It was just twelve years ago that scientists first observed and described a new mammalian species living on a tiny remote island, 17 kilometers (10.5 miles) off of the coast of Panama. And, like the small island that it inhabited, this mammal was also small. It was a miniature version of its nearest mainland relative. The newly “discovered” species was a type of three-toed sloth which was aptly named, Bradypus pygmaeus, Pygmy Three-Toed Sloth. This unique creature is considered to be the world’s smallest, slowest, and most docile sloth.
The island of Escudo de Veraguas, about 430 hectares (1063 acres) in size, is the only place on earth that the pygmy three-toed sloth exists. Further, it is found solely in the red mangrove forests surrounding the island, currently estimated to be 150 hectares (371 acres) in area. As far as it is known, the pygmy sloth exclusively feeds on the mangrove leaves.
Where did the Pygmy Three-Toed Sloth Come From?
About 9000 years ago, the sea level began to rise, isolating small tracts of land from the mainland. A population of brown-throated three-toed sloths became marooned. Over thousands of years, evolution and natural selection worked to reduce the size of the island sloths, a process known as insular dwarfism.
In addition, the sloths acquired other traits and characteristics that allowed them to become very well adapted for life on the island. Eventually a genetically distinct species evolved, the pygmy three-toed sloth.
Natural History and Behavior
Sloths belong to the same taxonomic order as armadillos and anteaters. Central and South America are home to two genera of sloths: the two-toed and the three-toed sloths. They are so called because of the number of claws found on the forefoot. (Both have three claws on their hind feet.) On the mainland, both types occupy the same forests. However, the two-toed sloths are omnivores, eating a variety of leaves and fruits, as well as bird eggs and slow moving creatures. They also tend to be larger. The three-toed sloths, like the pygmy sloth, are herbivores that browse on leaves. They are the smaller genus, and in the case of the pygmy sloth, is less than half the size of its mainland counterpart. The pygmy three-toed sloths also tend to be more lethargic. This has to do with the low energy content and possible toxins found in the leaves they eat.
“Hanging around” is something all sloths do. They are so well adapted to living in trees, partially because of their long curved claws which allow them to hook over tree branches, and partially because of the design of their body, whereby all four limbs act more like arms than legs. Additionally, their limbs are built to withstand long periods of hanging upside down.
This uses far less energy than what most animals use standing up. Given their specialized arboreal design, they are relatively helpless on the ground, barely able to support their own weight. However, the pygmy three-toed sloth is an excellent swimmer and frequently uses this mode of transportation to get from one mangrove patch to the other. Aided by its big stomach and low body mass, it actually floats like a ballon and then uses its legs to do the doggy paddle for propelling.
Sometimes sloths may be caught napping as they dangle upside down, but more often curl up into a little furry ball in the fork of tree limbs. Sleep is a major part of their life. Eighteen to twenty hours of sleep a day is not unusual. Whereas the mainland sloths typically sleep through the night, the pygmy sloth is more active during the night. This may have to do with the absence of natural predators, like jaguars, that generally hunt in the dark.
It is because of their long periods of sleep, combined with minimal grooming and docile behavior, that invites any animal that wants to do so, to live within its coat of coarse shaggy fur. And many organisms do. Algae grows on its long outer hairs, giving the sloth a green hue during the rainy season and a dirty brown cast during the dry season.
In both cases, the change in color helps camouflage sloths against the rainforest backdrop. The pygmy three-toed sloth has a unique species of algae growing on its hair. It is thought to be transferred from mother to child. In addition to the algae, several specialized moths and beetles live in the sloths fur. It is not clear what benefits, if any, the sloths gain, but the benefits are many for the “free loaders”, including transportation, protection and a place to mate!
Sloth Sanctuary Costa Rica
Pygmy Three-Toed Sloth Threats and Conservation Efforts
Today, the population of the pygmy three-toed sloths stands at less than one hundred animals. They are critically endangered and have been classified as such on the IUCN Red List of Threatened Species. Although some indigenous peoples hunt the pygmy three-toed sloths for medicinal purposes, the sloth’s greatest danger is not from being hunted, but from destruction of their vital and very limited mangrove habitat.
The island of Escudo de Veraguas is designated a marine nature reserve, where humans are not allowed to live on the island, nor are they allowed to interfere with any of its plants and animals.
Unfortunately, the rules are not strictly enforced. Visiting fisherman and nearby indigenous peoples come to the island, clearing the mangrove forests for wood and building material, further depleting the the pygmy sloth’s habitat. If an effort is not made to increase local awareness of the sloth’s plight and if law enforcement is not improved for this protected area, then there is a good chance the pygmy sloth may disappear within the next ten years, only twenty-two years from its initial discovery.
It would be a big shame and a very poor reflection on man, if he did not allow this unique and fascinating creature to “hang around” much longer.