Vulpes lagopus the Arctic Fox
Figure 1: Arctic fox (Vulpes
lagopus)
The Arctic fox (Vulpes (Alopex) lagopus) only recently evolved,
roughly 0.5 million years ago (Macdonald, 2009). V. lagopus is found in all arctic tundra habitats, from seashore to
sea ice and in most islands of Northern Eurasia, North America, Greenland and
Iceland (Figure 2) (Macdonald, 2009; Nowak, 1999).
To
adapt to its environment this fox has two dichromatic colour forms. This
includes a “white” fur coat, which is pure white to a grey brown in the summer.
However, individuals in a less severe climate tend to remain fairly dark
throughout the year. Individuals with the “blue” colouration are a pale blue grey
in winter and a dark blue grey in the summer (Macdonald, 2009; Nowak, 1999). This
“blue” colouration constitutes 1% of the arctic fox population of mainland
Canada, less than 5% of that of Baffin Island, 50% of Greenland and most of the
Icelandic population (Nowak, 1999). A reason for this distribution of the two
fur colourations is suggested to be for the increased camouflage value it
offered to individuals in coastal areas. Thus, giving this species an advantage
in such a harsh climate.
As well as added camouflage, the
coats of these foxes can increase up to 200% in depth in winter to keep them
warm (Nowak, 1999). Arctic foxes also have an increased blood flow to a
capillary rete on the skin of the pad, to keep their paws from freezing. It is
also suggested that they may have a counter current vascular exchange mechanism
to avoid heat loss when warm blood flows into the legs (Nowak, 1999). These adaptations to the cold environment are
ultimately what give this fox the ability to survive in such hard environment
and climatic conditions. 
That’s awesome that they have basically heated foot pads Do these animals show other physiological adaptations, such as torpor or hibernation to combat low food and water availability? What do they eat?
ReplyDeleteStudies have found that there is no seasonal variation in the basal metabolic rate (BMR)of the arctic fox. However, measurements indicate an unusually large reduction in the BMR of starving foxes, and their food intake seems to be voluntarily reduced periodically (Prestrud, 1991). Arctic foxes are known to follow larger predators for days for any chance at scavenging leftovers. Their diet consists of sea birds, ptarmigan, shore invertebrates, fruit, and berries, together with any remains found (Macdonald, 2009).
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