Let’s talk sloths. There are currently 6 known species of the Sloth all of which are herbivorous and all of them were thought to be herbivorous for a very long time. But new research suggests that our childhood friend, Sid, may have been a bit of a scavenger.
Darwin’s Ground Sloths, which were about 3 meters long and weighed approximately 2000 kilos, have always been considered vegetarians. However, the sampling of fossil hair has elucidated quite the opposite. But before we delve into the research and results it’s important to understand isotopes.
Yes; isotopes have the same number of protons and a different number of neutrons- they are variations of the same element. Now some of these isotopes are radioactive- they are unstable and release sub-atomic particles, which we can, thanks to technology, detect. Nitrogen, a key component of amino acids and, yes, proteins, also forms unstable isotopes. Another thing to grasp is that these Nitrogen isotopes in certain amino acids, such as Glutamine, change the higher up the food chain the animal is in. Other amino acids, such as Phenylamine, are unaffected by the hierarchy of an organism in the food chain but can be affected by the environment.
Coming to the research, scientists at the University of Montpellier, France recently examined the make-up of these 2 amino acids in two species of extinct sloths. The Glutamine of Darwin’s Ground Sloth did contain high radioactivity. However, this could be either due to the environment or the nutrition of the sloth. So which is it?? Well, the Phenylamine is unaffected by what is ingested by the organism and can thus act as a control. Given this, the researchers found that the level of isotopic N of this amino acid was at the baseline, thus indicating that the environment does not cause the radioactivity- the nutrition does. This indicates that the sloths were omnivores or even scavengers. To back their results, the researchers compared Radioactive Nitrogen Levels in omnivores from the present: anteaters, sloths, and many others.
This research helps account for the lack of large predators in South America during the Ice Age. But it is not the fact that Sloths were meat-eaters that makes the research interesting. It is the fact that the method applied to this discovery is a revolutionizing step in the field of Paleontology. Before this technique, a complex (and, now, redundant) equation was used to ascertain tropic levels. This goes to show that a little bit of knowledge and a whole bunch of creativity may be the key to scientific revolution.
Article:
Tejada, J.V., Flynn, J.J., MacPhee, R. et al. Isotope data from amino acids indicate Darwin’s ground sloth was not an herbivore. Sci Rep11, 18944 (2021). https://doi.org/10.1038/s41598-021-97996-9
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