“Baby sloths SQUEAK, adult sloths are much less verbal, typically only HISSING if they’re THREATENED.”
National Geographic Kids, 5,000 Awesome Facts, fact 21 on sloths
There are actually several discreet sounds that sloths do use. Some of these sounds includes high pitched squeaks or whistles when they are trying to communicate with other sloths, or if they are in distress.
Grunts and snorts occur if they are experiencing discomfort or some sort of annoyance.
A hissing sound means they are feeling threatened, and is more of a defensive call.
Sloths actually purr like a cat when they are content and comfortable in their surroundings.
Squealing comes from the infant sloths trying to maintain contact with their mothers.
However, the sounds between 3 toed and 2 toed baby sloths vary. The 3 toed sloths make a high pitched squeak whereas the 2 toed sloths sound like the bleating of baby goats. Even as adults the 2 toed and 3 toed have different vocalizations.
Usually the sounds emitted from sloths are very soft and subtle, making it hard for humans to hear. Sloths are not known for their vocal qualities. They do not make noises when they move, and they are very obscure in the trees that scientists are not quite sure what all sounds they make and what they may mean.
Sources:
animalfieldguide.com
CHARLEY WAFFLE 