Karrak Lake Arctic Fox Project

Results

We have captured and marked 135 adult foxes in 2000-2012 and 171 juvenile foxes in 2000-2007. Fifty-eight of these foxes have been encountered at Karrak Lake one or more years after their first capture (45 of which were marked as adults and 13 of which were marked as juveniles). In addition to foxes encountered at Karrak Lake, two foxes have been encountered in Resolute Bay on Cornwallis Island ca 850 km north of Karrak Lake (one subadult male and one subadult female that were both marked as pups at Karrak Lake in 2000), one fox has been encountered in Coppermine ca 600 km west of Karrak Lake (a subadult female that was marked as a pup at Karrak Lake in 2004), one fox has been encountered in Taloyoak ca 400 km northeast of Karrak Lake (an adult male that was marked as an adult in 2010), and one fox (identity unknown) has been seen at Cambridge Bay ca 300 km northwest of Karrak Lake.

Goose eggs were by far the most common food item taken by arctic foxes at Karrak Lake and made up 93% of all foods taken by foxes during the nesting season by geese. Other foods included lemmings, voles, geese, and eggs and young from passerine nests. Arctic foxes took, on average, 13, 8, and 12 eggs per hour during the nesting season in 2001-2003, respectively. Most eggs (96%) were cached for future use whereas most lemmings, voles, and geese (75%) were brought to den sites for consumption by young (only 8% of these foods were cached for future use). Foraging patterns of arctic foxes at Karrak Lake were similar to those at other large waterfowl nesting areas, although foxes at Karrak Lake took eggs at a faster rate than that at other large waterfowl nesting areas. See Samelius and Alisauskas (2000) for more detail on foraging behaviours of arctic foxes at large waterfowl nesting areas (see Publications for complete reference).

Nikita in summer of 2004

Arctic foxes took and cached 2,000-3,000 eggs per fox each year and the rate at which they took eggs was largely unrelated to individual attributes of foxes (e.g. sex, size, and breeding status) and nesting distribution of geese. Further, the rate at which foxes took eggs varied considerably within individuals in that foxes were efficient at taking eggs at times and inefficient at other times. This may have resulted from foxes switching between foraging actively and taking eggs opportunistically while performing other demands such as territorial behaviours.

Comparison of stable isotope ratios of fox tissues and those of their foods showed that the contribution of cached eggs to arctic fox diets was inversely related to collared lemming abundance. In fact, the contribution of cached eggs to overall fox diets increased from <28% in years when collared lemmings were abundant to 30-74% in years when collared lemmings were scarce. Further, arctic foxes used cached eggs well into the following spring (almost 1 year after eggs were acquired) – a pattern which differs from that of carnivores generally storing foods for only a few days before consumption. See Samelius et al. (2007) for more details on the extent at which arctic foxes used cached eggs (see Publications for complete reference).

Bigshooter in summer fur

Comparisons of reproduction and abundance of arctic foxes inside and outside the goose colony at Karrak Lake showed that (1) breeding density and fox abundance were 2-3 times higher inside the colony than they were outside the colony and (2) litter size, breeding density, and annual variation in fox abundance followed that of small mammal abundance. Small mammal abundance was, thus, the main governor of population dynamics of arctic foxes whereas geese and their eggs elevated fox abundance and breeding density above that which small mammals could support. These results highlight both the influence of seasonal and annual variation in food abundance on population dynamics of consumers and the linkage between arctic environments and wintering areas by geese thousands of kilometers to the south. See Samelius et al. (2011) for more information on the importance of seasonal and annual variation in food abundance on population dynamics of arctic foxes (see Publications for complete reference).

One den in 2000 was occupied by both foxes and wolves at the same time. Foxes and wolves used separate entrances and did not appear to share a common space. We don't know for how long they shared the den, but we saw evidence of both animals using the den in May and we saw both pups and adults of both species at the den at the same time in July. We have seen evidence of wolves using fox dens at two other occasions (1994 and 2001) but this occurred when there were no foxes breeding at these dens. See Hendrickson et al. (2005) for more details on foxes and wolves using the den at the same time (see Publications for complete reference).

Chris at the wolf entrance

This page was developed by Gustaf Samelius who also took the pictures