Sloths

Centuries ago, North America was home to large ground sloths. They varied in size, some as small as dogs and others as big as elephants, feasting primarily on plants. But around 10,000 years ago, they vanished.

Today, sloths reside in the tropical forests of Central and South America. While their long arms and furry bodies might remind one of monkeys, they are in fact closer relatives of armadillos and anteaters.

Sloths move at a snail’s pace, and their diet is a major reason. They feast on a mix of leaves, stems, buds, and occasional fruits. To handle this fibrous menu, they come equipped with a large, multi-chambered stomach designed for tough leaf digestion.

They nap for up to 18 hours daily and (slowly) search for food at night. Since their metabolism runs on the slower side, they can only eat more leaves when there’s space in their often-packed stomach, which can take up a whopping 37% of their body weight. Digestion isn’t quick either; some meals can take up to a month to process.

Sloths are nature’s energy conservers. Their curved claws enable them to hang effortlessly, requiring only half the muscle mass typical mammals need. Also, unlike humans, sloths have an extremely fluctuating body temperature, from 74°F to 92°F (24°C to 33°C). They’ve traded body temperature regulation for energy conservation. Sunbathing helps them warm up, but if they cool down too much, the essential microbes in their stomach can die, impeding their ability to digest leaves.

Amazingly, sloths do most activities upside down―including eating, sleeping, mating, and even childbirth. This lifestyle has their fur growing in a unique way, moving away from their limbs and splitting at the belly. Their fur is also a haven for algae, providing them with a greenish tint that acts as camouflage.

This slow-moving approach and camouflaging fur might be evolutionary tactics to evade sharp-eyed predators like hawks and cats. If threatened, though, sloths defend fiercely, using their long claws and strong bites.

On land, their long claws make movement cumbersome. About once a week, they come down to relieve themselves, dragging themselves forward using their front claws. Yet, they’re surprisingly good swimmers, often diving from trees to swim across rivers.

Two sloth families exist, distinguishable by the number of claws on their front feet: two or three. The two-toed Choloepus sloths are slightly larger and prefer hanging upside-down. In contrast, three-toed Bradypus sloths often sit upright on tree branches. A unique trait of the three-toed species is their seemingly ever-present smile and an ability to almost rotate their heads 360°, thanks to two additional neck vertebrae.

In their natural habitat, sloths have a lifespan ranging from 20 to 30 years. They are typically solitary creatures. Yet, when the mating season arrives, a female’s loud nighttime call can draw multiple males. If that happens, the males, ever so slowly, duke it out while suspended by their back legs. After mating, sloths usually have a single offspring. The baby feeds on their mother’s milk for several months and remains by her side for roughly a year.

Lastly, while not all sloth species are at risk, some face threats from deforestation in Central and South America, endangering their crucial food and shelter sources.