APPEARANCE
The sloth (Bradypus sp.) is a strong contender for the title of Weirdest Amazon Animal. From a
distance, it might be mistaken for a giant fruit or an ants' nest, especially because most of the time, it
remains motionless; the sloth attaches to a chosen resting spot and sleeps for four-fifths of its life (seems
like some teenagers I know!). The sloth's coloration is effective camouflage for an animal that wants to
look like a nest or fruit. It is covered with thick unkempt gray-green to brown fur which afford some
camouflage among the rainforest canopy tree crowns. During the one fifth of the time when it is actually
active, the sloth hangs upside down, from long gangly limbs equipped with two to three long curved claws; its
only defense. It moves through the trees with slow, measured movements, but is actually an adept swimmer, and
will drop into water if possible to escape predators, primarily the harpy eagle. The sloth has forward-facing
eyes and a small rounded snout, conferring upon it a primate-like appearance. But the sloth is not related to
the monkeys, and in fact lacks a tail (possessed by most primates). It belongs to a uniquely South American
group, the edentates, which inludes armadillos and anteaters, and so-called because of their primitive
dentition. The sloth is no exception. Although the sloth is a vegetarian, its teeth are poorly adapted to the
task, being peg-like stumps. (Most mammals have teeth which are highly differentiated to serve specific
purposes such as grasping, shearing and crushing.)
HABITAT AND DISTRIBUTION
The brown throated three-toed sloth (B. variegatus) is the commonest and most widespread of four
species found in Amazonia (a fifth species, the maned three-toed sloth, B. torquatus, is found only in the
Atlantic rainforest on Brazil's southeast coast). It ranges throughout the lowland rainforest from
northern Argentina and Bolivia to western Venezuela and Central America. East of the Rio Negro and north of
the Amazon River, it is replaced by the pale-throated three-toed sloth (B. tridactylus). Sloths spend
virtually all their lives high in the forest canopy, preferring trees with high crowns bathed in sunlight. On
the ground, the sloth can barely walk and practically helpless. However, to escape arboreal predators it will
drop into water and swim away. Its ability to swim also makes the sloth quite able to migrate around lowland
forest areas where rivers thread their way among the trees. High in the canopy where the sloth has slept
overnight, it warms itself in the morning, and when awake, slowly moves around to look for food. (I bet that
sounds like someone you know! :) They seem to reach their highest population numbers in dense secondary
forest (rather than primary rainforest). These habitats have a high proportion of new leaves favored by
sloths and the main predator, the harpy eagle is quite rare in secondary forest.
FEEDING AND DIET
Sloths are strictly herbivorous, and quite particular about what they eat—leaves and only leaves. They
feed on many species of trees, but also avoid many. Among their favorite food trees is cercropia (see photo), a common riverside
tree. This tree is protected from most herbivores by vicious stinging ants. The sloth, however, seems
unperturbed by the ravaging insects. (Perhaps its silky fur makes it hard for the ants to attack, or maybe
there are oils in the sloth's skin that inhibit attack. Sloths usually feed high in the canopy so stands of
cercropia, which is relative low-growing, are ideal to spot these creatures. Uniquely for an arboreal animal,
the sloth descends to the ground to defecate! The reason is not entirely clear, but the act is performed only
once a week. They climb down the tree, to the base, and dig a hole with their short stubby tail. After
defecation, the tail is used to fill the hole, presumably to prevent the odor from alerting nearby
predators.
BREEDING
Due to their inaccesibility, sloths do not make great subjects for scientific study. So not much is known
about the details of their reproduction. After mating, and gestation of about six months, a single young
is born. For six to nine months, the offspring is carried by the mother. The baby sloth clings to her
belly (riding on top) and when strong enough ventures off to climb branches without her help. From its
mother, the young sloth learns the best food plants and how to move around within her home range. A
strong bond between the mother and baby help the sloth get started in its complex arboreal world. It
stays in contact with the mother by calling, even after it has left her home range.
CONSERVATION
Sloths are in pretty good shape from a conservation stand-point. Their generalist diet means they can
adapt to reforested areas, and they can thrive in city gardens and parks where they are released after
being captured by people. Sloths are the most abundant large mammal in the canopy, comprising up to a
third of the biomass. It's the mammal most likely to be seen in the wild by visitors to the Amazon.
Although widely hunted by people it is hard to see, and manages to survive heavy hunting
pressure. When its habitat is destroyed by clear-cutting or flooding due to dams, huge numbers are
found. The destruction of habitat remains the greatest threat to sloth populations.
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