When you're finished admiring a three-toed sloth's amazingly long nails, friendly face, and all together strange physical appearance, look closely into its fur, where it's carrying a mini-ecosystem of moths, beetles, and other insects largely responsible for why the mammal risks being eaten to defecate on the ground over the safety of the trees, National Geographic reported.
Fifty percent of three-toed sloth deaths occur on the ground during the act of defecation, according to Nat Geo's Ed Young. Yet, they continue to do so because of a natural instinct scientists believe is ultimately beneficial to both the animal and its legion of dependent insects.
In a new study by Jonathan Pauli of the University of Wisconsin-Madison, the researcher connects the behavior of three-toed sloths (he found two-toed sloths don't support the moths and are less likely to defecate on the ground) to a species of moth found only on their backs. When the sloth defecates, the moths lay their eggs on the feces, which the larvae rely on exclusively for food until they become moths and find suitable "sloth cloth" (I'll have to take credit for that coinage) to make an existence.
Meanwhile, having more moths in a sloth's fur is an indirect pathway to more food. Either by dying on the sloth or "providing nitrogen-rich waste from the dung pile," the moths are providing their host with more nitrogen, propagating another species present in sloth fur, algae, Nat Geo reported.
At this point, the rationale becomes more speculative. According to Pauli, the type of algae on sloths is a highly efficient food source; it has the same amount of carbohydrates and protein as leaves and three to five more times as much fat. But, Pauli and researchers aren't exactly sure how the sloth ingests it -- whether the animal licks it in through its fur or absorbs it through its skin.
"We never saw sloths behaving in a way that might suggest or indicate that they were somehow extracting algae or other nutrients from their fur," Brazilian researcher Adriano Chiarello told Nat Geo. "I don't remember ever seeing a sloth licking or lapping its fur."
"Perhaps sloths do this secretly, or solely at night when such behaviour would be even more difficult to witness," Chiarello rationalized, even though he still believes there is something missing in the research, or "the smoking gun."
Is it an evolutionary adaptive instinct that leads sloths to the ground? If so, why do so many get eaten during their trips? How are the algae being ingested?
"Testing hypothesis with sloths is not easy as they are difficult to capture and observe in their natural environment," Chiarello said. "The authors are making their best with available data."
