From Nature:
The average day of the average sloth isn’t so different from yours or mine, it seems. It goes something like this: 8 a.m.: wake up; 6 p.m.: dinner; 11 p.m.: bed.
Although that schedule doesn’t sound too hectic, it is a lot more activity than was previously expected from sloths. Studies of captive sloths had suggested that the animals slept for almost 16 hours a day. But the first recordings of brain activity from wild animals show that the actual figure is less than 10 hours. “I was astonished — I expected minor differences, but six hours a day is a very big difference,” says the study’s lead author, Niels Rattenborg of the Max Planck Institute for Ornithology in Starnberg, Germany. The finding shows that the amount that animals sleep in the lab might not reflect how much shut-eye they get in the wild. And it suggests that comparisons of the sleeping patterns of different species need to take into account many different behaviours and environmental factors.
More here.