Although most of the terrestrial world is covered in trees, there are precious few vertebrates that make the canopy their home and subsist solely on a diet of leaves.
Tree sloths are among the most emblematic tree-dwelling mammals. However, they are best known for their pokey demeanor rather than the fact that they spend the majority of their lives in trees munching leaves. But the slow motion lifestyle of tree sloths, according to a new study, is the direct result of the animal’s adaption to its arboreal niche.
“Among vertebrates, this is the rarest of lifestyles,” says Jonathan Pauli, a University of Wisconsin—Madison professor of forest and wildlife ecology and the senior author of a report to appear in the August 2016 edition of the American Naturalist. “When you picture animals that live off plant leaves, they are almost all big — things like moose, elk and deer. What’s super interesting about arboreal folivores is that they can’t be big.”
Although most of the terrestrial world is covered in trees, there are precious few vertebrates that make the canopy their home and subsist solely on a diet of leaves.
Tree sloths are among the most emblematic tree-dwelling mammals. However, they are best known for their pokey demeanor rather than the fact that they spend the majority of their lives in trees munching leaves. But the slow motion lifestyle of tree sloths, according to a new study, is the direct result of the animal’s adaption to its arboreal niche.
“Among vertebrates, this is the rarest of lifestyles,” says Jonathan Pauli, a University of Wisconsin—Madison professor of forest and wildlife ecology and the senior author of a report to appear in the August 2016 edition of the American Naturalist. “When you picture animals that live off plant leaves, they are almost all big — things like moose, elk and deer. What’s super interesting about arboreal folivores is that they can’t be big.”
Pauli and Wisconsin colleagues M. Zachariah Peery, Emily Fountain and William Karasov set out to measure the energetics of wild two- and three-toed sloths at a field site in in northeastern Costa Rica. The purpose of the study, Pauli says, was to help explain why arboreal folivores are indeed so rare and why more animals have not evolved to take advantage of a widespread ecological niche.
“Most of the world is forested, but the energetic constraints of a leafy diet seem to prevent adaptive radiation,” Pauli notes, referencing the canon of evolutionary biology that helps explain the diversity of life on our planet: As organisms evolve and “radiate” from an ancestral group, they take on a variety of specialized forms that enable them to live a certain lifestyle or occupy a particular niche.
Continue reading at the University of Wisconsin-Madison.
Image credit: Zack Peery via the University of Wisconsin-Madison.
