In Svalbard, the arctic fox is the apex terrestrial predator and scavenger with no natural enemies or competitors. It is abundant and functionally important - in particular in terms of its impacts on both terrestrial (ground nesting birds like ptarmigan and geese) and marine prey species (sea birds and the ringed seal). Svalbard lacks cyclically fluctuating arctic small rodents (like lemmings) so the population are much more stable compared to most other tundra ecosystems. Nevertheless, the arctic fox in Svalbard does show significant year-to-year variation in population size, however without any obvious long-term trends.
The population dynamics is to large extent proximately driven by the availability of reindeer carcasses and ultimately by rain-on-snow events causing increased reindeer mortality. Sea bird colonies provide a constant resource that acts to stabilize the arctic fox population. The future fate of arctic fox populations in Svalbard will depend on the impact of climate change on its main food resources - reindeer, geese and sea birds. The role of other marine subsidies such as seals, which depends on the extent of sea ice, is presently unknown.
Figure of arctic fox den occupancy rate (percentage of known dens with cubs) in the two monitoring areas in Svalbard (A. Kongsfjorden/Brøggerhalvøya and B. Adventdalen/Sassendalen).
Arctic foxes are vulnerable to disturbances specifically during the denning period from mid May to mid August (see AECOS wildlife guidelines).
Arctic foxes has traditionally been harvested for their fur in Svalbard, and traditional trapping is still conducted mainly as recreational activity by local people, but also as a commercial activity at few trapping stations.
The arctic fox in Svalbard is a reservoir for dangerous zoonoses (animal born parasite/diseases that may spillover to humans) in particular rabies and the tapeworm Echinococcus multilocularis (EM). Rabies in Svalbard has an irregular/infrequent outbreak dynamics and is probably not endemic in Svalbard. The prevalence of EM is much dependent on the distribution of the introduced sibling vole (Microtus levis), which is an obligate intermediate host for this parasite.
Expected climate impact
The impact of climate change on arctic foxes in Svalbard is indirect and likely to be mediated by several pathways.
Climate change is rapidly decreasing the extent of sea ice around Svalbard. This can have negative impacts on arctic fox since sea ice is an important platform, both for migration and acquisition of marine prey (ice-dependent sea birds and sea mammals). Warmer winters will also affect the availability of terrestrial resources, in particular the amount of reindeer carrion. Whether this effect on the long-term will be positive or negative is uncertain. Arctic breeding geese populations are presently increasing in Svalbard for both climatic and other reasons, and is expected to increase the prey availability in summer and thereby have a positive effect on arctic fox breeding success.
Changes in arctic fox population size, migration patterns and the dynamics of intermediate host of parasites are likely to affect the prevalence of zoonoses in Svalbard. Decreased extent of sea ice will cause less influx of rabid foxes from locations outside Svalbard (like Siberia). The prevalence of Echinococcus multilocularis will depend on the fate of the population of sibling voles in a warmer climate.
Expected effects of climate change and management decisions on arctic fox in Svalbard. The model predicts three climate impact paths. One works though decreased sea ice extents reducing arctic fox migration and exploitation of marine resources in winter. The two other pathways work indirectly though variable climate impact on availability of key terrestrial prey species, like reindeer and geese. All changes in arctic fox population density, movements as well intermediate hosts are likely to influence the prevalence of zoonoses (like rabies and Echinococcus multilocularis) in Svalbard.
- Information about the population size of the arctic fox is important for the Governor of Svalbard for making decisions about the harvesting levels. In the context of today’s rapid climate change, it is important to ensure that the harvesting level is sustainable in new climatic settings and to be able to mitigate the impact of arctic fox predation on vulnerable prey as the Svalbard rock ptarmigan. Since reindeer and geese are important food sources to arctic fox, their management must also be considered in context of arctic fox management.
- The function of the arctic fox as the key vector for rabies virus and EM in is of particular societal concern in Svalbard. While the outbreaks of rabies may become even rarer with the rabidly decreasing sea ice extent around Svalbard, EM may become more prevalent and widespread pending on an increased distribution of the sibling vole in a warming climate.
The breeding population of arctic fox is monitored in two areas West Spitsbergen by means of den surveys for (see Mosj and NPI): Six to 9 dens located over approximately 220 km2 in Kongsfjorden/Brøggerhalvøya have been surveyed since 1993, and up to 32 dens, over approximately 900 km2 in Sassendalen/Adventdalen have been surveyed over two time periods, between 1982 - 1989 and from 1997 and onward. These dens are visited every year (in late June to early August) and fox activity (presence of adult foxes and prey remains), number of pups (if the foxes are breeding) and disturbance from humans are recorded. This den monitoring are based on two methods:
- Observation by use of binoculars / telescope from set points, at a safe distance from the den not to disturb.
- Automatic cameras on dens.
Carcasses of trapped foxes are collected to obtain data on demographic parameters (size, age and reproduction) and tissues and organs are sampled for studies genetics, diets (stable isotopes), parasitology and eco-toxicology.
The sibling vole, which is the intermediate host for the zoonotic parasite Echinococcus multilocularis (which has the Arctic fox as determinate host), is monitored with system of camera traps in the Isfjorden area (see report, in Norwegian). This monitoring will yield knowledge about the population dynamics and geographic range of the sibling vole and thereby also the infection potential of the parasite.