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Round Island Foxes

By Margaret Archibald

Red foxes are one of the special guest stars on the explore.org “walrus cam” where their cameos are often caught by sharp-eyed viewers as they tiptoe between the slumbering masses of walrus. The Red fox (Vulpes vulpes) is both the largest land mammal and the largest land predator on Round Island. The role foxes play in the island ecosystem is both unique and essential to the interlocking community of species here. Red foxes are one of the world’s most widespread and adaptable land carnivores, they live and thrive from deserts to tundra, from forests to fields and suburbs all over the northern hemisphere. In each habitat that red foxes turn up, they adapt to fill a unique niche in their ecosystem. On Round Island their diets, foraging strategy and social structures have been adapted and perfected over time to make the most of their isolated island existence.

Although foxes were historically  introduced to many islands in Alaska for the purpose of fur farming- in many cases with tragic consequences for local fauna- the foxes on Round Island are most likely ‘native’, and the delicately balanced community of species on the island has grown up around them. It is hard to say how long the foxes have been here, but it is likely that at a few times, in the 11,000 years since the last period of glaciation ended and Alaska gained its current shape and coastline, an adventurous pair of foxes took advantage of an icy winter to venture out across the 12 miles from mainland to this snow-capped bump on the frozen sea. Perhaps that first winter they found a thawing walrus carcass, or a boom-year population of voles and lemmings to support them. Whatever it was, they hit the jackpot with the absolute seabird bonanza that arrived in the spring. Those first foxes took good advantage of the island’s bounty that summer, and before long the island was supporting a whole population of foxes. Today, the fox population on Round Island can be 10 times as dense as populations on mainland. Foxes on the island have adapted diets, social structures and foraging techniques that allow them to stay here and thrive through both the bountiful summers and cold, lean winters. Specialists in cliff-climbing and seabird hunting, foxes on Round Island have no real predators and their population is controlled only by winter food supply and social hierarchies.  They do not exactly have territories; instead they share a loose conglomeration of overlapping home ranges. With the exception of the areas in the immediate vicinity of active dens, home ranges are porous and not necessarily defended from intrusion. On the mainland, a typical fox might have a range territory of  5 to 12 square kilometers whereas on Round Island which is just a little over 3 square kilometers total there can be upwards of 5 or 6 active dens in a good year. Each den consists of one breeding female, one male and one or more relatives that act as helpers to bring seabirds, eggs and food to a litter of anywhere from 2 to 8 kits. In particularly bountiful years a male fox may support two dens or two mothers in the same den, but it is not clear that all the kits share the same odds for survival. While it might sound like the island would quickly be overrun with so many dens and so many kits, red foxes typically live only 3 to 5 years and on Round Island it is thought that, due to social and nutritional pressure, fewer than 30% of the foxes that survive to one year of age will ever attempt to reproduce. Moreover, because the foxes survive largely on rodent and seabird populations that are subject to boom and bust cycles of abundance, a bad year for seabirds, can quickly become a bad year for foxes where only the very strongest and wilyest survive the lean winter to breed again.

Round Island foxes, due to their dense population and having no experience of predation, are famous for their unconcerned attitudes towards human beings. They nap openly on sun warmed hillsides without fear of attack or predation and it is possible to stumble-upon and nearly step on one, only to have it sit up awake at the last moment -startling you out of your skin- just to give you the withering glare of one who’s nap has been interrupted, stretch its legs, and then lie back down. Any human who visits or stays on the island quickly becomes accustomed to the strange feeling of being watched or followed -when they turn around and discover a trotting red fox at their heels. Likewise, the rascals justify that funny feeling that you’ve left your gloves, hat, or gopro just… there…. but then of not being able to find them -because a pesky canid has just left with them. The foxes are habituated to human presence but not conditioned to seek out human food as we are very careful to never give them access to this artificial resource.  Instead they spend their summer months making daring trips along the steep, rocky cliffs and beaches gathering and delicately transporting seabird eggs and chicks to feed to their kits and to hide in the tundra for winter use. In winter the foxes must hunt under the snow to find their summer stashes and the secretive trails of the islands rodents, or patiently scour the beaches for wintering sea ducks, marine casualties and other offerings from the tides. I often find myself wondering how this little island can harbor enough hidden calories to keep them going through the winters, but with luck and persistence, for as long as humans have been coming to Round Island and writing reports about it, they have been met each spring by the resilient foxes, curious and long-coated, apparently healthy and preparing for the next season of kits and cliffs, eggs and campers.

The next time someone catches a quick snap of one of our wily red friends looking so delicate amongst the walrus on the cam, think of them, like I do, midwinter, holding down the fort, long since left behind by the migrant walrus, and the majority of the birds. They are persistent and adaptable, the true royalty of the snow shrouded island, waiting with dignity, for spring, with its feasts and wonders and to return. And for us of course, to trim the grass along the trails for them.


Sources Cited

 Jennings L. 2008. Red Fox. Alaska Department of Fish and Game, http://www.adfg.alaska.gov/. Juneau, Alaska. http://www.adfg.alaska.gov/static/education/wns/red_fox.pdf

Zabel CJ, 1989. Shift in red fox, Vulpes vulpes, mating system associated with El Niño in the Bering Sea. Animal Behavior, 38, 830-838

Zabel CJ, 1986. Reproductive Behavior of the Red Fox (Vulpes vulpes): A Longitudinal Study of an Island Population. Dissertation Submitted. University of California, Santa Cruz.