May 24

The first ever formal survey of the pygmy three-toed sloth population has confirmed that it is one of the world’s most endangered mammals.

Pygmy three-toed sloth image

The pygmy three-toed sloth is classified as Critically Endangered on the IUCN Red List

Hanging on

A strange-looking yet charismatic mammal, the pygmy three-toed sloth is only found on Escudo Island off the coast of Panama, and was discovered by scientists as recently as 2001. As well as being the world’s slowest sloth, this species is also the world’s smallest, being just 40% of the size of its mainland relatives.

Very little is known about the pygmy three-toed sloth, but the latest data collected by researchers from the Zoological Society of London (ZSL) has provided the first accurate picture of the state of the species’ population. Previous population estimates ranged from 300 to 500 individuals, but the new research has revealed that these numbers were sadly rather optimistic.

Due to the species’ small population size and its evolutionary uniqueness, ZSL’s EDGE of Existence programme has placed the pygmy three-toed sloth at number 16 on its list of the world’s 100 most unique and threatened mammals.

Pygmy three-toed sloth image

Male pygmy three-toed sloth swimming

Mangrove home

The pygmy three-toed sloth relies on the island’s mangrove forests for survival, as ZSL researcher Craig Turner explains: “The mangrove forests are relatively hard to penetrate, and from a sloth’s perspective they provide protection from aerial predators. We noticed that pygmy sloth mothers carrying young would remain low in trees, which may be an evolutionary hangover for predator evasion.

Depending on the temperature, sloths can be found at different heights in the mangrove forests, moving higher up the trees on cool days to catch the sun and remaining lower down to rest in the shade when temperatures are high.

Conservation plans

Following on from the valuable information obtained from the ZSL team’s research, the next step is to draft a conservation plan for the pygmy three-toed sloth to ensure its future survival. Currently, the precise reasons for its decline are unknown, but tourism, hunting, and the deforestation of mangroves, either alone or in combination, are all possible causes.

In 2009, all of Escudo Island was deemed a protected area. However, concerns for the pygmy three-toed sloth remain, as the island is a common stopover point for local fishermen and their families who sometimes bring dogs with them. Exploration of the island by Craig Turner and fellow researcher David Curnick also revealed a certain level of mangrove deforestation, presumably for charcoal production by local fishermen.

[Reforestation] is an option we hope to explore with the view to potentially develop a local community reforestation pilot project. However, there are areas of cleared mangroves already showing small signs of regeneration so it may be a case of buying them some time to establish themselves,” said Mr Curnick.

Pygmy three-toed sloth image

This sloth species relies on the presence of mangrove forests

Saving the sloths

Mr Curnick and his colleagues are aiming to further evaluate the risks to the pygmy three-toed sloth by undertaking a complete threat assessment. At present, the research team believes that the formation of a coalition devoted to the long-term survival of the species is one of the key components in saving it from extinction.

I would like to see better engagement with the local communities and stakeholders and the development of a local environmental management plan. This is a process we have already started and hope to develop this aspect of the project over the remainder of this year. We are also seeking funding to support a local Panamanian conservationist to take this, and other areas forward, through the EDGE Fellowship programme,” explained Mr Curnick.

A ‘last resort’ option would be to remove a few sloths from the island for a captive breeding programme, but with so little known about the ecology and biology of the species, Mr Curnick warns that this would be a difficult and risky strategy. “As a family, three-toed sloths are notoriously hard to keep in captivity, let alone breed, and I imagine the pygmy sloths will only be more difficult,” he said.

Along with ensuring the survival of the pygmy three-toed sloth, the ZSL research team hopes to be able to conduct a wider ecological assessment of Escudo Island, as it is home to two other Critically Endangered species which are found nowhere else on Earth: the neotropical fruit bat and the maritime worm salamander.

Read more on this story at – Less than 100 pygmy sloths survive.

Learn more about the pygmy three-toed sloth on ARKive.

Find out more about the EDGE of Existence Programme.

Kathryn Pintus, ARKive Species Text Author

  • Jakob Shockey (June 1st, 2012 at 7:42 pm):

    There was also a population census completed in the spring of 2011. It was conducted independently, by three students from Evergreen State College. Their results are currently being reviewed with a scientific journal.

    Here’s a link to a story published on that trip:

    Or google “Of Sloths and Men”