Mammals: Two-toed Sloth

Range: Central America and South America Habitat: tropical forests and cloud forests

 

"Leaf it" to the sloth

Thousands of years ago, large ground sloths roamed the United States. They ranged in size from an averaged-sized dog to that of an elephant. These ground sloths had long claws and ate plants. They became extinct about 10,000 years ago.

Present-day sloths are much smaller and live in trees. They are related to anteaters. Sloths have large, multi-chambered stomachs (like cows); bacteria in their gut help digest the large amount of plant matter they eat. At the San Diego Zoo, the sloth is fed leaf eater biscuits, yams, dandelion greens, Romaine lettuce, apples, carrots, and some eugenia browse. Grapes are offered as special treats!

I’m a sloth

In a nutshell, sloths are slow-moving, solitary, arboreal, forest-dwelling, nocturnal herbivores. Their sharp claws are 3 to 4 inches (8 to 10 centimeters) long—handy for hanging onto tree branches, but they make walking on the ground quite awkward. However, sloths are great swimmers and will drop from a tree into a river to swim across it while doing the breaststroke! When sleeping, sloths often curl up in a ball in the fork of a tree.

Lean, not mean

With a muscle mass of only 25 percent (most mammals have twice as much), the sloth cannot shiver when it’s cold. But it weighs much less than other animals its size, which is helpful for life in the trees. Sloths can grab leaves and shoots on high, narrow branches that other animals cannot reach. They have two toes with claws on the front feet—as the name implies (three-toed sloths have three claws on the front and back)—and three on the back feet, which are used to hang upside down from branches. In fact, sloths spend so much time upside down that they are the only mammal whose fur is parted running belly to back to allow water to run off quickly during rainstorms!

Slow me the way

Due to the low nutritional value of their leafy diet, sloths are decidedly “lazy” by most mammalian standards, moving quite slowly and sleeping a great deal. Climbing speed is about 6 to 8 feet (1.8 to 2.4 meters) per minute. They sleep 15 to 18 hours per day and (slowly) look for food the rest of the day. Even their innards move slowly, and some food items can take an entire month to digest! This slow metabolism helps sloths survive injuries that would kill other animals.

Watch out!

Big forest cats like jaguars and ocelots, birds of prey such as harpy eagles, and large snakes like anacondas prey upon sloths. They defend themselves with their sharp claws and teeth.

Sloth romance

These ponderous animals spend most of their time alone, but when females are ready to breed, they let out a nighttime “scream” that alerts any interested males. If more than one male reaches her at the same time, the males slowly fight with one another while hanging upside down from a branch by their rear legs! Winner takes all, and several months later, females give birth (still hanging upside down) to a single offspring. The youngster must grab onto its mother's hair at birth and find its way to her breast to nurse. It will stay with its mother for six months to two years, depending on the species, then ‘branch off’ to live on its own.The young inherit a portion of the home range left vacant by the mother, as well as her taste for certain leaves. Several sloths can live in a similar home range without competing for food or space.

Brrrrr!

If our own body temperature changes more than five degrees, it means we are very sick! The two-toed sloth is very different: it has the lowest and most variable body temperature of any mammal, ranging from 74 to 92 degrees Fahrenheit (24 to 33 degrees Celsius), depending on the outside temperature. If, however, there is a long period of cool, rainy weather, females with nursing young can get too chilled and their body temperature drops too low. This causes the bacteria in her stomach to stop working so the mother can no longer properly digest her food. The young will continue to nurse as its mother starves to death. This chilling phenomenon is called cold-weather orphan syndrome, as sometimes the youngster falls to the ground and needs to be rescued by humans if it is to survive.

Conservation status

Though fairly common in their natural habitat, deforestation and other forms of habitat destruction and hunting remain threats for the sloth. Other human-made threats include power lines and roads. Educating children and adults in the sloths’ home countries about the animals' importance to the ecosystem and how to treat the animals respectfully remains a challenge for those who want to help this unique and wonderful animal.