Seemingly being propelled north by warming temperatures ...........Red Foxes are becoming more prevalent in Hudson Bay, Canada as Arctic Foxes become less and less seen on the landscape..............The Red Foxes seem to be more aggressive than the Arctic Foxes and are capable of driving them out of their historical habitat................However, will winter weather slow down their immigration into the Arctic?

Arctic foxes suffer

 while reds thrive

 in northern Canada

bbc.co.uk

And, unusually, the number of red foxes has
 simultaneously surged in the area, on Hudson
 Bay.Arctic fox sightings in northern Canada are
 at an unprecedented low this winter, according
 to wildlife guides.

The surprising pattern has prompted observers to
 question whether the elusive Arctic foxes are being
 driven out of their dens by invading red relatives.

"It stopped dead, turned and ran," says Tera Ryan,
 wildlife guide at polar expedition company Churchill Wild,
 describing the time she witnessed an Arctic fox's reaction
 to a red fox travelling away in the distance.

"In the Arctic you conserve energy... This was running for fear. He did not want to be seen by that red fox."

Famed for their bright white coats in winter, delicate
 Arctic foxes (Vulpes lagopus) are not much larger
 than a domestic cat. Yet with their thick, insulating
 fur and increased blood circulation they are adapted 
to thrive in some of the world's most extreme conditions.

Previous studies have indicated that larger and more
aggressive red foxes moving northward may outcompete
their Arctic cousins for food and even kill the smaller
 species when the two collide on the same territory.

Arctic fox populations naturally fluctuate from year to
 year depending on the availability of their main food
 source, lemmings.

But the wildlife guides at Seal River lodge on Hudson
 Bay have reported the lowest number of Arctic fox
 sightings for years, despite what they say is a good
 year for lemmings.

The team have reported an average of two Arctic foxes
spotted near their observation lodge in the same day,
 whereas "it would not be unusual to see a dozen or
 more per day in an average year," says Churchill
 Wild's Mike Reimer.

"Last year we had Arctic foxes everywhere you looked
 and no coloured foxes. And this year is completely
different.

"This year it's coloured foxes... we've got red, silvers
, crosses. And we've had the odd Arctic fox try to come
 in and the coloured [ones] are much more aggressiv
e so they drive them off."Dr Roth's annual
 observations of both Arctic and red fox
 dens around the Arctic town of Churchill
 show that the success of the two species is highly
correlated.red foxes may struggle in cold weather 

But biologist Dr Jim Roth from the University of Manitoba in Winnipeg, Canada says that while it is "possible" a surge in red foxes this season could have a temporary impact on Arctic fox numbers, the dip is more likely to have been caused by another factor such as food resources, disease or parasites.

"However, in 2011 Arctic fox den success was among the lowest ever recorded, while red fox den was among the highest," he says.

Dr Roth concluded that a different prey species such as snowshoe hare may have been abundant in red foxes' forest habitat but was not available to Arctic foxes hunting on the tundra terrain.

Despite this evidence, some experts believe that red foxes gradually moving further north are a major threat to Arctic foxes.

A red fox seamlessly squeezes through a wire fence in Arctic Canada

.In Russia, reds have been observed taking over Arctic
 fox dens and scientists have occasionally found Arctic
 fox remains around some red fox dens.

"Being bigger, the red fox tends to exclude the Arctic
 fox from its habitat," explains Dr Dominique Berteaux
from the University of Quebec, Rimouski (UQAR) in
 Canada.

"They occupy the same ecological niche and are
in direct competition."

However, Dr Roth argues that in general, "changes
in food availability and disease" are "more likely to
 have greater impacts" on Arctic fox numbers.

The change in red fox distribution, with the species
 pushing further northwards, has been associated
with climate change in the Arctic.

Warmer conditions allow red foxes to travel further
 north as they are more likely to survive without
 the special adaptations of the Arctic species.

But Dr Berteaux, who has conducted a number
of studies into Canada's Arctic foxes, believes
we may actually be more directly accountable
for the species' movement.

"Red foxes follow humans," he tells BBC Nature.

"In the last 60 years many villages have established
 in the Arctic and red fox benefit from the dump
sites where they scavenge on human garbage."

Dr Bertaux simply summarises that the red foxes
"have more food available now than in the past"
but his fellow biologists continue to debate the issue.