Munich - Sloths, the slowest-moving, sleepiest mammals in most zoos, are perkier in their South American jungle homes, getting through each day with only an average 9.6 hours of sleep, scientists have discovered.

Reseachers attached an electro-encephalogram (EEG) recorder to several brown-throated three-toed sloths, scientific name Bradypus variegatus, as they spent their days very slowly munching on leaves.

The team, led by Niels Rattenborg of the Max Planck Ornithology Institute in Germany, made the surprising discovery that zoo sloths sleep more than six hours longer than their wild relations.

"If we can discover the reason for the difference, we'll gain an insight into the function of sleep in mammals generally, including people," said Rattenborg, who joined with staff of the Smithsonian Tropical Research Institutes in Panama in the study.

The slow animals live in the jungle canopy, 40 metres above the ground, in Panama.

The findings appeared in the Biology Letters published in London by the Royal Society. (dpa)