Imma Perfetto
Cosmos science journalist
A new study warns that sloths living in high-altitude rainforests of South and Central America could face extinction if temperatures there continue to rise according to climatic predictions.
The research, published in PeerJ Life & Environment, suggests that some sloths’ restricted ability to migrate to cooler regions and limited metabolic flexibility make them particularly vulnerable to climate change.
“Sloths are inherently limited by their slow metabolism and unique inability to regulate body temperature effectively, unlike most mammals,” says Dr Rebecca Cliffe, lead researcher of the study from Swansea University and The Sloth Conservation Foundation in the UK.
“Our research shows that sloths, particularly in high-altitude regions, may not be able to survive the significant increases in temperature forecast for 2100.”
At the Sloth Sanctuary of Costa Rica, the researchers studied 12 adult 2-fingered sloths (Choloepus hoffmanni), which had originated from either highland or lowland rainforests in the wild.
By measuring the sloths’ core body temperatures and oxygen consumption, the researchers showed that highland and lowland sloths respond differently to ambient temperatures ranging from 18 to 34 °C.
As temperatures rose above 32 °C, lowland sloths, which are better adapted to higher temperatures, depressed their metabolic activity as a survival mechanism.
The sloths from highland regions lacked this capability and experienced a sharp increase in their resting metabolic rate instead.
Because sloths have such a slow digestive rate, up to 24 times slower than other similar-sized herbivores, this increased energy expenditure can’t easily be balanced by increasing energy (food) intake.
The researchers used this data to predict the metabolic and body temperature impacts of future climate change projections in the different sloth populations.
“While future climatic predictions for the South and Central American rainforests are variable, all point towards these regions becoming hotter and drier, with current estimates forecasting a 2–6 °C increase in average daily air temperatures by the year 2100,” the authors write in their paper.
They predict that while lowland sloths may cope with warmer temperatures by shifting their ranges to higher altitudes, high altitude sloths’ limited metabolic and limited geographical flexibility may limit their ability to adapt to a continuously warming climate.
“We predict that a comparatively small increase in ambient temperature could see high-altitude sloths pushed into a situation where it is impossible to make their energy consumption tie in with their energy budget,” the researchers write.
The team calls for further investigation into adaptive strategies and conservation policies that can help mitigate the risks sloths face in a rapidly warming world.
