Inzoology, afolivore is aherbivore that specializes in eatingleaves. Mature leaves contain a high proportion of hard-to-digestcellulose, less energy than other types of foods, and often toxic compounds.[1] For this reason, folivorous animals tend to have longdigestive tracts and slowmetabolisms. Many enlist the help ofsymbiotic bacteria to release the nutrients in their diet. Additionally, as has been observed in folivorous primates, they exhibit a strong preference for immature leaves which tend to be easier tomasticate, are higher in energy and protein, and lower in fibre andpoisons than more mature fibrous leaves.[1]
It has been observed that folivory is extremely rare among flying vertebrates.[2] Morton (1978) attributed this to the fact that leaves are heavy, slow to digest, and contain little energy relative to other foods.[2] Thehoatzin is an example of a flighted, folivorous bird, but it is a weak flier, due to the well-developed foregut (used to digest its food) reducing the area available for flight muscles to attach.[3] There are, however, many species of folivorous flying insects.
Somebats are partially folivorous; their method of deriving nourishment from leaves, according to Lowry (1989), is to chew up the leaves, swallowing thesap and spitting out the remainder.[4]
Arboreal mammalian folivores, such assloths,koalas, and some species ofmonkeys andlemurs, tend to be large and climb cautiously.[5] Similarities in body shape and head- and tooth-structure between earlyhominoids and various families of arboreal folivores have been advanced as evidence that early hominoids were also folivorous.[5]
Standardecological theory predicts relatively largegroup sizes for folivorousprimates, as large groups offer better collective defense against predators and they face little competition for food among each other. It has been observed that these animals nevertheless frequently live in small groups. Explanations offered for this apparent paradox include social factors such as increased incidence ofinfanticide in large groups.[6]
Folivorous primates are relatively rare in theNew World, the primary exception beinghowler monkeys. One explanation that has been offered is that fruiting and leafing occur simultaneously among New World plants. However a 2001 study found no evidence for simultaneous fruiting and leafing at most sites, apparently disproving this hypothesis.[7]
Examples of folivorous animals include:
