Asian Apes
The smallest and the most
arboreal apes are the 12-13 species of gibbons. Because
of their diminutive size, these members of the family
Hylobatidae
are also referred to as the "lesser apes."
Most adult gibbons
are only about 3 feet (90 cm.) tall standing upright and 12-20
pounds (5.5-9 kg.) in weight.
Males in the biggest gibbon species, known as siamangs
,
are up to 30 pounds (13.5 kg.) and have longer arms.
Siamangs are different enough from other gibbons to be in their own genus.
All gibbons are very slender. Long bushy hair on their
bodies makes them look stockier than they actually are.
Unlike all of the larger ape species, gibbons have little sexual
dimorphism in body size.
The long arms, permanently curved fingers, and light
bodies of gibbons make them
excellent brachiators
. That is, they move
around in trees by swinging under branches with a hand over hand motion.
This is also referred to as suspensory climbing. At times,
gibbons also walk
bipedally, or two footed, on top of branches. However, they are more
efficient at brachiation, and 90% of their locomotion is by this means.
Each
swing can transport a gibbon 20 feet (6 m.)
at speeds approaching 35 miles (56 km.) an hour.
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Siamang
brachiating |
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| Gibbon |
Gibbons are monogamous
in their mating
patterns and form nuclear family groups. That is to say, their communities
consist of a single mating pair of adults with their juvenile offspring. They live in
well defined territories in the tree tops and rarely go down to the forest floor.
Adults regularly defend their territory against others of their species with
piercingly loud whooping and hooting vocalizations, much like the indris of Madagascar and
the howler monkeys of the New World. Though the calls
of the latter two primates sound very different. The calls of
different gibbon species are different from each other as well.
Orangutans
are the largest and the rarest of the Asian apes. Males
often grow to
175-200 pounds (80-90 kg.) and 4½ feet
(1.4 m.) tall. At this size, they are usually too large to cross from
one tree to another by the branches and must go down to the ground and walk
quadrupedally between them.
There is marked sexual dimorphism among the orangutans.
Males have huge fleshy pads framing the upper part of their faces.
In addition, females weigh
only about half as much as the males
(73-99 lbs or 33-45 kg.). Being lighter, females and juveniles often stay in
the trees and use a leaning form of brachiation--they carefully shift their body weight to
bend a supporting branch and then grab the next one before the first one breaks.
Orangutans
are intelligent and generally peaceful animals. Most
of the time, they live solitary lives browsing fruits and leaves.
Some also create simple stick tools to get honey out of bee hives in tree
crevices.
Unfortunately,
the orangutans are in danger of extinction in the wild because they are hunted for the
illegal international pet trade. Their forest territories are also being rapidly cut
down for the lumber and cleared by burning for farming, especially in Indonesia where
most of them live. According to Conservation International, the 15,000
remaining Indonesian orangutans are currently disappearing at a rate of 1,000 per
year. When population size decreases, there is a
corresponding decrease in genetic diversity. Species that have little
genetic diversity are more easily driven to extinction by a changing
environment. The loss of habitat has decimated gibbons in Indonesia as well. However, they are not at as much a risk
of becoming extinct because their range extends widely over Southeast Asia.
African Apes
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| Male lowland
gorilla |
The largest apes are the
gorillas of Africa. Adult males are up to 6 feet
(1.8 m.)
tall and have 9-10 foot (2.7-3.0 m.) arm spans. They have massive heads with heavy, thick muscles
on top that are used to close crushing jaws. Their bodies are stout and very
muscular.
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Knuckle walking
(subadult male lowland gorilla)
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Like humans, gorillas are
terrestrial animals. They are
quadrupedal
knuckle walkers. That is, they walk
on the soles of their feet but not on the palms of their hands.
They bend their fingers and support the
head end of their
bodies with their knuckles instead of their open palms.
They are
shy, peaceful vegetarians who live in family groups consisting of a dominant adult male
with several adult female mates and their children. Subadult males are tolerated in the family as long as they are not actively competing with the
dominant male for mates. Gorillas are also very sexually dimorphic
.
Adult males average about 350 pounds (160 kg.) and reach 400
pounds (181 kg.) in the wild,
while most adult females are only
about 155 pounds (70 kg.) and much less muscular.
There are
three varieties, or subspecies, of gorillas. The rare mountain gorillas live at high
altitude in sparse woodlands in the mountains of Central Africa, while the more
numerous lowland gorilla varieties live in the dense forests of West Africa.
Most zoo
gorillas are of the lowland varieties.
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Female lowland gorilla |
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| Common chimpanzee
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Peaceful allogrooming
(common chimpanzees) |
The
common chimpanzees
more closely resemble humans than do the gorillas. Male chimps grow to 5½ feet
(1.7 m.) tall
and average about 100 pounds (45 kg.) with 6 foot
(1.8 m.) arm spans, while females are
usually only around 82 lbs. (37 kg.) and are less muscular. However, like the other large apes,
chimpanzees are more comfortable getting around quadrupedally. They are
also knuckle walkers like
gorillas. The natural habitat of chimpanzees includes both tropical forests and
bordering savannas
in Africa.
Chimps are
intelligent animals with generally pleasant personalities. However, the males are
less peaceful than the smaller females. This behavior difference is typical of most
primate species, including humans. The chimpanzee diet is usually at least 90% vegetarian. Males
are more likely to eat meat than are females, although chimp hunting skills are
relatively poor.
Chimpanzees
live in fluid societies of 10-50 individuals. Membership changes through time as
females move from one community to another. Males usually stay together and act as a
group in defending their mutual territory. However, within each community, males
frequently establish short-term alliances in order to compete for dominance.
Chimpanzees do not form monogamous mating bonds. Females usually mate with
different males throughout their lives.
Bonobos
are close relatives of common chimpanzees in the same genus, Pan
.
They are sometimes referred to as pygmy
chimpanzees. Despite this name, they are only slightly smaller than the common
chimps. Bonobos usually have blacker hair with tufts at the side of their faces, longer
arms and legs, as well as slimmer bodies.
Their vocalizations are also quite different from those of the common
chimpanzees. Like many of the Old World monkey species, adult female bonobos
normally have prominent "sexual skins." However, unlike monkeys, bonobo
females are sexually receptive most of the time and have large sexual skins
throughout the year.
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| Female
bonobo |
Bonobo
sexual skin |
Bonobos have fluid social groupings
similar to the common chimpanzees, although bonobos are less excitable and aggressive.
Male-female alliances also are more important for bonobos. Older females at times
even become group leaders. Bonobos are unique among
nonhuman primates in primarily engaging in sexual intercourse face to face.
Gorillas do it occasionally. Both heterosexual and homosexual intercourse are common
among bonobos. Copulation occurs
frequently as a means of reducing tension in the community
and has become recreational for them. In this and
other traits, bonobos are like humans.
Today, the bonobo
range is limited to the forests south of the Zaire River in West Central
Africa, and there are considerably fewer of them than the
common chimpanzees.
Chimps and Bonobos--an explanation of how
they became different species
This link takes you to a
video at an external website. To return here, you must click
the
"back" button on your browser
program.
(length = 3 mins, 47 secs) |
Common
chimpanzees are the most successful of all apes in that there are more
of them and they have the widest geographic range. However, their
numbers have been significantly reduced. A century ago, there were
millions of them in the wild. Today, there are less than 200,000.
This sharp decline apparently has been mostly due to the rapid increase in
human populations and the accompanying natural habitat decimation. An
additional factor has been the desire of many people in
West and Central Africa
to eat
chimpanzees and other non-human primate species. At least 4,000
chimpanzees are killed for their meat every year.
Chimpanzees and gorillas have suffered devastating Ebola epidemics as
well. During 2002 and 2003, approximately 5,000 gorillas succumbed to
this highly contagious, almost always fatal disease. The bonobos are at an even greater risk of disappearing since there may be only
about 6,000 of them remaining in the wild.
Gorillas and both species of chimpanzees
have the misfortune of living in nations in which wildlife protection has been
severely disrupted by civil wars and the breakdown of
effective national authority over the last two decades.
It is unlikely that the populations of these apes would be able to spring back rapidly
even if they were more carefully protected because they have low
reproductive rates. Under the best conditions, adult female chimps
usually only have one baby every 5 years. The other great apes are
similar.
The great apes are not alone in being
threatened by humans. The World Conservation Union estimates that a quarter of all primate
species will go extinct within the next 20 years. Many
will disappear with little known about them.
