

As it was previously mentioned, the breeding effort of Arctic and Red Foxes seems to be closely related to lemming abundance. However, since the expansion of our den monitoring area in 2003, this relationship seems less visible and little is known yet about the lemming abundance in these new areas. It may be different or non-synchronized with that observed in the traditionally surveyed areas (see Lemmings).


Fox Denning Activity

The percentage of known dens that present signs of activity (either diggings or fresh prey remains) greatly vary from year to year and can be considered as an indicator of fox abundance. However, the variability of reproductive foxes is not similar but may be explained by the cyclic nature of lemming populations. Years with the lowest percentages of dens with pups are years when lemming abundance was the lowest as well.