Now represented by only two living genera restricted to tropical forests, sloths once were a dominant group within South American ecosystems until as recently as 10 ka, right before the last ice age extinction. Fossil sloths are considered plant eaters, like their modern relatives, but their extremely high diversity suggests that these were ecologically more versatile than traditionally thought. Considering that sloths comprised an important proportion of South American mammalian diversity, evaluating their trophic relationships is crucial for understanding the evolution of Neotropical biodiversity as a whole. Stable isotope analyses, a technique based on the chemical composition of animal tissues, provides a more direct tool for reconstructing ecologies than indirect morphological indicators because the elements that organisms use to synthesize their tissues come from the ingested food.

This project aims to (1) rigorously test feeding behavior in fossil sloths, and (2) measure the patterning in diet-animal tissue amino acid d15N offsets in fossil sloths and modern mammals, to reliably determine feeding behaviours of extinct species using stable isotope data.