Animals massively postpone hibernation: what are the consequences?

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By mid-November at the latest, most hibernators normally lie in their comfortable den for a few months. But because it has only frozen once, the woods are still buzzing with activity. “Animals don’t feel like sleeping yet,” says Sil Janssen.

Mireille Maes

Hedgehogs walking around at night, squirrels still jumping from branch to branch, a brown-red heather dragonfly floating by. Due to the mild autumn there is still a lot to see in nature. “It has usually already frozen a few times in mid-October, early November and that is a trigger for most animals to go into hibernation. It’s mid-November and the temperature has only dropped below freezing once. The result: those animals don’t feel like going to sleep yet. We really notice that in the calls we receive,” says Sil Janssen.


That hibernation is not really necessary either. “Animals go into hibernation because there is no food left, but due to the mild temperatures there is still plenty of food. Berries, apples, snails, worms, the animals still have plenty of choice. Only when that stops will the hibernators go to their den.”

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Due to the warm autumn weather, some animal species have even taken the gamble to reproduce. “A few days ago I saw caterpillars of the Queen’s page. I’ve never seen it this late. Those caterpillars would have to eat a lot very quickly to pupate, but I fear that these specimens will not make it,” says Wim Veraghtert of Natuurpunt.

For other species, the mild autumn has not led to a revival anyway. “I am thinking of the peacock eye and the atalanta. At the end of July there were a lot of caterpillars. Only few of them are fully grown due to the hot summer. It is now difficult to say whether we will have fewer butterflies next year as a result. Some specimens are hopefully in a resting place and will not wake up until March next year,” says Veraghtert.


The specialists do not think that this late hibernation has any consequences for the animals. “A late hibernation seems to me to have few disadvantages. The animals are well fed. It is much worse when the animals are in full hibernation and then suddenly surprised by temperatures around 15 degrees. An interrupted hibernation can be detrimental. Then when frost comes, let it be all winter. Preferably until February,” concludes Veraghtert.

READ MORE. Why animals and insects prefer solid frost to a quail winter.

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