Megatherium - Paleobiology

Paleobiology

The giant ground sloth lived mostly in groups, but it may have lived singly in caves. While mostly herbivorous, it has been suggested that it may have used its size and strength to take over the kills of sabre-toothed cat Smilodon and to scavenge or hunt large, armored glyptodonts. For millions of years, the sloth had no enemies to bother it, so it was probably a diurnal animal.

The giant ground sloth was a herbivore, feeding on leaves such as yuccas, agaves, and grasses. While it fed chiefly on terrestrial plants, it could also stand on its hind legs, using its tail as a balancing tripod, and reach for upper growth vegetation. It would pull itself upright to sit on its haunches or to stand and then tugged at plants with its feet, digging them up with the five sharp claws on each foot. The sloth used its simple teeth to grind down food before swallowing it, and its highly developed cheek muscles helped in this process. The sloth's stomach was able to digest coarse and fibrous food. It is likely that it spent a lot of time resting to aid digestion.

A recent morpho-functional analysis indicates that M. americanum was adapted for strong vertical biting. The teeth are hypsodont and bilophodont, and the sagittal section of each loph is triangular with a sharp edge. This suggests that the teeth were used for cutting, rather than grinding, and that hard fibrous food was not the primary dietary component.

While it has been suggested that the giant sloth may have been partly carnivorous, this is a controversial claim. Richard Fariña and Ernesto Blanco of the Universidad de la República in Montevideo have analysed a fossil skeleton of M. americanum and discovered that its olecranon - the part of the elbow to which the triceps muscle attaches - was very short. This adaptation is found in carnivores and optimises speed rather than strength. The researchers say this would have enabled M. americanum to use its claws like daggers. They suggest that to add nutrients to its diet, Megatherium may have taken over the kills of Smilodon. Based on the estimated strength and mechanical advantage of its biceps, it has been proposed that Megatherium could have overturned adult glyptodonts (large, armored xenarthrans, related to armadillos) as a means of scavenging or hunting these animals. However, other zoologists have described this proposal as "fanciful".