The Pygmy Sloths of Panama

The Pygmy sloths of Panama are considered to be one of the world’s most critically endangered mammals with the last official population count identifying only 79 individuals. Beyond the original description of the species we still know almost nothing about these little sloths with scientific rigour. We don’t know how many of them remain, we don’t know enough about their diet and habitat needs, we don’t understand when and how they reproduce, and we still don’t really know why and how they became dwarfed on their small island.

What Are Pygmy Sloths?

Pygmy sloths are a dwarfed version of the brown-throated three-fingered sloths found on mainland Panama, but this species is endemic to the remote Isla Escudo de Veraguas. This tiny island, which only formed 9000 years ago, is located 17.6 km off the coast of mainland Panama and covers just 4.3 km2. The pygmy sloths were first described as a distinct species in 2001 based on morphological differences in body size (they are reportedly 40% smaller than the mainland species), but due to a lack of research we still have no genetic information on the status of these animals. Isla Escudo is very difficult to get to, and much of the mixed forest coving the interior of the island remains unexplored. The Pygmy sloths are most commonly found inhabiting and feeding from red mangrove thickets, but these trees are often logged and now only constitute 0.024% of the total island area (1.67 ha). No one really knows whether these little sloths use the dense mixed forest covering the interior of the island, or whether they feed from anything other than red mangrove leaves. With the number of remaining pygmy sloths suspected to be in decline, it is becoming essential that we work towards better understanding the ecology of this amazing species.

In addition to the Pygmy sloths, there are also known to be four other nearby islands in the Bocas del Toro archipelago that support three-fingered sloths smaller in size due to their confinement on an island. Despite being a similar size to the pygmy sloths, these island sloths are still classified as Bradypus variegatus (the mainland species), but the genetic status, health and ecology of these isolated populations are poorly understood.