Sloths belong to the ancient mammalian order Xenarthra, along with armadillos and the South American anteaters. Within this order, sloths are thought to be more closely related to anteaters than either group is to the armadillos. Recent molecular studies indicate that sloths and anteaters diverged around 37 million years ago. Sloths are the most diverse group of xenarthrans, with up to 100 known fossil genera, one of which was even aquatic (the Pliocene Peruvian genus Thalassocnus). Ground sloths were very diverse in the Americas during the Pleistocene, but all of these became extinct around 10,000 years during a major extinction of megafaunal mammal species following prehistoric human arrival in the Americas. Only five species of arboreal sloth survive today, in two families: Bradypodidae (three-toed sloths) and Megalonychidae (two-toed sloths). These families are thought to have diverged around 18 million years ago. There are four species of three-toed sloth, in the single genus Bradypus: B. torquatus (maned three-toed sloth) B. variegatus (brown-throated three-toed sloth) B.pygmaeus (pygmy three-toed sloth) and B. tridactylus (pale-throated three-toed sloth). B. torquatus is estimated to have split from the other two species about 7.7 million years ago.
The largest of the four species of sloth, the maned three-toed sloth is named after its long mane of black hair, which runs down the back of the neck and over the shoulders. The rest of the coat is a greyish-brown colour, although it frequently has a greenish tinge because of the algae that live in the hair. This algal growth provides the species with excellent camouflage, enabling it to blend in perfectly with the trees in which it lives. The fur is long and coarse, and grows in the opposite direction to that of most mammals, so that the hairs point downwards when the animal is hanging upside-down from a branch. The head is small and round, with a flat face and small ears hidden in the fur. Sloths have short bodies, long limbs and stumpy tails. Three-toed sloths are so-called because they have three digits on each limb (two-toed sloths have three digits on their hind limbs, but only two on their forelimbs). Each digit ends in a long curved claw, which the sloth uses to hook around branches. Whereas most mammals have seven neck vertebrae, three-toed sloths have eight or nine. This allows greater flexibility in the head movements, enabling the animals to turn the neck through an arc of 270 degrees.
Classified as Vulnerable B2ab(i,ii,iii) on the 2011 IUCN Red List of Threatened Species.
The maned sloth is one of the most threatened of the South American sloth species, owing to its restricted geographical range and the disturbed and fragmented nature of its forest habitat. The Atlantic coastal rainforest of Brazil is diminishing rapidly as a result of logging, charcoal production, and clearance for plantations and cattle pasture. Today, the Atlantic forest is reduced to less than ten percent of its original area, and the Mata Atlântica region in which the species lives has the highest human population in Brazil. Maned sloths have a highly fragmented distribution, with large gaps between the major populations. This means that many existing populations may be too small to be viable. The species has traditionally been hunted for its meat, and this may continue to threaten its survival in some areas, despite now being protected by law.
Although maned sloths occur in at least eight protected areas, it is unlikely that any of these support viable populations, because of the highly fragmented distribution of this species. Extensive conservation efforts are currently underway to protect additional areas of the Atlantic coastal rainforest, since it is home to a great number of species found nowhere else on the planet. The WWF is currently involved in community projects which seek to educate local people about the importance of protecting this forest. The US Agency for International Development (USAID) is working on reduced-impact forest management and on providing alternatives to slash-and-burn agroforestry. Conservation International (CI) is focussing on ecotourism as a possible alternative income for local communities which might otherwise have cleared areas of forest for agriculture. In 1998 a canopy walkway was built near the Una Biological Reserve, saving 320 acres of valuable rain forest habitat from logging. Efforts to translocate individuals from urban or agricultural areas to protected forest reserves appear to have been relatively successful so far. Extensive post-translocation monitoring has been carried out, which is providing important data about the species’ ecology and habitat requirements, as well as an indication of the success of the translocations themselves. Attempts to breed the species in captivity have not proved as successful. This is primarily due to the fact that these sloths do not survive for more than a few months outside of their natural environment. Research projects are focusing on the close relationship between females and offspring, so that breeding and re-introduction programmes in the future are better informed and more successful.
As of 2010 this species has been included in the Brazilian government's ‘National Action Plan (NAP) for the conservation of central Atlantic forest mammals'. Costing an estimated US$32 million, this scheme aims to conserve geographic regions over specific species. Nonetheless, 27 named species, including the maned three-toed sloth are specifically targeted in the plan. The early stages of this NAP focused on compiling all known biological and threat data relative to these target species. With this information, 60 individuals, representing a range of national and international bodies, were able to construct 6 main goals and 100 specific actions to guide future conservation efforts. Compiled in 2010, the goals of this project include: maintaining, enlarging and connecting protected habitats, managing sloth populations (genetically and demograpically) to ensure their viability, reducing hunting pressures, ensuring scientific knowledge on taxa and threats remains up to date and pressuring for guidelines documented in this project to be reflected in national policy.
Adriano is a sloth expert working to conserve sloths in Brazil
Adriano is an expert on maned three-toed sloths
Rebeca works on the conservation of maned sloths in Brazil
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