The Mantled Howler Monkey is a type of New World monkey from
Central and South America in Colombia, Costa Rica, Ecuador, Guatemala,
Honduras, Mexico, Nicaragua, Panama and Peru. They live in several
different types of forest, including secondary forest and semi-deciduous
forest but are found in higher densities in older areas of forest
and in areas containing evergreen forest. They eat large quantities
of leaves; it has several adaptations to this folivorous diet. They
possess large salivary glands that help break down the leaf tannins.
The leaves and fruit from Ficus trees tend to be their preferred
source but flowers can also make up a significant portion of the
diet. They satisfy their water needs by drinking from tree holes
during the wet season and sourcing water trapped in bromeliads.
The fact that they rely so heavily on a low energy food sources
drives much of their behaviour--for example, howling to locate other
groups and spending a large portion of the day resting. They are
primarily black except for a fringe of yellow or golden brown guard
hairs on the flanks of the body earning the common name "mantled"
howler monkey. The infant's fur is silver at birth, but turns pale
or gold after a few days and then darkens until the infant takes
on the adult coloration at about 3 months old. They are one of the
largest Central American monkeys, and males can weigh up to 9.8
kg while females generally weigh between 3.1 and 7.6 kg. They live
in groups of 10 to 20 members, generally 1 to 3 adult males and
5 to 10 adult females, but some groups have over 40 members. Grooming
activity in the mantled howler is infrequent and has been shown
to reflect social hierarchy, with dominant individuals grooming
subordinates. Males outrank females, and younger animals of each
gender generally have a higher rank than older animals. Higher-ranking
animals get preference for food and resting sites, and the alpha
male gets primary mating rights. Females become sexually mature
at 36 months, males at 42 months. They undergo a regular estrus
cycle, with an average duration of 16.3 days, and display sexual
skin changes. The copulatory sequence begins when a receptive female
approaches a male and engages in rhythmic tongue flicking. The male
responds with the same tongue movements before the female turns
while elevating her rump, which allows for mating to begin. The
gestational period is 186 days; births can occur at any time of
year. The infant is carried under its mother, clinging to its mother's
chest, for the first 2 or 3 weeks of its life. After that, it is
carried on its mother's back. The male mantled howler has an enlarged
hyoid bone, a hollow bone near the vocal cords, which amplifies
the calls made by the male, and is the reason for the name "howler".
Howling allows the monkeys to locate each other without expending
energy on moving or risking physical confrontation. They also use
non-vocal communication, such as "urine rubbing" when in a distressful
social situation. They rub their hands, feet, tail and/or chest
with urine and mark their scent by rubbing its throat on branches.
Genital displays are used to indicate emotional states, and group
members shake branches, which is apparently a playful activity.
The mantled howler is usually indifferent to the presence of humans.
However, when it is disturbed by people, it often express its irritation
by urinating or defecating on them. It can accurately hit its observers
despite being high in the trees. They are regarded as vulnerable
and their numbers are adversely affected by rainforest fragmentation
which has caused forced relocation of groups to less habitable regions,
as well as deforestation and capture for the pet trade. They are
protected from international trade under Appendix I of the Convention
on International Trade in Endangered Species.