The name "two-toed sloth" was intended to describe an anatomical difference between the genera
Choloepus and
Bradypus, but does so in a potentially misleading way. Members of
Choloepus have two digits on their
forelimbs (the thoracic limbs) and three digits on their
hindlimbs (the pelvic limbs), while members of
Bradypus have three digits on all limbs. Although the term "two-fingered" sloth is arguably less misleading, the shorter "two-toed" is much more widely used. Members of
Choloepus are larger than three-toed sloths, having a body length of , and weighing . Other distinguishing features include a more prominent snout, longer fur, and the absence of a
tail.
Behaviour Two-toed sloths spend most of their lives hanging upside down from trees. They cannot walk, so they pull hand-over-hand to move around, which is at an extremely slow rate. Almost all of their movement comes from this suspended upside down position, at a higher degree than even three-toed sloths. As a result, they tend to gravitate towards less vertical portions of trees. Being predominantly nocturnal, their fur, which grows greenish algae to blend in, is their main source of protection. Their body temperatures depend at least partially on the ambient temperature; they cannot shiver to keep warm, as other mammals do, because of their unusually low metabolic rates and reduced musculature. The mother gives birth to a single young, while hanging upside down. The young are born with claws, and are
weaned after about a month, although they will remain with the mother for several more months, and do not reach maturity until the age of three years, in the case of females, or four to five years, in the case of males.
Feeding They eat primarily
leaves, but also
shoots,
fruits,
nuts,
berries,
bark, some native
flowers, and even some small
vertebrates. In addition, when they cannot find food, they have been known to eat the
algae that grow on their fur for nutrients. They have also been observed using
mineral licks. They have large, four-chambered
stomachs, which help to ferment the large amount of plant matter they eat. Food can take up to a month to digest due to their slow metabolism. They get most of their fluids from water in the leaves that they eat but sloths have also been observed drinking directly from rivers.
Dentition and skeleton Two-toed sloths have a reduced, ever growing
dentition, with no
incisors or true
canines, which overall lacks homology with the dental formula of other mammals. Their first tooth is very canine-like in shape and is referred to as a caniniform. It is used for tearing small chunks off of their food, as well as for defense against predators. It is separated from the other teeth, or molariforms, by a
diastema. The molariforms are used specifically for grinding and are mortar and pestle-like in appearance and function. Thus, they can grind food for easier digestibility, which takes the majority of their energy. The
dental formula of two-toed sloths is: (unau) Two-toed sloths are unusual among mammals in possessing as few as five
cervical vertebrae, which may be due to mutations in the
homeotic genes. All other mammals have seven cervical vertebrae, other than the three-toed sloth and the
manatee.
Musculature Two-toed sloths generally have similar musculature to that of other mammals. This includes their
zygomaticus muscles, their superficial
masseter, their deep masseter, and their
medial and lateral pterygoids. Additionally, a specific section of their
anterior temporalis is arranged vertically, to allow them to sharpen their caniniform teeth. They tend to have stronger flexor muscles in their fore- and hindlimbs, as well as their shoulders. == Notes ==