Sloths
Sloths—more specifically three-toed sloths, the most common type—are one of the slowest moving, most easy-going animals around. They live almost entirely high up in the trees; they are strictly vegetarian, eating mainly leaves (which they digest over 30-50 days); and they sleep 15-plus hours a day. As one writer put it, sloths are “masters of an alternative lifestyle.”
Three-toed sloths are found in Central and South America. They grow to 15-20 pounds and can live 30 years or more. They hang upside down to sleep, and are largely solitary rather than living in groups. They are not considered an endangered species.
Which raises the basic question of why they are still around. How could sloths not only survive in the wild with numerous potential predators—much larger, faster, and stronger—but how could they have survived for 50-60 million years? They aren’t big enough to scare off predators (the sloth that was large—the giant sloth—died off long ago), and when on the ground (which they go to once a week to relieve themselves) there is basically no animal they can outrun—moving at the pace of a giant tortoise (their “top speed” is listed at 15 feet/minute).
The answer is that sloths are in fact remarkably well adapted to survive. Not only because they spend almost all their time high up in trees, out of the reach of predators, but also because they are very difficult to spot: most of the time they are not moving, plus their sedentary life allows green algae to grow on their fur, giving them excellent camouflage. Their unusual ability to rotate their heads 270 degrees each way allows them to scan for danger without moving their bodies. The shape of their claws and limbs creates a natural gripping reflex so all their time spent hanging upside down requires no effort. And in the rare moments when they are on the ground, they are not defenseless: those large, sharp claws also give them very sharp weapons to ward off an attacking animal like a jaguar. Indeed, the effectiveness of their adaptation is reinforced by the fact that the three-toed sloth and two-toed sloth are distinct species that evolved separately but in parallel ways over many millions of years into their current unusual lifestyle. It’s been called “one of the most striking examples of convergent evolution known among mammals.” The peaceful, low-key approach worked.
Indeed, they are so well adapted to their environment that their only major threat comes from humans—as we destroy their rainforest habitat for timber or cattle grazing. Yet all is not lost. In recent years there has been a remarkable growth of interest in sloths and their continued existence. Receiving almost no attention for thousands of years other than negative comments about their “laziness” or being associated with the Seven Deadly Sins, they are now getting serious attention from field researchers, scholarly articles, popular books, wildlife protection groups—even a host of recent children’s books and being featured in the movies: sloths had charming roles in the Disney animated movie “Zootopia”—as clerks in the department of motor vehicles, of course! And governments and international organizations are weighing in. Costa Rica, for example, featured sloths on a postage stamp and made them national symbols of their wildlife. All of which helps to brighten the outlook for these peaceful and shy creatures.
