The sloth populations of Central and South America could face a serious existential threat from climate change by the end of the century. New research published September 27 in the journal Peerj indicates that simply from a metabolic standpoint, Earth’s rising temperatures could pose a serious threat to the overall species’ health and long-term survival rates.
Led by Rebecca Cliffe, a zoologist and founder of The Sloth Conservation Foundationexperts focused their latest research on two-fingered sloths (Choloepus Hoffmanni), which live in both highland and lowland areas with a spectrum of average ambient temperatures. Using a methodology known as indirect calorimetry, Cliffe’s team analyzed the sloth’s oxygen consumption and core body temperatures in situations that reflected the warming rates projected for their habitats by 2100—some between 2-to-6 degrees Celsius (3 .6-to-10.8 degrees Fahrenheit). According to their study, the consequences are “expected to be profound.”
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“Sloths are inherently limited by their slow metabolism and unique inability to effectively regulate body temperature, unlike most mammals,” Cliffe explained in a associated statement. “Our research shows that sloths, particularly in high-altitude regions, may not be able to survive the significant increase in temperatures predicted for 2100.”
The biggest problems for higher altitude sloths stem from a sharp increase in resting metabolic rate (RMR) when confronted with warmer temperatures. This is especially problematic given their limited metabolic adaptability and difficulty finding cooler habitats. In contrast, although low-altitude sloths may be able to move to higher altitudes to find cooler homes, they still showed a biological survival trait called “metabolic depression” that limits further increases in RMR. This alone would pose its own threats to their health.
It’s not just sloth metabolisms that are worrisome, either. The animal’s digestion can be as much as 24 times slower than herbivores of the same size. This means they can’t simply eat more food as both global temperatures and metabolic rates rise.
Cliffe’s team admits in the study that their climate model was “rudimentary in omitting errors and uncertainty considerations.” Despite this, they predict “that a relatively small increase in ambient temperature at high altitudes could see sloths pushed into a situation where it is impossible to match their energy consumption with their energy budget.” It is this delicate balance between metabolism, digestion and habitat temperatures that makes the slow-moving species especially susceptible to the effects of climate change.