When food is precious, animals can resort to strange behaviours in order to satisfy their hunger. Take the great tit. Its usual diet of insects and creepy-crawlies is harder to come by in winter. But in one Hungarian cave, great tits, ever the opportunists, have learned to exploit a rich and unusual source of food. They kill sleeping bats.

Great tits are only about 5 inches long, but their prey – the pipistrelle bat – is smaller still, just an inch or two in size. The bats spend the winter months hibernating in rock crevices. They’re well hidden, but when they wake up, they start making noises and these are the telltale signs that the birds are listening out for. They