War Of The Foxes: The Story of The Arctic Invasion

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Winner of The 2015 Wildlife Photographer of the year, “A Tale of Two Foxes” copyright Don Gutoski

The beautifully chilling “Tale of Two Foxes” by Don Gutoski recently scooped the coveted Wildlife Photographer of the Year 2015 Grand Prize and now sits pride of place among the other finalists in the Natural History Museum in London.  This thought-provoking photo tells a story of the ever-growing threat of climate change through the eyes of the emerging conflict between Red and Arctic foxes as the former expands its range northward in warming Arctic temperatures.

The IPCC (Intergovernmental Panel on Climate Change) predicts that global temperatures could rise by up to 4.8°C by the end of the century and identifies that these warming trends will happen much more rapidly in the Arctic region. With this in mind, it is far more likely that many species will be moving northward to stay within their optimum temperature and habitat range, perhaps permanently altering the dynamics of Arctic ecosystems [1].

The Red Fox Invasion
The Arctic fox (Alopex lagopus) is found in tundra habitats throughout the Arctic Circle. Although it is generally thought to have a favourable conservation status, in some areas of its distribution populations are now reaching critically low levels. In Fennoscandia (The area of Scandinavian Arctic comprising of Norway, Finland, Sweden and parts of Russia) Arctic fox numbers are thought to be as low as 120 individuals.

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Arctic Fox, source: public domain

Even though the Arctic fox has been protected in this area for more than 70 years, numbers have remained extremely low. This lack of recovery is now thought to be down to the invasion of the Red fox (Vulpes vulpes) [2]. The Red fox is much larger than the Arctic fox (5.5kg on average, compared to 3.5kg) and therefore can out-compete Arctic foxes for food sources such as lemmings, on which Arctic foxes heavily rely [2]. They are also able to physically dominate their smaller counterparts and have been known to prey upon Arctic fox litters [3] and can even hunt adults too; a behaviour observed for one of the first times in Don Gutoski’s “Tale of Two Foxes”.

Research into the failed recovery of Arctic foxes in Fennoscandia found that Arctic foxes were absent in all sites where Reds were found, and were only seen to recolonize areas in which Red foxes had been removed by experimental culls [2]. In fact, Red fox presence was found to be the main factor limiting Arctic fox distribution, and was more important than human disturbance or even limited food supplies [2]. This suggests that as Red fox populations expand and encroach upon Arctic fox territories, Arctic foxes will be forced to retreat further and further north until there is nowhere left to go.

It’s not just in Fennoscandia that this is a problem.  Recent studies in the Alaskan Arctic have discovered a huge turnover of den sites from Arctic fox to Red fox habitation [3]. In 2005, 85% of dens in the study site were occupied by Arctic foxes but by 2011 it was Red foxes who inhabited   83% of dens (Figure 1) [3].Once a den was vacated by an Arctic fox in favour of a Red fox, it never returned [3].

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Figure 1. Number of dens occupied by Red and Arctic foxes in Prudoe Bay, Alaska from 2005-2011 [3]

As expected due to their success in urban environments, Red foxes in the Arctic are particularly successful around areas of human activity, such as the oil fields of Alaska. Their ability to exploit multiple food sources means they are a lot more versatile than the heavily lemming-dependent Arctic fox [3]. Worryingly, if possible plans to expand oil drilling in Alaska go ahead then Arctic foxes could be at further risk of being out-competed.

Shifting Arctic Communities
While the Red fox may be the poster child for the great Arctic invasion, the truth is poleward migration is happening on a much larger scale. For example, a large number of insect species are now expanding their ranges in the face of climate change; critically, many of these are pests [4].  Two moth species Operophtera brumata and Epirrita autumnata normally limited in range by egg death at cold Arctic temperatures are now being found much further north [4]. Outbreaks of these leaf-eating moths cause dramatic defoliation (large loss of leaf coverage) (Figure 2), decreasing tree growth and in severe cases causing large areas of forest death [4]. Unfortunately, climate change is also increasing the frequency of these deadly outbreaks and so the northward migration of these pests could have severe impacts on the subarctic birch forests and the species that live there.

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Figure 2. Northward migration of herbivores such as the winter moth (inset) in Scandinavia. Healthy areas of woodland are shown in green and areas of severe defoliation associated with outbreaks from 2005-2008 in brown.  Yellow dots show locations of earlier outbreaks.[1]

In the Arctic seas surrounding the pole, communities are also changing. Atlantic and North Sea fish are migrating North at rates of up to 169km per decade and assessments of Arctic fish communities have found a huge shift in the species now making up Arctic ecosystems [5]. Large pelagic fish species like cod are moving North and competing with Arctic predators such as the Greenland halibut (Reinhardtius hippoglossoides) and reducing the abundance of smaller benthic fishes, vital to the Arctic food chain [5]. Not only will this impact the diet of Arctic marine organisms but it also has implications for commercial fisheries.

The Last Stand
In the face of a warming climate, Arctic specialists like the Arctic fox still have a stronghold in the harshest northern environments but they are now facing threats from advancing invaders who can often outcompete them. When compounded by other effects of climate change such as ice-cover depletion and threatened with human over exploitation, it is clear that for many Arctic species the battle to survive has only just begun.

 

References

  1. Post, E. et al. 2009 Ecological dynamics across the Arctic associated with recent climate change. Science 325, 1355–1358. (doi:10.1126/science.1173113)
  1. Hamel, S., Killengreen, S. T., Henden, J.-A., Yoccoz, N. G. & Ims, R. A. 2013 Disentangling the importance of interspecific competition, food availability, and habitat in species occupancy: Recolonization of the endangered Fennoscandian arctic fox. Biol. Conserv. 160, 114–120. (doi:10.1016/j.biocon.2013.01.011)
  1. Stickney, A. A., Obritschkewitsch, T. & Burgess, R. M. 2014 Shifts in fox den occupancy in the greater Prudhoe Bay area , Alaska. Arctic 67, 196–202. (doi:10.14430/arctic4386)
  1. Jepsen, J. U., Hagen, S. B., Ims, R. A. & Yoccoz, N. G. 2008 Climate change and outbreaks of the geometrids Operophtera brumata and Epirrita autumnata in subarctic birch forest: evidence of a recent outbreak range expansion. J. Anim. Ecol. 77, 257–264. (doi:10.1111/j.1365-2656.2007.0)
  1. Fossheim, M., Primicerio, R., Johannesen, E., Ingvaldsen, R. B., Aschan, M. M. & Dolgov, A. V. 2015 Recent warming leads to a rapid borealization of fish communities in the Arctic. Nat. Clim. Chang. 5, 673–677. (doi:10.1038/nclimate2647)
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