Caves located in arid climates preserve ground sloth dung that is tens of thousands of years old. The shasta ground sloth (Nothrotheriops shastensis) ranged throughout the American southwest during the late Pleistocene and left telltale evidence of its diet in several of these caverns including Rampart Cave, Arizona; Shelter Cave, New Mexico; and Gympsum Cave, Nevada. From the macrofossils and DNA evidence in this dung we know this species ate a wide variety of plants–pine, mulberry, mustards, agave, yucca, grass, mint, globe mallow, saltbush, Mormon tea, grape, water leaf, creosote bush, hop sage, sagebrush, and willow. There is no evidence from these coprolites that ground sloths ate meat. Nevertheless, some scientists hypothesize ground sloths did scavenge meat . Although ground sloths were too slow to actively hunt most prey, they could have taken advantage of available carrion, and perhaps even usurped the kills of predators. Ground sloths were powerful beasts with long claws capable of severely injuring a carnivore contesting ownership of a carcass. Some scientists have even suggested ground sloths could have actively turned over glyptodonts to attack their vulnerable underbelly.
The lack of meat in known sloth coprolites doesn’t preclude the possibility they did on occasion eat animal protein. Over 99% of white-tail deer feces will show no evidence of flesh-eating. Yet, we know they do sometimes scavenge meat and even prey on nestling birds and eggs (See: https://markgelbart.wordpress.com/2012/05/11/unexpected-items-in-the-diet-of-the-white-tail-deer/) Without evidence the hypothesis that ground sloths ate meat is mere speculation. However, evidence from 1 specimen supports this hypothesis.
Artist’s rendition of a Megatherium, a large ground sloth that formerly lived in South America. The deer in the foreground is a pampas deer (Ozotoceros bezoarticus)), still extant but very rare.
Photo of a rib interpeted to have been gnawed on by a Megatherium. From the below referenced book.
A fragmentary rib in the collection of a museum in Uruguay has gnaw marks on it that match the teeth of Megatherium americana, a large ground sloth. The rib is from either another ground sloth or a mastodon. (Scientists can’t differentiate among these 2 species from just this part of the anatomy.) It has 7 shallow marks. Weathering marks exist over the tooth marks, eliminating the possibility that natural abrasions caused the scratches. The marks are too dull to have been the result of human cutting. The marks don’t match those of rodents or carnivores. However, they exactly match the “transversely bilophodont” teeth of a megatherium. The spacing of the tooth marks also match the distance between the bottom teeth of a megatherium. The scientist who examined the marks believes the sloth held the bone upside down and gnawed on it with its bottom teeth.
If sloths ate carrion, I’m sure they would have also eaten ground-nesting bird nestlings and eggs as well. They likely snacked on insects. Ground sloths are related to armadilloes and anteaters. Armadilloes eat carrion, small mammals, eggs, and insects. Ground sloths probably retained the ability to digest animal protein from their shared ancestry with armadilloes. The evolutionary ancestor of both lines was likely omnivorous. There’s no reason to assume ground sloths could not have taken advantage of an easy source of protein, though their diet was primarily vegetarian. This feeding strategy would not be unlike those of bears, hogs, and apes.
Farina, Richard; Sergio Vizcaino, and Gerry Del Iuliis
Megafauna: Giant Beasts of Pleistocene South America
Indiana University Press 2013
Poinar, Henrick; et. al.
“Molecular Coproscopy: Dung and Diet of the Extinct Ground Sloth, Nothrotheriops shastensis”
Science 281 (5375) 1998