Sloths are one of the most endearing animals on Earth, recognised by millions through nature documentaries, film and even memes. But how much do we know about them? Here’s a look into the life and origins of sloths.
There are two variants of sloth that make up the six species; two-toed and three-toed. These species consist of Linnaeus’s two-toed; Hoffman’s two-toed; Pale-throated; Brown-throated; Maned; and Pygmy. Out of the six the Pygmy and Maned are the most threatened, being classified by the IUCN as Critically Endangered and Vulnerable respectively.
All sloths are found in the rainforests and cloudforests of Central and South America and no species grows larger than a medium-sized dog, however this wasn’t always the case. Megatheriidae was a family of giant ground-sloths existing through the Early Pliocene to the Early Holocene. The genera Megatherium, native to South America, and Eremotherium, its North American cousin, were both around 20ft long and the size of modern elephants.
Sloths gained their name when naturalists observed their slow-moving nature and attributed it to the sin of laziness, however their slowness is actually an evolutionary strategy to conserve what little energy they get from the vegetation they eat. The metabolic rate of sloths is so low it can take up to a month to digest a single meal. The leaves, shoots and buds that make up their diet are nutritionally poor, meaning they only move approx. 40m a day. Another advantage of this lethargic locomotion is it facilitates the growth of algae on their fur, camouflaging them against the green of the jungle and hiding them from predators.
They do almost everything in the canopy, from eating to sleeping and mating; even giving birth in the treetops. There are two exceptions to this however. A sloth will venture to the forest floor to either swim (as seen on Planet Earth II) or to defecate.
Sloths only answer the call of nature once a week and this odd bathroom habit has led to a remarkable symbiotic relationship. The algae that grows on sloth fur provides a vital food source for certain species of moth. As a sloth descends to do its business so too do the moths. Once down there the moths lay their eggs in the fresh dung just in time to hop back onto the sloth to continue feeding. Obviously laying your eggs in fresh faeces is a dirty job so the now dung-covered moths traipse back the perfect fertiliser for the algae. The algae is fertilised further when adults emerge from the dung and find other sloth-moths to mate with.
Before this mutualism was discovered it was rather baffling that sloths would undergo such a risk of predation just to go to the bathroom, but theories have emerged that suggest instead of the moths simply taking advantage of sloth habits, the relationship between moths, sloths and algae has deep-seeded evolutionary origins. That the algae fertilised by the moths also fills a crucial nutrient gap in the sloths’ diet, making the dangerous trip a trade-off, worth the risk to preserve such a relationship.
Though four of the six species are not as troubled as the Pygmy and Maned, the preferred habitat of all sloths is one of the most vulnerable in the world. Habitat protection from deforestation and more conservation data is essential to their future. If you would like to get involved in sloth conservation check out our projects in Costa Rica.
By Thomas Phillips - Online Journalism Intern