Sloths, the famously slow-moving yet charming creatures found in Central and South America, might face extinction by the end of the century due to the impacts of climate change.
A recent study has revealed alarming trends in how sloths respond to rising temperatures, highlighting their unique vulnerabilities.
The research, published in PeerJ Life & Environment, focused on two-fingered sloths living in both lowland and highland environments in Costa Rica.
Lead researcher Rebecca Cliffe and her team have spent 15 years studying sloths in this region, and the findings have raised significant concerns about sloths’ future survival.
“Despite being iconic species, comprehensive long-term population monitoring simply hasn’t been conducted at a scale that reflects the true challenges sloths face,” Cliffe Stated.
“In areas where sloths were once abundant, we have observed their populations completely disappear over the past decade.”
The study involved measuring oxygen consumption and core body temperature of sloths under simulated climate change conditions.
Findings indicated that sloths in high-altitude regions showed a sharp increase in their resting metabolic rate (RMR) as temperatures rose, pointing to greater energy demands.
Unfortunately, this increase may leave them unable to consume enough food to meet their heightened energy needs.
While lowland sloths have adapted better to warmer climates by entering a state of metabolic depression when temperatures get too high, this strategy only works to a certain extent.
Both lowland and highland sloths face considerable challenges if temperatures increase by the projected 2 to 6 degrees Celsius by 2100.
“Sloths are uniquely vulnerable to rising temperatures due to their physiological adaptations,” Cliffe explained.
“They survive on an extremely low-calorie diet, so conserving energy is critical for them.”
One way they conserve energy is by not actively regulating their body temperature as many other mammals do, a process that requires significant energy.
Adding to their plight, sloths’ digestion rates are incredibly slow—up to 24 times slower than similar-sized herbivores—making it difficult for them to increase food intake to balance the increased energy requirements caused by higher temperatures.
High-altitude sloths are particularly at risk because they have limited ability to migrate to cooler areas, being geographically constrained.
Unlike lowland sloths, which might shift their ranges to higher altitudes, highland sloths are left with few options.
The authors of the study acknowledge that further research is needed to fully understand sloths’ metabolic response to rising temperatures.
With a small sample size, there is room for some uncertainty and error.
However, Cliffe and her team stress the importance of developing conservation policies to mitigate the threats faced by one of the Americas’ most iconic mammals.
Ultimately, the survival of sloths across Central and South America will depend on how far temperatures rise.
“If climate change continues unchecked and these regions become uninhabitable, sloths may not have anywhere else to go,” Cliffe warned.
Sloths are creatures of habit, highly specialized in their habitats, and are not suitable for translocation to other regions.
If their environment becomes too hot, their survival is unlikely.