The arctic fox (vulpes lagopus) is a small fox found in the northern hemisphere. They live in cold climates and are well adapted to frigid environments. It’s a well-known fact about arctic foxes that they are white to blend in with the snowy white arctic landscape, but what happens to them in the summer when parts of the tundra melt? Do arctic foxes have a summer coat that changes color?
Yes, arctic foxes change the color of their fur depending on the season which makes it harder for predators to spot them. The arctic fox’s coat color will be white during winter months to blend in with the snow, then they will switch to earthy tones such as brown or grey during summer months.
Keep reading to find out why and how they change the color of their fur coat and some other adaptions they make to help them survive.
Do Arctic Foxes Change Color?
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Arctic foxes are best known for their thick white fur that helps them blend in with the snow of the arctic and ice floes. This provides camouflage to protect them from their predators.
However, as the snow melts in the warmer months of the year and they migrate to areas with less snowfall, they don’t keep their white fur as this would make them too obvious to predators.
Instead, in summer arctic foxes shed their white coat for more earthy tones such as brown, grey, or sometimes even red fur. This helps it camouflage against the vegetation and rocky terrain in the tundra and the edges of forests where they can be found in summer1 (source: National Geographic YouTube Channel).
As well as changing the color of their coat, they also change the thickness to help with insulation, but more on this later. The below image shows arctic fox summer vs winter coat.
However, one variant known as the blue morph arctic fox does not grow a white winter coat. Although it does still change color slightly, from a dark gray/blue coat in summer to a lighter gray coat in winter2 (source: PubMed, DI Våge, et al, 2005). The blue morph arctic fox is very rare with estimates putting the population of blue morphs between 1-3% of the total arctic fox population3 (source: Norwegian Polar Institue).
Most of the arctic animals you know will keep the color of their fur year-round such as the polar bear and snowy owls. However, arctic foxes aren’t alone in changing color between seasons. Both the arctic hare and the stoat have a white coat in winter to better camouflage against the snow4 (source: National Geographic).
How Do Arctic Foxes Change Color?
Seasonal molting occurs in around 21 different species from 5 families of birds and mammals and all work in a similar way whether it is feathers or fur.
The color variation is determined by melanin pigments which are responsible for giving arctic foxes their brown/grey color during summer5 (source: Italian Journal of Animal Science, J Bao, et al, Vol 14, Issue 3, 2015).
You’ll notice variations in the color of the arctic fox summer coat depending upon where they live. For example, those in wooded areas may have a red/brown summer coat whereas those in rocky areas may be more grey to help them blend in.
This is because there are two types of melanin pigment – eumelanin and phaeomelanin.
Eumelanin results in black/brown colors whereas phaeomelanin results in yellow/red colors. Arctic foxes in different areas will have a different ratio of the two which has evolved over time6 (source: Biological Reviews, M Zimova, et al, vol 93, Issue 3, Aug 2018).
When Do Arctic Foxes Change Color?
Arctic foxes molt their white winter coat around May in favor of their thinner brown/grey summer coat. This lasts them through the summer months until they begin growing their white winter coat again in September7 (source: PubMed, DI Våge, et al, 2005).
It can take several months for them to fully grow their winter coat and it may not reach full length until early December.
Why Do Arctic Foxes Have Thick Fur?
Arctic foxes have adapted to life in the extreme conditions of the arctic tundra by being able to live with little food and water, having thick fur for insulation, and white fur so they can blend into their surroundings. This means that arctic foxes do not need to hibernate or migrate.
Their winter fur is 200% thicker than their summer fur8 (source: PubMed, DI Våge, et al, 2005) and at a microscopic level contains more air which makes them more effective at keeping the fox warm.
There have been suggestions that the white fur loses less heat via radiation although this has never been proven9 (source: Biological Reviews, M Zimova, et al, vol 93, Issue 3, Aug 2018).
They also grow additional hair on their feet for better insulation and traction during snowy seasons, having lots of hair on their feet helps to prevent slipping as they race across the icy terrain10 (source: National Geographic).
Their thick busky tail is also useful for keeping warm in winter and similar to cats is used to help them maintain balance.
The Effect of Climate Change on Arctic Foxes
Climate change is having an impact on the habitat of the arctic, notably the melting of snow which has resulted in arctic foxes becoming endangered in some regions of Fennoscandia. This can result in a mismatch between the color of their winter coat and their surroundings.
This makes their camouflage less effective and can result in them becoming more susceptible to predators. It also has an impact on their ability to catch food as they use camouflage to sneak up on their prey. This is one of the reasons why red foxes are flourishing in areas previously dominated by arctic foxes11 (source: Climate Change Biology, L Hannah, 2011).
Scientists expect that arctic foxes will adapt the color of their winter coat over time (by natural selection) or may even lose their winter coat altogether12 (source: Biological Reviews, M Zimova, et al, vol 93, Issue 3, Aug 2018).
