New study shows that prehistoric sloths fed on animal meat

Modern sloths stay in trees, move at a slow pace and have a vegetarian diet, but the same cannot be said for their extinct relative, mylodon.

This ancient terrestrial sloth, which lived in South America until about 10,000 years ago, ate meat as well as plants, becoming omnivorous. The discovery, rooted in new research, contradicts previous scientific understanding of extinct giant creatures.

“Whether they were sporadic scavengers or opportunistic animal protein consumers cannot be determined in our research, but we now have strong evidence that contradicts the long-held assumption that all sloths were necessarily herbivores,” said lead author of the study, Julia Tejada, associate researcher at the American Museum of Natural History and postdoctoral fellow at the University of Montpellier, France, in a press release.

There are only six species of sloth alive today, and all of them can be found living in the trees of the tropical rainforests of South and Central America. However, the ancient land sloths were different. Some of them reached the size of elephants and lived in a wide variety of habitats, from Alaska to the tip of South America.

Study sloth, known as Darwin’s terrestrial sloth, or Mylodon darwinii, probably reached 3 meters in length and weighed between 1,007 and 1,996 kilograms.

Analyzes of jaws and teeth preserved as fossils of ancient sloths, as well as fossilized feces, have always suggested that mylodon and other extinct terrestrial sloths ate plants, like their modern relatives.

However, these clues do not reveal the whole story of what an animal ate during its lifetime, especially if that animal collected its food.

New evidence from chemical research

The researchers performed a chemical analysis of amino acids, the building blocks of proteins, which were preserved in the hairs of mylodon specimens. When an animal eats specific foods, nitrogen isotopes are trapped inside amino acids, which leave a trace inside body tissue such as hair, fur or nails, and collagen, which can be found in bones and teeth.

The nitrogen isotope signals can show whether an animal was a herbivore, carnivore, or omnivore.

In this case, the analysis revealed that the giant sloth ate both meat and plants. Researchers refer to the sloth as an “opportunistic omnivore,” meaning it may have fed on the carcasses of other animals or ingested animal protein from eggs.

In addition to studying the hair of mylodons, the researchers analyzed samples from seven species of sloth and their close relatives, living and extinct anteaters, for comparison. The team also studied a wide range of modern omnivores.

Another extinct sloth that scientists have studied, a terrestrial sloth called Nothrotheriops shastensis who lived in North America, was considered herbivore, but mylodon stood out as a clear omnivore.

Previous research suggested that there was not enough vegetation to support all the herbivores that lived in South America, so mylodon may have turned to other food sources. The new study supports this hypothesis.

“These results, providing the first direct evidence of omnivory in an ancestral sloth species, require a reassessment of the entire ecological structure of ancient mammal communities in South America, as sloths have represented an important component of these ecosystems for the past 34 million years,” said Tejada.

The study was published in October in Scientific Reports.

Translated text. Read the original in English.