Sloths may make slow-motion replays look positively nippy but their reputation for slothfulness has been wildly exaggerated, scientists have found.

The South American mammal, with its sleepy-eyed face and apparently laid-back approach to life, spends far less time asleep and inactive than has been presumed. Although it has become a byword for laziness, researchers now argue that the sloth has been unfairly maligned.

Miniaturised electroencephalogram (EEG) tags fitted to wild sloths showed that instead of sleeping for almost 16 in every 24 hours they actually dozed off for just over 9½ only 9.63 hours. each day. They still moved around the forest canopy extremely slowly, but they were active for at least six hours more than expected.

The discovery was made possible by the tags, which allowed scientists to monitor the sleep patterns of sloths in their natural environment for the first time.

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Sleeping time had previously been measured using captive sloths, which, the researchers now realise, gave an inaccurate picture of their wakefulness in the wild. “Our results suggest that sleep in the wild may be markedly different from that in captivity,” the international research team reported in the journal Biology Letters.

Niels Rattenborg, of the Max Planck Institute for Ornithology in Germany, said that the discovery was expected to lead to fresh insights into the importance of sleep for a variety of animals, including people.

“We are fascinated that some species sleep far longer than others. If we can determine the reasons for variations in sleep patterns, we will gain insight into the function of sleep in mammals, including humans,” he said. “If animals behave differently in captivity — where all previous comparative studies were performed — than they do in the wild, measuring their brain activity in captivity can lead to the wrong conclusions.”

Roland Keys, of the New York State Museum in the US, one of the researchers, said that wild sloths were likely to sleep less because they had a harder life in which they had to find food and avoid predators. Captive animals, by contract, are guaranteed food and security.

“Sloths in captivity don’t really have anything to do so we weren’t surprised that they sleep more,” he said. “However, the six-hour difference was surprising.

“This was more than an extra little siesta in the middle of the day, and has real implications for our understanding of sleep in all animals.”

The study, using brown-throated three-toed sloths, Bradypus variegatus, was carried out on the Smithsonian Tropical Research Institute’s Barro Colorado Island in Panama.

Tai Strike, a veterinary officer for the Zoological Society of London, said that recent observations of sloths at London Zoo had led keepers to reach a similar conclusion to the research team. She said that the extra hours the animals spent asleep in captivity could be a result of boredom.

It had been thought that sloths were so inactive that all they needed in captivity was somewhere to hang. Since opening an open-plan rainforest facility at the zoo where the animals can roam more extensively it has been seen that the activity levels of the sloths has increased sharply.

“It’s been amazing how active they are,” she said. “People used to think that all sloths needed was a tree to hang from to keep them happy — you didn’t need to make space for them to use like you would for a gibbon. We’ve found the opposite to be true. By giving them more space and an interesting environment they are incredibly active compared to what they were.”

Hanging Out - the facts about sloths

— The sloth is descended from a family of mammals that appeared on earth about 60 million years ago

— There are six species of sloth alive today

— They are found in the rainforests of Central and South America

— Giant ground sloths, now extinct, could rear up as high as giraffes and weighed as much as a mammoth

— Sloths mate and give birth while suspended from branches

— They spend most of their lives in the forest canopy, but descend from the trees to go to the loo

— The three-toed sloth can take a minute to travel two metres

— They turn green because algae grows on them

— Meals may take a month to digest. Leaves form the bulk of their diet although they may eat insects

— In the wild they can live for 12 years but in captivity they have exceeded 30 years

— Oviedo y Valdes, a Spaniard who saw sloths during the sixteenth century, described them as the ugliest and most useless animals that he had ever encountered

Source: Times database

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