Observations of a die-off at such a pool inspired the idea that a group of ancient ground sloths might have died in a similar way.
Hippos congregate in large numbers in pools in Africa, contaminating them with feces. Lindsey then realized that the characteristically shaped plant material she'd found associated with the sloth bones had probably been cut by their teeth, and was either gut contents or feces - a large amount of it. "It created this very unsanitary environment and thus this contributed to this rapid development of this disease that ended up wiping out their population," she said. A large amount of feces concentrated in the water. Her colleague described how a drought had concentrated hippos around the small pond, and as a matter of course, the hippos defecated into it. "It wasn't until later when I was talking with a friend who is a retired professor of geography, and he told me a story that he had been monitoring a hippo wallow in Africa back in the '70s," she said. In and around the remains was a large amount of plant material - small branches, stems and twigs, all sharply cut into roughly 2.5-centimetre lengths.Īt first Lindsey didn't know what to make of this material. This seemed like a benign environment for giant sloths, so finding the remains of so many animals that had died at the same time was a mystery.įortunately the tar seep had preserved more evidence than bones. La Brea Tar Pits staff and Ecuadoran students excavate and collect giant sloth bones at the Tanque Loma tar pit locality in Ecuador. " probably had a lot of vegetation and it was probably an attractive area for large animals to come and spend time in otherwise still somewhat arid tropical environment." "We believe that the site was a spring-fed marsh," said Lindsey. The excavated bones turned out to be from at least 22 individual animals, from small, dog-sized infants to full-sized adults. The context in which the bones were found suggested the animals died at roughly the same time, and also revealed the nature of the location. "It's a site that probably formed not through large animals getting actually trapped in the tar, but from an asphalt seep that arose after a bone bed was deposited, and just fortuitously preserved the bone bed in situ."Įxcavations over a period of nearly two decades revealed that the tar seep had preserved various plant and animal remains. The most notable were hundreds of bones from one of the largest species of giant sloth that ever lived, known scientifically as Eremotherium laurillardi, which survived as a species for about five million years.Īdults of this species weighed upward of three tonnes and could reach a length of up to six metres. They were ground dwelling herbivores who could feed on foliage high in tree tops by rearing up on their powerful hind legs.
Researcher Emily Lindsey at the excavation site in Ecuador surrounded by sloth bones. The most famous similar site is Lindsey's research home - she's assistant curator and excavation site director at the La Brea Tar Pits in Los Angeles. But she said the preservation here is a little different. Giant ground sloth remains have been found in many locations in the Americas, but the find at a site called Tanque Loma in Ecuador in the early 2000s was unique. First uncovered by an oil company during exploration, the site was a "tar seep" in which plant and animal remains had been sealed in naturally occurring tar. "There were a lot of very large animals in that ecosystem and these sloths … were some of the largest." Seeping tar was the key to fossil preservation "Between 10,000 and 50,000 years ago, depending on which continent you're on, basically all ice-free continents had ecosystems that looked a lot more like a modern African ecosystem," said researcher Emily Lindsey in an interview with Bob McDonald on Quirks & Quarks. The largest species of giant ground sloths rivalled African elephants in size, and this new research suggests that their behaviour might have been very elephant-like as well. Giant ground sloths lived in North and South America for millions of years until their extinction around the end of the last ice age - about 11,000 years ago. An enormous pile of enormous bones excavated in Ecuador has given new insight into the behaviour of extinct giant ground sloths.
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