Extinct ground sloth likely ate meat with its veggies
New study reveals that Mylodon was an omnivore, unlike its strictly plant-eating relatives

Date:
October 7, 2021
Source:
American Museum of Natural History
Summary:
A new study suggests that Mylodon -- a ground sloth that lived in
South America until about 10,000 to 12,000 years ago -- was not
a strict vegetarian like all of its living relatives. Based on
a chemical analysis of amino acids preserved in sloth hair, the
researchers uncovered evidence that this gigantic extinct sloth
was an omnivore, at times eating meat or other animal protein in
addition to plant matter.



FULL STORY ==========================================================================
A new study led by researchers at the American Museum of Natural History suggests that Mylodon -- a ground sloth that lived in South America
until about 10,000 to 12,000 years ago -- was not a strict vegetarian
like all of its living relatives. Based on a chemical analysis of amino
acids (fundamental biological compounds that are the building blocks of proteins) preserved in sloth hair, the researchers uncovered evidence
that this gigantic extinct sloth was an omnivore, at times eating meat
or other animal protein in addition to plant matter. The study, published
today in the journal Scientific Reports, contradicts previous assumptions
in the field.


========================================================================== "Whether they were sporadic scavengers or opportunistic consumers
of animal protein can't be determined from our research, but we now
have strong evidence contradicting the long-standing presumption
that all sloths were obligate herbivores," said lead author Julia
Tejada, a Museum research associate and postdoctoral researcher at
the University of Montpellier, France. Tejada began the work on this
study as a Ph.D. student in the Museum's Richard Gilder Graduate School collaborative program with Columbia University.

Even though the six living sloth species all are relatively small
plant-eating tree-dwellers restricted to tropical forests of Central
and South America, hundreds of fossil sloth species, some as large
as an elephant, roamed ancient landscapes from Alaska to the southern
tip of South America. Mylodon darwinii, also known as "Darwin's ground
sloth," is thought to have weighed between 2,200 and 4,400 pounds and was nearly 10 feet long. Based on dental characteristics, jaw biomechanics, preserved excrement from some very recent fossil species, and the fact
that all living sloths exclusively eat plants, Mylodon and its extinct relatives have long been presumed to be herbivores as well. But these
factors could not directly reveal whether an animal might have ingested
food that requires little or no preparation and is completely digested,
as happens in carcass scavenging or some other kinds of meat-eating.

To get a more complete picture, the new study uses an innovative
approach based on nitrogen isotopes locked into specific amino acids
within animal body parts, known as "amino acid compound-specific isotope analysis." Found in different proportions in the food consumed by an
animal, stable nitrogen isotopes are also preserved in their body tissues
-- including hair and other keratinous tissues like fingernails, as well
as in collagen like that found in teeth or bones. By first analyzing
the amino-acid nitrogen values in a wide range of modern herbivores
and omnivores to determine a clear signal of eating a mix of plant and
animal food, fossils can then be measured to determine the food they
consumed. This offers paleontologists a unique window directly into
the diets of animals, enabling them to determine their "trophic level"
-- whether they were plant-eating herbivores, mixed-feeding omnivores, meat-eating carnivores, or specialized marine animal consumers.

"Prior methods relied solely on bulk analyses of nitrogen and complex
formulas that have many untested or weakly supported assumptions. Our analytical approach and results show that many previous conclusions
about tropic levels are poorly supported at best, or clearly wrong and misleading at worst," said study co-author John Flynn, Frick Curator of
Fossil Mammals in the Museum's Division of Paleontology.

The researchers used samples from seven living and extinct species of
sloths and anteaters (which are closely related to sloths), as well as
from a wide range of modern omnivores, from the scientific collections
of the Museum's Mammalogy and Paleontology Departments and from the Yale Peabody Museum. While the other extinct sloth in the study, the North
American ground sloth Nothrotheriops shastensis, was determined to be
an exclusive herbivore, the data clearly flagged Mylodonas an omnivore.

Prior research speculated that there were more herbivores than could be supported by the available plants in ancient ecosystems of South America, suggesting that some of those herbivores may have been finding other
sources of food. This new study provides compelling evidence supporting
that previously untested idea.

"These results, providing the first direct evidence of omnivory in an
ancient sloth species, demands reevaluation of the entire ecological
structure of ancient mammalian communities in South America, as sloths represented a major component of these ecosystems across the past 34
million years," Tejada said.

Other authors on this study include Ross MacPhee, from the American Museum
of Natural History; Tamsin O'Connell from the University of Cambridge;
Thure Cerling from the University of Utah; Lizette Bermudez and Carmen
Capun~ay from the Huachipa Zoo in Lima, Peru; and Natalie Wallsgrove
and Brian Popp from the University of Hawai'i at Manoa.

This work was funded by The Frick Fund (Vertebrate Paleontology, American Museum of Natural History), the Lamont Doherty Earth Observatory's
Chevron Student Initiative Fund, the Paleontological Society, and the
School of Ocean and Earth Sciences of the University of Hawai'i at Manoa.

========================================================================== Story Source: Materials provided by
American_Museum_of_Natural_History. Note: Content may be edited for
style and length.


========================================================================== Journal Reference:
1. Julia V. Tejada, John J. Flynn, Ross MacPhee, Tamsin C. O'Connell,
Thure
E. Cerling, Lizette Bermudez, Carmen Capun~ay, Natalie Wallsgrove,
Brian N. Popp. Isotope data from amino acids indicate Darwin's
ground sloth was not an herbivore. Scientific Reports, 2021; 11
(1) DOI: 10.1038/s41598- 021-97996-9 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/10/211007101025.htm

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