You’d think that two-toed sloths and three-toed sloths would be close cousins on the family tree. Well, maybe you’d think that if you weren’t a wildlife biologist.
In fact, the two types of sloths are not related at all and, yes, that baffles scientists who study them, including Dr. Tim Gaudin, UC Foundation professor in the Department of Biology, Geology and Environmental Science at the University of Tennessee at Chattanooga.
“It’s just one of those odd sort of accidents of evolutionary history,” said Gaudin, who has been a faculty member at UTC for the past 28 years. “We know nothing about their history, but they probably have been separate as long as sloths have been around—about 40 million years.”
Over professional development time in spring semester 2022, Gaudin took a deep look at the two types of sloths—both of which live in Central and South America—to try determining which of the 100 species of extinct sloths belong on the two-toed family tree and which were branches on the three-toed tree.
“Just to resolve those relationships, try to better understand those relationships and try to figure out who’s related to who,” said Gaudin, whose office houses several casts of sloth skulls, including one from 100,000 years ago when the animal was as big as an elephant, stood 15 feet tall and weighed about 13,000 pounds.
Gaudin and collaborators from North and South America and Europe have studied the issue for years but found no definitive answers.
During his professional development time, though, he was able to finish three academic papers he’d started but never been able to complete due to teaching and administrative duties at UTC.
“It was time to sit down and do analyses and finish up unfinished projects. I also was able to start one new project,” he said. “Without that time off, that wouldn’t have happened.”