Sloths, as their name betrays, have little need to rush. For the most part, they live high in the branches of the forests which stretch across Central and South America, only coming down to the ground to defecate. And the life they lead is very much in slow motion.

Just why sloths move so slowly is due to some peculiar evolutionary tricks.

Modern-day sloths – the three-toed sloth and the two-toed sloth – are much smaller versions of the sloths that inhabited the prehistoric world. Giant sloths, some that would weigh up to several tonnes, walked on the ground during the last ice age until around 11,000 years ago, foraging from the trees by standing up on their hind legs to reach into the foliage.

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“What changed was a combination of both going up into the trees, and having a diet almost entirely based on leaves,” says Camila Mazzoni of the Leibniz Institute for Zoo and Wildlife Research in Germany.

“The leaf diet is very poor in nutrients and the intake of calories is very low. Because of this they have to have a very slow metabolic rate to cope with this low calorific intake.”

And part of that comes down to where it is they live.