Hamburg  - Sleepy sloths in steamy jungles are not nearly as sleepy and slothful as is commonly believed, according to a team of German researchers.

In fact, wild sloths are actually quite mentally alert and active, compared to sedentary zoo sloths. They only give the impression of being as lazy as city zoo sloths, the scientists from Germany's Max Planck Institute say.

In the first experiment to record the electro-physiology of sleep in a wild animal, three-toed sloths carrying miniature electroencephalogram recorders slept 9.63 hours per day - six hours less than captive sloths did, reports an international team of researchers working on the Smithsonian Tropical Research Institute's Barro Colorado Island in Panama.

"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," says the report's author, Dr. Niels Rattenborg, head of the Sleep and Flight Group at the Max Planck Institute for Ornithology.

"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," he adds.

Fortunately for the researchers, brown-throated three-toed sloths living in rainforest trees are not exactly fleet-footed creatures. So it was relatively easy for Rattenborg and his fellow scientists to catch them and put electronic monitors on their bodies.

The researchers lifted three adult female Bradypus variegatus out of their trees on Barro Colorado Island. Each lady sloth got a recorder glued to the hair on her head.

Fortunately for the German scientists, there was little chance that the sloths might bother to remove the monitors, being the lazy sloths that they are.

"Sloths are not known for grooming their hair," Rattenborg said.

Then the animals were freed to climb back up the trees.

The monitors did the rest of the work. Rattenborg and his colleagues utilised a revolutionary new, battery-operated, miniaturized EEG and EMG recorder weighing only 11 grams.

Small enough for animals to wear, the device allows monitoring of electrical impulses from the brain, but in the wild.

"This is the first step out of the laboratory," Rattenborg says in comments reported in Science News magazine.

Three to five days later, the researchers retrieved the devices and checked the results, which they report in an upcoming Biology Letters.

The sloths displayed no obvious signs of stress from having recorders glued to their heads, Rattenborg says.

After a day, their behaviour stabilized. And they even showed REM sleep patterns for about 20 per cent of the time, much like people.

Also, the recorders picked up signs of brain activity involved in sloths chewing leaves. Even when the brain wave patterns indicated sleep, the sloths made mild chewing motions.

"If they dream, I think they're dreaming about eating leaves," Science News quotes Rattenborg as saying. (dpa)