Sloths are some of the slowest animals in the world — here's why

Sloths are notoriously slow. Living in rainforests in Central and South America, sloths spend most of their time hanging upside down in the trees, rarely coming down to the ground.

There are two main families of sloths, two-toed sloths, and three-toed sloths, and they all share something in common: They've been around for millions of years – 64 million, to be exact.

For comparison, modern humans have only been around for about 200,000 years.

Sloths slowness, as it turns out, is the key to their survival. Far from being lazy, sloths are actually really efficient at conserving energy, and it all has to do with their diet.

There are four main types of three-toed sloths (pictured below) living everywhere from Mexico to coastal Brazil. They're some of the slowest mammals in the world

Spending most of their lives hanging upside in trees, sloths move no further than 125 feet per day. When they make it to the ground, they crawl at a pace of about 1 foot per minute, according to the World Wildlife Federation.

Sloths are slow because of their diet. They mostly eat leaves, twigs, and flowers they can easily reach from where they are hanging.

Their herbivorous diet is low in energy and lacks much of the nutrients needed — like fats and protein — for a balanced meal.

But sloths have a secret up their sleeve: Their slow metabolic rate means they can survive off of very little food, which is especially useful during droughts.

They also take days to digest a meal, meaning they only leave their perches to defecate around once a week, reports Scientific American.

Rarely leaving the trees means sloths are protected from predators, like jaguars and eagles, which can pick younger or weaker sloths off of the forest floor.

Because sloths rarely move, they grow algae on their fur, helping them camouflage with their arboreal home. It's a neat trick for avoiding sharp-eyed eagles.

Beyond algae, sloth fur is also a habitat for a whole range of organisms, from moths and cockroaches to fungi.

Sloths are extremely sleepy, snoozing for over 15 hours a day.

While they mostly slumber on comfortable branches, here, this man's hand seems like a suitable substitute.

Sloths do most of their moving, and feeding, at night, snoozing away the hot temperatures of the day.

Sloths are well adapted to their rainforest habitat. But, like many forest-dwelling critters, they are threatened by habitat destruction and deforestation.

Deforestation throughout Central and South America is putting pressure on sloths. The pygmy sloth, the smallest of the sloths that only lives on an island of the Caribbean coast of Panama, is critically endangered.

Sloth moms only give birth about once every six months. The babies cling to their mom for around six months, learning the ropes of what it takes to survive in the jungle

When sloths leave the safety of their mother, they adopt part of their parent's home range, staying in touch through frequent calls, according to the WWF.

While sloths have strong bonds with their mothers, their low birth rate hurts their ability to recover from habitat destruction.

They are pretty unique creatures.

A sloth made his star turn in Planet Earth II, searching for love on the beautiful island of Escudo off the coast of Panama.