Climate change affecting Finland’s Arctic hares

Mountain hare. ( YLE / Vihtori Koskinen)
Mountain hare. ( YLE / Vihtori Koskinen)
When you see a hare in Finland, it’s likely to be a brown hare, also known as a European hare (Lepus europaeus).

This second of the country’s two native hare species is shouldering out its smaller relative, the mountain hare. Also called the Arctic or tundra hare, it is becoming rarer, especially in Southern Finland – partly as a result of climate change.

As its Latin name, Lepus timidus, suggests, the mountain hare is shyer. It is having a hard time standing its ground against the advance of the huskier, more aggressive brown hare.

While hare populations are subject to major annual fluctuations, the mountain hare population in Southern Finland has suffered a permanent drop of about half over the past two decades. The main reason, say researchers, is that winters have become shorter.

White fur no good on grass

“If you think about the mountain hare’s white winter coat, it doesn’t get any benefit from it when there’s no snow,” says Jaakko Pohjoismäki, a Research fellow in Genetics at the University of Eastern Finland in Joensuu.

“The same goes for its wide paws, which are suited to running over deep snow. Similar population declines were seen elsewhere in Europe after the last Ice Age, for instance.”

Pohjoismäki says that the brown hare’s role in the disappearance of the mountain hare is an interesting field for research: “Is this a natural replacement of one species by another as conditions change, or is it a question of the more aggressive brown hare’s surge forward as its own conditions improve?”

Big brown grabs food and females

Brown hares are spreading further north, partly because their heftier size gives them an advantage in the food queue.

“Generally brown hares are able to take more advantage of game feeding stations set up by hunting groups than the mountain hares,” Pohjoismäki notes.

Brown males also have an edge during mating season, which leads to cross-breeding between the two species.

“The male brown bucks are able to mate with the mountain hare does before the mountain males do. Here again, size may matter,” Pohjoismäki says.

As the species mingle, the mountain hares’ gene pool diminishes, and it may suffer otherwise, too.

“Brown hares may be slightly more resistant to infectious diseases or parasites than mountain hares. And the brown hare may carry pathogens that are more harmful to the mountain hare than to themselves,” he speculates.

In order to study the interbreeding of the two populations, Pohjoismäki aims to collect 1,000 frozen hare ears. By analysing these, he hopes to determine how much mingling has taken place. He hopes then to equip hares with GPS collars to track their movements.

In the meantime, the only rabbits found in the wild in Finland are feral. These escaped pets and their descendents have so far mostly seen in the Helsinki area.

Yle News

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