Science & Technology

The mammals evolved from the ground to the trees.

Sloths are dog-sized animals that live in the tropical rainforests of Central and South America. They are known for moving very slowly – this is due to their extremely low metabolic rate. Because sloths do not move well on the ground, they spend much of their time high in the trees, safe from predators. Sloths’ long arms provide great swimming abilities, which aid in their survival.

The History

Sloths are most closely related to armadillos and anteaters, which have been around since the Paleocene epoch, around 60 million years ago. The suborder, xenarthrans, which includes all three animals, is a group of creatures known for slow metabolisms and lack of teeth. Though closely related, there are both two-toed and three-toed sloths. Recent scientific discoveries have revealed that today’s two-toed sloths are related to the giant Mylodon that went extinct in South America less than 10,000 years ago, and three-toed sloths are related to the horse-sized ground sloth Megalonyx and the elephant-sized Megatherium (both extinct for more than 15,000 years).

What helped prevent the sloths from extinction was their evolution to become tree-dwelling animals. Both two-toed and three-toed sloths evolved in the same way, though separately, a phenomenon called convergent evolution.

Hairy and Solitary – Appearance and Behavior of Sloths

Sloths are hairy with fur that can be brown, gray, white, or tan. The animal is between 24 and 31 inches long and weighs 7 and 17 pounds. There are a couple of differences between the two-toed and three-toed versions. For instance, two-toed sloths have two toes on each front foot, but three on the back, while three-toed sloths have three toes on each foot. Additionally, two-toed sloths have five to seven neck vertebrae, and three-toed sloths have seven to nine vertebrae. This unique feature allows the animal to turn its head more than a human can. They are equipped with long arms and long, sharp claws that not only allow them to be great swimmers but also great hangers. They spend much of their time hanging upside down from tree limbs.

Sloths’ fur is unique, which, unlike that of other mammals, grows away from their arms and legs and parts down the middle of their chests and bellies. Their fur is hollow, permitting algae to grow inside it, creating natural camouflage. Also interesting is the ecosystem that exists within the fur. Insects such as mosquitoes, sandflies, mites, ticks, beetles, and moths live within the hollow of their fur.

Sloths have weak eyesight and hearing, relying significantly on their strong sense of smell and touch to safely navigate habitats. They maintain a low body temperature, between 86 and 93 degrees Fahrenheit when active, and even lower temperatures when resting. Sloths sleep for nearly 20 hours per day! This leaves little time to hunt, eat, and play. They only leave the comfort of the trees once per week to use the restroom and then get back to safety.

They are overall solitary creatures. Nearly the only time spent with other sloths is when looking for a mate or raising their children (the females tend to congregate more than males).

What’s for Dinner?

Three-toed sloths are herbivores, meaning they eat only plants and fruits. Two-toed sloths, however, are omnivores and will eat both plants and small animals and insects. Both species carry on the theme of slow even when it comes to their food digestion rate. It takes them one week to one month to digest a single meal!

Are Sloths on the Menu?

Hanging out high in the trees makes sloths slightly less fearful of predatory attacks. However, they are not completely out of the woods. Large cats like jaguars, as well as snakes and large birds of prey, are threats. Still, the slow-moving mammal has one last trick up its sleeve. One thing they love to eat is poison ivy, which does not affect them like it does most other mammals. If an animal eats a sloth that has munched on the poisonous plant, the toxins attack them from the inside out, causing swelling, irritation, and ultimately death by suffocation.

Other Valuable Information

It is difficult for humans to tell the difference between a female and a male sloth. Often, the wrong gender is sent to zoos, making reproduction in captivity difficult. Also, mother sloths will sometimes drop their babies from their homes high up in the trees and are too lazy to retrieve them, causing the young animals to die. Finally, scientists do not know how long a sloth can live in the wild. The oldest captive sloth lived 49 years, but the average lifespan for the mammal is somewhere around 16 years.

1. Sloths are dog-sized animals that live in the tropical rainforests of Central and South America and are known for moving very slowly.
2. What helped prevent the sloths from extinction was their evolution to become tree-dwelling animals.
3. Sloths sleep nearly 20 hours per day, leaving little time to hunt, eat, and play.