Sloths spend most of their lives in the tops of trees, as do many other mammals since it allows them to avoid predators, which prey along the ground. However, unlike many other mammals, sloths move incredibly slowly and sleep up to 20 hours a day. Due to their slow movements and need for a lot of sleep, sloths are both nocturnal and diurnal, meaning they are active during the day and night. Also, sloths move so slowly that algae grows on their fur. This helps the sloth to blend in with the trunks and branches of the trees they live in, but shows just how sedentary the sloth truly is.
Unlike other arboreal mammals, sloths hang from branches and move around upside-down. They even search for food and eat while upside down. This leads to one of the physical attributes that differentiates sloths from most other mammals; the direction of their hair growth. Sloth's hair, unlike most other mammals' hair, points downward from their stomach to their back. This helps sloths shed rain from their fur while in an upside down position.
Unlike other mammals, the sedentary sloths have extra neck vertebrae that allow them to turn their heads 270 degrees. This aids the sloths to see all around them while up in the trees, giving them an advantage when finding food. Since sloths move so slowly, the ability to find food without moving much is essential for survival. Once they spot their meal, usually leaves and bugs, they can move toward the food slowly but surely.
Sloths have low and unstable body temperatures and have difficulty self-regulating their body temperatures. Their body temperatures are normally lower than those of most other mammals. The body temperature of a sloth is greatly affected by the temperature of its surroundings, which keeps the sloths confined to tropical habitats. This lower body temperature also stems from the fact that the muscles of a sloth only account for 25 to 30 percent of its overall weight, according a study by the San Francisco University Department of Geography. The same study reports that reduced muscle mass determines the sloth's metabolism; sloths convert food into energy much more slowly than other species of the same size. This, the study goes on to say, causes nerves and muscles to function and respond to brain cues more slowly too, accounting for the sloth's slow movements.