into southern Mexico; the Black Spider Monkey (A.
paniscus), which has two population centers, one east
of the Río Negro and north of the Amazon and one in
western Amazonia west of the Rio Madeira; and the
White- bellied Spider Monkey (A. belzebuth; plate 16-
13), once found widely southeast of the Amazon as
well as northwest of it in parts of Peru, Colombia, and
Venezuela, but now listed by the IUCN as endangered.
Spider monkeys are large but slender (hence the name),
generally weighing about 6.4 kg (14 lb). Their prehensile
tails range up to 90 cm (35 in) in length. They vary in
color from black to pale brown to reddish. Troops of
spiders typically consist of about eight adult males, 15
adult females, and 10 babies and juveniles. At any given
time, four females will be either pregnant or in estrus.
Bachelor male troops also occur. Often fewer animals are
seen together, because troops frequently fractionate in a
given area during the day, reassembling at their sleepingtree at night. Spiders forage together in the treetops, often
quite actively. Their slender bodies adapt them well for
graceful movement through the canopy, and they seem
to prefer mature forest. Spider monkeys often move by
brachiation, swinging arm over arm from branch to
branch in a manner similar to Old World gibbons. As
discussed in chapter 11, spider monkeys feed heavily on
fruits, though they also consume some leaves.
One of the most endangered Neotropical monkeys
is the Southern Woolly Spider Monkey, or Muriqui
(Brachyteles arachnoides), an inhabitant of the
threatened coastal forest of southeastern Brazil. It
is estimated that only 300 to 400 of these creatures
remain, scattered widely in fragments of what was at
one time continuous forest. As is the case with some
other endangered species, this animal was initially
hunted for food and is now mostly threatened by
habitat loss.Scared Monkeys and Angry Monkeys
It is insightful to contrast primate behavior in areas
where the animals are hunted regularly to behavior in
areas in which they enjoy complete protection. Where
they are hunted, monkeys become fearful and wary,
attempting to remain out of sight in the canopy when
humans approach. Near Manaus, Brazil, capuchins
have apparently learned to descend to the ground
so as to run through underbrush and avoid hunters.
In unprotected forests where monkeys are regularly
shot for food, I have seen troops of spider monkeys
frantically dash through the canopy, apparently
attempting to avoid the humans below. However, in a
protected forest near Alta Floresta, Brazil, south of the
Amazon, the presence of my group actually attracted
a troop of White- bellied Spider Monkeys, which
behaved belligerently, approaching us quite closely
in the forest, climbing into the understory and lower
canopy, vigorously shaking branches, loudly vocalizing,
and eventually urinating and defecating on us. These
monkeys do not normally encounter humans and
apparently regarded us as invaders into their territory.
Similar accounts are common where monkeys and
humans infrequently meet. It was a fulfilling experience
to see these animals so closely— though prudent to
wear a hat.In places where monkeys and humans do frequently
meet, but where monkeys are protected, the monkeys
do not act aggressively toward humans but seem to
view us as we view them, curiosities of nature (plate
16- 14).Monkey species are hunted to varying degrees
throughout Amazonia, where several of the larger species
are important food sources for indigenous people. In
general, where human populations are low, monkey
hunting is usually not so severe as to markedly deplete
the primate populations. Where human populations are
dense, local monkey populations may be significantly
reduced, and monkeys try hard to avoid humans.
It is obvious that the most important considerations
in maintaining primate populations is to assure the
presence of large tracts of natural forest accompanied
by freedom from hunting pressure.Plate 16- 14. These two— note the face at the bottom of
the photo— Mantled Howler Monkeys show no fear of our
group. They occupy an area in Panama where they are free
from local hunting pressure and are also frequently exposed
to people, so they do not act aggressively. Photo by John
Kricher.chapter 16 from monkeys to tarantulas: endless eccentricities 325