Woolly monkeys are a group of six species (genera
Lagothrix and Oreonax; plates 8- 13 and 16- 15) named
for their thick woolly fur, which may be black, brown,
grayish, or reddish, depending both upon species and
geographic location (there is much variation). The
Common Woolly Monkey (Lagothrix lagothricha)
ranges throughout western Amazonia. Woollies are
larger than spider monkeys, weighing up to 10 kg (22
lb), and in body shape they more closely resemble
howler monkeys (discussed below). Like howlers and
spiders, woolly monkeys have prehensile tails and are
highly skilled arboreal acrobats. They prefer mature
forest, where groups of between two and 60 monkeys
feed on fruits, palm nuts, seeds, foliage, and some
arthropods. They feed at varying heights, not being
confined to the canopy, and can be found in both
seasonally flooded and terra firme forests.
Woollies are intensively hunted, because the meat is
tasty and the animals themselves are large. They have
a generally low reproduction rate and cannot maintain
their populations against strong hunting pressure.
Howler monkeys (Alouatta spp.) are as large or larger
than woolly monkeys and are the most well studied
Neotropical monkeys. Many primatologists have
focused on howlers, including studies of their various
behaviors, troop sizes, communications, territoriality,
vocalizations, and feeding habits.
Howlers are large and robust monkeys with
prehensile tails and bearded faces. They are
widespread, distributed from the Amazon Basin south
to Argentina and Paraguay and north to Trinidad,
Central America, and the Yucatán Peninsula. There are
11 species, two of which are considered endangered.
The most widespread is the Red Howler Monkey,
historically known as A. seniculus and the subject of
much fieldwork. Recently the IUCN has split it into the
Guianan Red Howler Monkey (A. mcconnelli) and the
Bolivian Red Howler Monkey (A. sara), but be aware
that most of the descriptions in the literature were
written prior to the split and thus refer to it as the Red
Howler Monkey and A. seniculus. Red howlers of either
species are recognized by bright reddish fur, hence
the common name (plate 16- 16). Red howler species
occur throughout northern South America north of
the Amazon and east of the Andes, including Trinidad.
They are replaced south of the Amazon and throughout
central and eastern Brazil by the Red- handed Howler
(A. belzebul), which has all- black fur except on the
hands, feet, tail, and (on males) scrotum, where it is
rusty red. The Black Howler (A. caraya; plates 16- 17– 18)
is found in extreme southern Amazonia into Paraguay
and Argentina. It is sexually dimorphic in coat color,
the males being all black, the females tan. The Brown
Howler (A. guariba), whose coat color is uniformly
warm brown, is found in southeastern Brazilian coastal
forests and in northeastern Argentina, and, though not
yet considered endangered, it is experiencing rapid loss
of habitat. Both species of endangered howlers occur
largely (one entirely) in Middle America. The Mexican
Black Howler (A. pigra), an all- black species quite
similar in appearance to the Black Howler, is found
only on the Yucatán Peninsula, in Mexico, Belize, and
Guatemala. The Mantled Howler (A. palliata; plate
16- 14), essentially black but tan- brown on its sides
and back, is found west of the Andes from northern
Peru to Colombia and throughout Central America
to southern Mexico. Though this range is extensive
(and does not overlap with that of the Mexican Black
Howler), the populations have been reduced in some
places due to forest fragmentation.
Howlers are named for their loud and intimidating
vocalization, which echoes through the rain forest
mostly at sunrise and sunset (plate 16- 19). The sound
is more like a roar than a howl. Males have an enlargedPlate 16- 15. The Yellow- tailed Woolly Monkey (Oreonax
[Lagothrix] flavicauda) is found only in Andean humid
montane forests in Peru and is considered an endangered
species. Photo by Andrew Whittaker.326 chapter 16 from monkeys to tarantulas: endless eccentricities