Sloths are slow-moving mammals native exclusively to the tropical rainforests of Central and South America. Their unique biology is defined by an extremely low metabolic rate, which dictates their slow pace of life and their almost entirely arboreal existence high in the forest canopy. They possess specialized long claws that allow them to spend most of their lives hanging upside down, even eating, sleeping, and giving birth in this suspended position. These iconic creatures face various modern threats that challenge their survival in the wild.
The Six Distinct Species
Answering the question of how many sloths are left requires recognizing that there is no single global count, as the six recognized species are tracked individually. These six species are divided into two taxonomically distinct families, an evolutionary split that occurred roughly 40 million years ago.
Two-Toed Sloths
The two-toed sloths belong to the family Megalonychidae and include Hoffmann’s two-toed sloth and Linnaeus’s two-toed sloth.
Three-Toed Sloths
The three-toed sloths are classified under the family Bradypodidae and are generally smaller than their two-toed cousins. This group consists of four species: the Pale-throated three-toed sloth, the Brown-throated three-toed sloth, the Maned three-toed sloth, and the Pygmy three-toed sloth. Despite their common names, all sloths possess three claws on their hind limbs; the difference lies only in the number of claws on their forelimbs.
Current Global Conservation Status
The population outlook for sloths varies dramatically across the species. Four of the six are currently classified by the IUCN Red List as Least Concern. This classification applies to the two two-toed species (Linnaeus’s and Hoffmann’s) and the two most widespread three-toed species (the Brown-throated and Pale-throated sloths). While these species are relatively numerous and widespread, exact total population numbers are impossible to calculate due to their elusive nature in the dense forest canopy. Density estimates suggest that where suitable habitat remains, these species can maintain large, stable populations.
In contrast, the outlook for the two remaining species is more precarious due to their limited geographic ranges. The Maned three-toed sloth, endemic to Brazil’s highly fragmented Atlantic Forest, is classified as Vulnerable. Habitat loss has reduced its range significantly.
The Pygmy three-toed sloth is listed as Critically Endangered. This sloth is found exclusively on the tiny Panamanian island of Isla Escudo de Veraguas, making its population highly susceptible to local environmental changes. Population estimates range between 500 and 1,500 individuals. Even at the highest estimate, this population is extremely small for an entire species and remains at risk of extinction.
Primary Factors Driving Population Decline
The foremost threat to sloth populations across all species is the rapid rate of habitat loss and fragmentation resulting from agricultural expansion and urban development. Sloths rely completely on a continuous forest canopy for safe movement. When large tracts of forest are cleared, the remaining patches become isolated islands. This fragmentation forces sloths to descend to the ground, where they are exposed to predators, dog attacks, and vehicular traffic, hazards they are biologically unprepared to face.
Electrocution is a major cause of injury and fatality, often being the second most common reason sloths are admitted to rescue centers. In urbanizing areas, sloths mistake uninsulated power lines for tree branches, which can lead to severe internal and external burns when they come into contact with the high-voltage wires. This is a direct consequence of habitat loss pushing wildlife into increasingly human-dominated landscapes.
The illegal pet trade also contributes to population decline, particularly for baby sloths sought by tourists and traffickers. These young animals are often violently separated from their mothers and suffer high mortality rates, with estimates suggesting 80% to 90% of trafficked sloths die during the process. Sloths sold as pets often have their claws clipped, making them unable to survive if later released back into their arboreal homes.
Climate change poses a serious threat, particularly to geographically restricted and high-altitude populations. Sloths have a slow metabolism and limited ability to regulate their body temperature, making them vulnerable to rising heat. Studies indicate that sloths cannot increase their food intake to compensate for the higher metabolic demands of warmer temperatures, threatening their long-term survival.
Global Conservation Initiatives
Conservation efforts are largely focused on mitigating the dangers posed by habitat fragmentation and human infrastructure.
Wildlife Corridors
One prominent initiative involves the installation of artificial wildlife corridors, such as rope bridges known as “Sloth Speedways,” to physically reconnect isolated patches of forest canopy. These structures allow sloths and other arboreal animals to safely bypass dangerous roads and power lines, with some projects successfully installing hundreds of these bridges across fragmented landscapes.
Reforestation and Monitoring
Reforestation projects are also underway, often working directly with local landowners to restore ecological balance in urbanized areas. Organizations establish tree nurseries to grow thousands of native saplings, selecting a mix of fast-growing species for immediate canopy cover and slower-growing, long-term food trees to ensure sustainable habitat restoration. To inform these strategies, conservationists are employing advanced research methods, including thermal drone technology and specialized scat-detection dogs, to accurately locate and monitor sloths in the dense canopy. This scientific monitoring is essential for determining which areas require the most urgent intervention.
Educational Outreach
Educational outreach programs are a central component of global initiatives, especially in communities near sloth habitats. These programs, delivered in multiple languages, focus on teaching local children and adults about sloth biology, the risks of the illegal pet trade, and how to report injured animals. By promoting a sense of stewardship, these efforts aim to change behaviors.