Folivore

Mature leaves contain a high proportion of hard-to-digest cellulose, less energy than other types of foods, and often toxic compounds.

[2] Morton (1978) attributed this to the fact that leaves are heavy, slow to digest, and contain little energy relative to other foods.

[3] Arboreal mammalian folivores, such as sloths, koalas, and some species of monkeys and lemurs, tend to be large and climb cautiously.

Explanations offered for this apparent paradox include social factors such as increased incidence of infanticide in large groups.

However a 2001 study found no evidence for simultaneous fruiting and leafing at most sites, apparently disproving this hypothesis.