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While sloths are often seen as lazy creatures that spend their days napping in trees, recent research indicates that this behavior is key to their endurance.
Researchers have studied the evolutionary lineage of sloths, including those now extinct, known primarily from fossils.
Historical giant sloths on land became easy targets for early human hunters.
In contrast, smaller sloths residing in trees managed to survive.
Alberto Boscaini
The findings highlight the importance of conserving the remaining sloths on Earth, symbolizing only a fraction of 30 million years of evolutionary progress.
“Some sloths exist today, while others face extinction, and a key takeaway is we must act quickly to prevent the complete disappearance of this group,” stated Dr. Alberto Boscaini of the University of Buenos Aires, who spearheaded the research.
Presently, sloths are small, tree-dwelling creatures, celebrated for their charming appearances and leisurely pace, native to the rainforests of South and Central America.
Historically, however, a multitude of sloth species existed throughout the Americas, displaying various sizes and adaptations suited to diverse surroundings, some even reaching elephant size and standing taller than humans.
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However, about 15,000 years ago, sloths began to vanish. Researchers remain divided on the causes, which include human hunting, environmental changes, or a blend of both.
In the latest study, scientists examined body sizes of sloths through their evolutionary timeline, integrating genetic information.
They discovered sloths frequently altered their size in response to climate changes, though without lasting repercussions. Their “sudden and steep decline” aligns with the period humans were expanding across the Americas, hunting large animals for sustenance.
Larger terrestrial sloths likely became easy prey, and those populations diminished first, according to researchers.
Diego Barletta
In contrast, the smaller tree-dwelling sloths attracted less attention and have persisted through time.
“Modern sloths move slowly due to their low metabolic rate, which serves as their survival strategy,” noted Dr. Boscaini.
Co-researcher Dr. Daniel Casali from The University of São Paulo, Brazil, remarked, “While we can protect the surviving sloths, we sadly have lost elements that cannot be replaced.”
The findings are detailed in the journal, Science.