Bones to tell tale of sloths in Southwest Iowa

IOWA CITY - University of Iowa researchers hope new evidence will soon prove three sloths found in southwest Iowa are from the same family.

UI researchers, students and volunteers have worked at a dig site near Shenandoah since 2003, helping unearth bones from four giant ground sloths representing two different species.

The UI Museum of Natural History wrapped up the dig in September this year, meaning they cleared all of the areas they thought might contain bones. Now they will focus on research of the bones, soil samples, pollen and data collected.

They hope DNA testing of the bones from one adult and two juvenile sloths of the same species found at the site will show they are related. That testing is being conducted now and should be concluded soon, Sarah Horgen, education coordinator for the Museum of Natural History, said.

“That's one of our big questions - trying to prove they were a family,” she said.

There are less than 200 recorded sites in the United States where sloth bones have been found, Horgen said. What makes the Iowa site especially important, she said, is the fact that the bones from numerous sloths were found there. Normally, sloth bones are found alone, leading researchers to believe they were solitary animals, she said.

If testing proves the three sloths from the Iowa dig site to be related, it would be a big discovery, Horgen said.

“We have the first family ever found, which we're hoping will tell us something about their social behavior,” she said.

Another big development this past year with the UI sloth project was the identification of one bone as being from a completely different species of sloth, Horgen said. Sloth expert Greg McDonald visited in May and determined that one of the bones in the UI collection belonged to a Paramylodon, a species never before found in Iowa. That also meant the workers had found bones of four different sloths representing two species, rather than bones of three sloths from the same species.

“That was a pretty big find,” Horgen said.

While the UI researchers concluded work at the dig site this fall, they would return if more bones are found.

“We think we've cleared a majority of the site,” Horgen said.

Landowners discovered sloth remains south of Shenandoah in 2001. They donated all of the bones found to the UI, to be used for educational research and study. The UI collection includes the second most-complete skeletons ever found of an adult sloth and of a juvenile sloth.

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