Meet the Southern Maned Sloth: The Latest Sloth Described
Sloths are divided into two large groups: Bradypus, the three-fingered sloths that include the famous smiley and masked-face sloths, and Choloepus, the brownish ones with a pig-like nose and two fingers on each hand. Maned sloths are three-fingered sloths that look like a mixture of Bradypus and Choloepus and are colloquially known as ‘coconut sloths’.
Maned sloths are so different that some scientists consider them to be a different genus, the Scaeopus, although nowadays it is accepted as a subgenus of Bradypus.
One Becomes Two
Although distributed in two distinctive narrow strips of forests on the coasts of Brazil, Maned sloths were thought to be one species. Thanks to Brazilian scientists, a new species, Bradypus crinitus, was added to the list, making a total of seven species of sloths!
Now, the Maned sloths are split into the Northern Maned Sloth (Bradypus torquatus) and Southern Maned Sloth (Bradypus crinitus).
Bradypus crinitus: An Old Name
The research, titled Taxonomic revision of maned sloths, subgenus Bradypus (Scaeopus), Pilosa, Bradypodidae, with revalidation of Bradypus crinitus Gray, 1850, is based on analyses using mitochondrial and nuclear DNA, morphological analyses, and field observations. It was published in the Journal of Mammalogy in September 2022, and as the title indicates, the study revisits and confirms the observations made by British zoologist John Edward Gray.
The (now Northern) maned sloth (Bradypus torquatus) was first described in 1811 by Carolo illigier, and in 1850, Gray claimed to have discovered a second species, which he named Bradypus crinitus. His assertions were later dismissed, with taxonomists agreeing that the specimen described by Gray was in fact B. torquatus. 172 years later, science proved Gray right.
In Latin, crinitus means hairy or long-haired; the Latin word gave rise to “crina” in Portuguese and “crin” in Spanish, which means mane.
Two Populations Separated by a River
The northern maned sloth (Bradypus torquatus) occurs in the Brazilian states of Bahia and Sergipe, and the Southern maned sloth (Bradypus crinitus) occurs in Rio de Janeiro and Espírito Santo states.
The two species’ ranges are separated by the Rio Doce, which also acts as a dividing line between other related species, like capuchin monkeys (Cebus nigritus and C. robustus). However, the researchers are unable to say whether the river provides a physical barrier or if contrasting climatic and geographical features on either side of this marker are responsible for these phylogeographic breaks.
“This separation was probably further aggravated by anthropogenic habitat fragmentation and deforestation in the Atlantic Forest. These processes potentially restricted the gene flow among the populations,” write the authors.
Phylogenetics and Physical Differences
The southern maned sloth separated from its northern counterparts in the Early Pliocene around 4 million years ago. There are no clear physical differences between B. crinitus and B. torquatus that you could notice using only your eyes.
The researchers examined 55 samples of skull, bones, and skin. The samples came from different museums and institutions in Brazil, as well as from collections from other countries, such as the Natural History Museum of London.
After meticulous measurements, researchers concluded that compared to northern maned sloths, southern sloths have flatter skulls, rounder jaws, and wider cheekbones. B. crinitus is often more gray than B. torquatus.
Are Two Maned Sloths Better Than One?
It’s always a celebration when a new species is listed, and it’s always wonderful when science surprises us. But a discovery like this also comes with the realization that maned sloth populations are much smaller than we initially thought. And this is a big issue since maned sloths as a group were already considered Vulnerable by the IUCN with declining populations.
At the moment, there is not enough data or information to assess the conservation status of the newly described Bradypus crinitus, but it is likely to be vulnerable or critically endangered.
“With the new taxonomic arrangement proposed here, the geographic distribution of each species becomes relatively smaller, with each one of the two species suffering under different anthropic pressures” explain the authors of the research. Despite this, the good news is that scientific knowledge about the new species will give conservationists better tools to protect the species. Now that we know that both species have smaller home ranges, organizations and authorities must take deep and improved actions to preserve the maned sloth species.
-Cecilia Pamich
Communications & Outreach
