Download Black-and-white Ruffed Lemur: Size: Head and body 51

Black-and-white Ruffed Lemur:
Size: Head and body 51-60cm, tail a little longer, 3.2-4.5kg, scent glands on
feet and backside.
Lifespan: 15-20 years in captivity.
Babies: Babies in litters, 50% twins, up to 6 babies once a year; female has 6
nipples. Gestation 90-102 days (short for such a large lemur!), weaned in 135
days. Females mature at 20 months.
Social life: Monogamous pairs or groups of 5-16. The dominant female
defends the group and leads.
Distribution: Madagascar.
Habitat: Only in mountainous rainforests on the eastern coast. Duke Primate
Centre has a map of their distribution.
Classification: The Ruffed Lemurs are in their own genus Varecia separate
from the other Eulemurs because of their unique reproductive behaviour. There
are two subspecies of Ruffed Lemurs, the Red Ruffed
Diet: Black and White Ruffs eat mainly fruits and are active mainly in the
evening, waking at dusk and feeding in the first half of the night. They also
snack on leaves, shoots, seeds, nectar and may even eat soil.
Reproduction: Babies are born in the wet season when food is plentiful.
Ruffed Lemurs are the only lemurs to have litters of babies, usually 3, but up
to 6 at a time. Unlike other primates, females have 3 pairs of nipples so she can
nurse them all at the same time! Unlike other lemurs, the mother builds a nest
for her babies (lining it with fur pulled from her own body) and does not carry her babies. She stays with them for
the first 2 weeks and later leaves them in the nest while she forages for food. Ruffs have been seen chasing off
birds of prey and confronting carnivores on the ground, perhaps to distract them from a nest of young. To move
her babies to another nest, the mother carries them one by one in her mouth like a mother cat and her kittens.
Babies are not blind or naked but still quite helpless. The babies can climb to the canopy top by 5 weeks and
move on their own by 7 weeks.
Black-handed/Golden Spider Monkey
Spider monkeys are so named because of
their long, spidery limbs. Their prehensile tail
acts like a fifth limb when swinging through the
canopy.
Subspecies: Nine.
Life span: Unknown.
Statistics: Head and body length: 30-63cm,
Tail length: 59-84cm, Weight: Females: 68.9kg, Males 7.5-9kg.
Physical Description: Spider monkeys have
distinctly long, slender limbs, and a long
prehensile tail with a hairless area on the
underside. The fur is gold-brown or red to dark
brown and they have black hands and feet.
Distribution: Black-handed spider monkeys
range throughout Central America from
Veracruz (Mexico) to west Panama.
Habitat: They inhabit rainforest, semi-deciduous forest and mangrove forest.
Diet: Black-handed spider monkeys mainly feed on fruit, but they also eat leaves, seeds, flowers and
animal prey.
Behavior: Their group sizes vary from 4-35 individuals, and there are
usually nearly twice as many males in the troop than females. The troop
may split into smaller groups if resources are scarce. They are diurnal and
arboreal. They move through the forest quadrupedally or by suspending
themselves. Spider monkeys are also capable of moving bipedally across
branches.
Reproduction: After a gestation period of 210-225 days, females give birth
to one infant
Cotton-top Tamarin
Size: Head and body 20-29cm, tail 31-42cm long, 350-450g.
Lifespan: More than 10 years in the wild.
Babies: Usually twins, but can range from 1-4. Breeding season in Jan-Feb.
Gestation: 140-150 days, females mature in 18 months, males in 2 years.
Social life: Average group size 3-9, mated pair or several males and one female.
Highly territorial.
Distribution: South America: only in northwestern Colombia.
Habitat: Rainforests, usually in the lower canopy, seldom higher than 25-30m.
Also in open woodlands and secondary forests.
Classification: Family Callitrichidae which has 12 species
Fruit-gums: Like other tamarins, the Cotton Top Tamarin eats sap, gum as well
as fruits, nuts and nectar. They occasionally hunt and eat insects (crickets, cockroaches, stick insects, caterpillars,
ants, beetles) and other small reptiles, frogs and rodents. They even pounce on birds, killing then plucking out the
feathers before they eat the flesh. It gets most of its water from its food, and prefers to lick rain or dew than to
risk going to the ground. They also drink from small pools of water, e.g., in bromeliads, by dipping their hands.
They are active during the early morning and sleep at night in the broad forks of a particular sleeping tree.
They jump very well and can cover more than 3m in a single bound! Their grip is improved by their sharp claws
on their hands and feet. In fact, their scientific name 'oedipus' means 'swollen footed' and refers to their long
clawed hands and feet.
A cloud of Cotton-tops*: They live in groups usually a mated pair and their offspring, although sometimes there
can be several adult males with one female, or a mated pair their offspring and several other unrelated but
subordinate adults. Groups average 3-9 but can be as large as 19. Larger groups may break up into smaller
subgroups when foraging. In the wild, the groups are highly territorial with well defined boundaries. In captivity,
females are more aggressive and territorial, fights between females can lead to death. The male has a courtship
display where he dances around her and shows off his mane while standing upright. The female, however, may
mate with more than one male. Like other tamarins, twins are usually born and the father is actively involved in
caring for them. He helps during the birth, to receive and wash the newborns. The babies can move on their own
in 18-24 days although the father will carry them until they are about 3 months, passing them to the mother only
for nursing. They are weaned in 8-10 weeks.
Gibbon
Lar/White-handed Gibbon (Hylobates lar)
Size: Head and body 44-63cm tall, 4-8kgs. In some species of gibbons the males
and females are differently coloured.
Lifespan: 25 years in the wild, 34 years in captivity.
Babies: One young, occasionally twins. Gestation 230-235 days, no specific breeding season, maturity at 7 years.
Females give birth once every 2-2.5 years.
Best brachiators: Gibbons and Siamang live in the canopy and rarely descend to the ground. Because they never
had to battle with large predators or compete with other apes on the ground, they remained small and agile. Their
arms are the most exaggerated, and relatively the longest of all primates. These end in long, slender hands that make
superb hooks for swinging on branches; the thumb is attached to the wrist instead of the palm. The siamang's arms,
compared to the length of its legs, are even longer than those of the gibbons.
Nomascus: Crested gibbon (H. concolor) found in southeastern China and Indochina (131,000)
left in the wild. Symphalangus: Siamang (H. syndactylus) found in Malaysia and Sumatra.
(167,000). Bunopithecus: White-browed gibbon (H. hoolock) found in India, Bangladesh,
Myanmar and Yunnan (China) (170,000).
Hylobates: Kloss' gibbon (H. klossii) on Mentawai islands off Western Sumatra (84,000);
White-handed/Lar gibbon (H. lar) in Myanmar, Thailand, Malaysia and northern Sumatra
(250,000); Capped/Pileated gibbon (H. pileatus) in southeastern Thailand and Cambodia
(33,600); Gray/Mueller's gibbon (H. muelleri) in Borneo (1.8 million); Silvery/Moloch gibbon
(H. moloch) in Java, (20,000); Dark-handed/Agile gibbon (H. agilis) in Thailand, Malaysia,
Sumatra and southwestern Borneo (744,000). The last four are considered by some to be subspecies of the Lar
gibbon.
What are the differences between gibbons and siamang? Siamang are usually found in the lower canopy and
eat more leaves (50% of their diet) than fruits (40%). The other gibbons tend to be found higher up in the canopy,
travel further each day and eat more fruits than leaves. Gibbons prefer ripe, pulpy fruit; figs being their favourite.
They will leave unripe fruit on the tree to eat it another day. They also get proteins by ocassionally eating insects,
They investigate leaves for such juicy titbits. They may also eat bird eggs.
Social life: All gibbons and siamang are monogamous, and their social group is based on a mated pair and
their offspring, averaging 3-4 members. A family may have up to 3-4 juveniles aged 2-3 years apart; siamang
have smaller groups than other gibbons. All lesser apes strongly defend a small, stable territory, which usually
comprises about 75% of the home range. The siamang are particularly cohesive and members seldom forage more
than 8m apart. Lesser apes rarely fight to defend their territory, relying instead on a whole host of theatrics. This
includes acrobatic displays, branch breaking and chasing accompanied by loud calls. Groups constantly call out
to help space themselves out in the dense canopy and avoid accidental meetings. Siamang call out about 30% of
the day and other gibbons 80-90% of the day! Their calls can carry for several kilometres.
A mated pair produces an offspring once every 2-3 years. Newborns are sparsely furred and
the mother cuddles it constantly for warmth. Many gibbon species have babies which are
almost white as newborns and take on adult colours only at 2-4 years, usually the females
changing colour. Both parents play an active role in bringing up baby. During the first year,
the mother looks after and feeds the baby. The baby clings tight to her, even as she brachiates
through the trees, gripping her around the waist, like a belt. In the Siamang, the father takes
over when the youngster turns 2 years old. He teaches it how to walk, swing through trees and
behave in the social group. But it is the mother that teaches it what to eat. A juvenile stays
within the family group until it reaches maturity at 6-8 years.
As they near adulthood, the subadults usually leave the group because of the urge to find a
mate, and sometimes because they are chased out by their parent of the same gender.
Subadults without mates roam alone and don't have a territory. They may spend several years
searching for a mate. In contrast, Kloss gibbon parents have been observed helping their
subadult offspring gain territories by bringing them to an unoccupied part of the forest or forcing out resident
gibbons.
Lion-tailed Macaque
Size: Body length 46-61cm, males 9-11kg, females 7-8 kgs.
Lifespan: 15-20 years in the wild, 30 or more years in captivity.
Babies: One young born. Gestation 162-186 days. No specific breeding
season. Females mature at 5 years, males at 8 years.
Social life: Average 10-20, but can range from 4-34. Females usually
outnumber males, usually 1 male but can be as many as 3. Females form
stable core, males migrate.
Distribution: Only in India. Confined to a long, narrow band of
rainforests and monsoon forest in the Western Ghats (mountains) of
Southern India, measuring about 850 km in length and about 30 km wide
at its maximum width.
Habitat: Primary forests.
Classification: Family Cercopithecidae, subfamily cercopithecinae,
genus macaca, silenus-sylvanus subgroup.
Small forest tree dwellers: Lion-tails are among the smallest macaques, the most arboreal (tree dwelling) and
the only macaques to live only in dense rainforests.
Unlike any other macaque, they have a magnificent ruff or mane of golden-grey fur surrounding their all-black
faces. The prominent mane occurs in both genders and begins growing in at about 3 months of age. They have a
black body and a conspicuous long black tail with a slight tuft of hair on the tip. Face is bare and black in adults,
bright pink in the newborn. Males have projecting canines.
Lion-tail lunches: Lion-tails eat mainly fruit and thus spend 90-99% of their time in the trees. They forage
mainly at the canopy top, but they do search every level of the forest. They also eat seeds, young leaves, stems,
flowers, buds. On the ground they eat reeds, grasses, sedges. They even eat fungi by picking them off dead wood
and foliage. They forage for insects under bark and by breaking dead branches. They also eat lizards, tree-frogs,
snails and the babies of giant squirrel. Lion-tails have been seen throwing large leaves over stinging caterpillars
before grasping them with their hands. Only males, with their large canines, can open the tough skin of the durian
fruit. Although there are no records of tool use in the wild, in captivity, some lion-tails have used tools to extract
honey from a simulated termite mound.
Lion-tails rarely come down to the ground, and carefully inspect the surroundings for a long time before doing so.
They are nervous when foraging on the forest floor, and quickly jump back into the trees at the slightest alarm.
Lion-tails have cheek pouches which they quickly stuff as they forage for food in dangerous places. After they
retreat to safety, they leisurely retrieve and eat their finds. They sometimes lick dew off leaves to get water.
Although they rarely come to the ground, they are good swimmers. They begin their day feeding at the food
source closest to their sleeping tree and feed continuously until dusk, following a route that covers the major
fruiting trees. At night, they huddle into a sleeping cluster high in the canopy.
Mating and babies: There is no specific breeding season, although births usually peak at the wet season and
when food is plentiful. Lion-tailed babies have a soft black coat which changes to the adult coat in about 2
months. The mother carries the baby on her abdomen.
Social life: A lion-tailed troop is small compared to other
macaques, containing about 10-20 members, but can range from 434. The group usually consists of one adult male, several females
and juveniles, although some groups can have as many as 3 males.
Adult females outnumber adult males by about 3 to 1. Motherdaughter bonds last a lifetime and females usually remain in the
group they were born in. Males leave just before they reach
adolescence to live in bachelor groups.
Mandrill
Size: Head and body 61-76cm, tail vestigial 5-7cm. Male average 25 kg, female 11.5kg.
Mandrill males can reach 54 kg.
Lifespan: Average 20 years in the wild, 46 years in captivity.
Babies: One young, twins rare. Gestation 168-178 days, maturity at 4 years.
Social life: Harems of 1 male and 5-10 females. 6-7 harems may combine to form troops
of up to 200.
Distribution: Africa. The Mandrill is more widely distributed in Western Central Africa:
Cameroon, Gabon and the Congo. The drill is only found in Cameroon, north of the
Sanaga River and on the coastal island of Fernando Poo.
Habitat: Prefer dense rainforests near rivers, but are occasionally seen in young
secondary growths. They avoid open areas.
Classification: Family Cercopithecidae, subfamily Cercopithecinae, genus Mandrillus.
There are 2 species: the Drill (M. leucophaeus) and Mandrill (M. sphinx). Some
categorised them as baboons in the genus Papio.
Colourful nose job: The Mandrill (right) is the most colourful mammal and is more
colourful than the drill (left). Both have colourful rear ends in hues from deep scarlet, reds
and pinks to blue and a delicate lilac.
In the male drill, the face and muzzle are black, with red bands on the lower lip.
The male mandrill goes one further and replicates his red and lilac genitals on his face. He has a bright red nose with
bright blue bony ridges on either side. This mimics a snarl and the brightness and size of these ridges indicates the
male's age and condition. The whole is framed with bright orange chin and side-whiskers. His colours brighten when
he is excited: becoming bluer on his rump and chest, and red dots may appear on wrist and ankles! The female has
smaller nose ridges and a grey-black face.
Why the colourful face? Males usually make up only 7% of the population, suggesting
fierce competition among the males for breeding positions. In this competition, males gain
advantage in prominently advertising his social position and readiness to mate. This may
also explain why males are more than twice the size of females. Males also have larger
canines. The males only colour up when they reach maturity.
Mandrill munchies: They prefer fruit and only turn to other vegetation outside the
fruiting season. They also eat insects, snails, and small reptiles and mammals. Unusual
prey include the occasional snake, sea turtle eggs and crabs. They forage on the ground by lifting stones and
sifting through vegetation. They have dextrous hands with opposable thumbs and can dig, sort and prepare their
food. The heavy adult males of both species are mainly terrestrial, but females and juveniles may climb short
trees to feed. Mandrills have been observed to hunt and kill larger mammals like duikers, hunting in groups.
Large groups of mandrills will converge on a fruiting tree. Unfortunately, they also raid agricultural crops such as
cassava and oil palms.
They move on all fours when foraging. They are active during the day, starting off at dawn. They may rest during
the day in between foraging sprees. Although they forage on the ground, all climb trees for
safety when threatened by predators, and sleep in trees at night.
A parade of drills and mandrills*: Mandrills and drills live in harems which average 2025, with one male and 5-10 females, the rest being juveniles. They break up into harems to
forage during the peak of the fruiting season. When this ends and they are forced to turn to
less nutritious but widely available food, 6-7 harems may join up to form larger feeding
groups of 200-600. Small groups are quieter, while larger bands are very noisy. The
dominant male decides where the group should forage, and directs them from behind. But if
there is danger, he moves to the front. Some harems may include 2 or more subordinate
males. These are duller in colour and are slimmer. The presence of the dominant appears to suppress the maturity of
sons. Males rarely live alone, these are usually older individuals, probably ousted from their harems.
Mandrill talk: Drills are noisy, regularly grunting and screaming. Group members keep in contact with each other
while foraging through loud conversations of grunting and crowing calls. They also alert each other of predators. A
drill male's threat gesture is impressive including abruptly thrusting their head forwards, retracting their eyelids,
puckering up their lips and raising the crest of fur on their heads. Both drill and mandrill males have chest glands
which they regularly rub branches and tree trunks with. This scent helps to maintain the dominant male's aura.
Mating and babies: When the female is ready to mate, a marked swelling appears around her tail. The dominant
male is the most likely to mate with her. Mandrill babies have a black coat and pink skin for the first 2 months.
Pygmy Marmoset
Size: Head and body: 12-15cm, tail 17-23cm, 107-141g.
Lifespan: 5-8 years in the wild.
Babies: Twins. Gestation 136 days, no specific breeding season. Maturity at 2 years.
Social life: 4-15 cantered on a mated pair, led by the dominant female.
Distribution: Only in a small area of South America: the upper reaches of the
Amazon River in Ecuador, Colombia, Peru and Brazil.
Habitat: In dense impenetrable vegetation at the edges of rainforest near clearings
or along rivers, or in secondary forests.
Classification: Family Callitrichidae. It is the only species in the genus.
Mini-marmoset: Pygmy Marmosets are the smallest New World primate. Although
they also eat fruit and insects, they spend most of their time gouging trees for sweet and high-protein sap, creating
literally thousands of tiny holes. Pygmies have specialised lower canines to make these holes. Larger tamarins
who don't have the teeth to do so may steal sap from the Pygmy marmoset's holes. Pygmy marmosets prefer
secondary growths near streams. The thick vegetation gives them cover from predators, and are crawling with
insects and other food. They may also be found at the top of the canopy, unlike larger marmosets which stay
lower and away from birds of prey. Pygmies may also forage on the forest floor. They also cleverly pick off
insects that flee from a column of marauding army ants.
Pygmy marmosets are nervous creatures, and dart quickly around in the dense undergrowth using their powerful
long hind legs to make leaps many times their body length. Pygmy marmosets may occur in quite high densities
of more than 100 per square mile.
Social life: Highly social, they live in groups of 4-15, usually a mated pair and their offspring up to four
generations. Like other marmosets, one female is dominant. Only she breeds, the father and the rest of the family
doing most of the baby-sitting. They sleep together in a huddle. Their territory centres on their sap producing tree.
They mark their territorial boundaries with scent. They communicate with high-pitched sounds, many of which
are beyond the hearing range of humans. These include a long-distance trill and a high sharp warning whistle.
During threat displays, they click and fluff up the fur on their rear ends.
Babies: Usually twins are born. Sometimes two litters of twins a year. The newborn can be as much as a quarter
of the mother's weight!!
Ring-tailed Lemur
Size: Head and body 38-45cm, tail 56-62cm. 2.3-3.5kg. Scent glands on feet,
backside, wrists, and chest. Only males have scent glands on the inside upper
arm, and a horny spur over their wrist glands.
Lifespan: 18-27 years in the wild, 14 years in captivity.
Babies: Usually 1 baby, twins when food is plentiful, once a year, births
mainly in August. Gestation 136 days, weaned at 3.5-5 months. Females
mature at 1.5 years, males at 2.5 years, but usually don't mate before they are 3
years old.
Social life: Groups of 2-5 as many as 8-16. Females dominate males. The
dominant female leads the group of many males and males.
Distribution: Only in Madagascar, southern and southwestern end of the
island.
Habitat: Rocky, scrubby areas, spiny desert, dry and gallery forests. It ranges
further into the interior highlands than any other lemur. Duke Primate Centre
has a map of their distribution.
Classification: Family Lemuridae. The Ring-tail is the best known and best
studied of all lemurs. Although somewhat still in dispute, since 1988, the Ringtail is the only member of the Lemur genus, because of its unique scent glands on the wrist and inside of the
upper arms.
Devour-Ring: Ring-tails eat mainly fruits (70%), mainly wild figs and bananas. Their lower teeth form a comb
that is useful in scooping out soft fruit. They also eat a lot of leaves (25%). This is supplemented with flowers,
bark and sap. Occasionally, they indulge in insects and small vertebrates. They regularly forage on the ground for
tamarind fruit or grasses and herbs.
Ringleader: The females are extremely dominant and one usually dominates the troop of adult males and
females. Reports of group size range from 2-5 to 8-16. Females remain in the troop that they are born in, while
males usually leave. Sometimes, males migrate from troop to troop during the mating season. Females prefer to
breed with new troop members. Males and females have their own hierarchy. Hierarchy within the group is not
stable and is not transitive, i.e., if A is dominant to B and B is dominant to C, it does not mean that A is dominant
to C. A daughter is never dominant to her mother.
Ring-tails are territorial but tolerate some overlap with other groups. The females are more territorial, especially
during the breeding season. But males also actively maintain the territory with scent marking and calls. Territorial
disputes are usually settled by yelling and screaming and rarely involves physical fighting. Their home range is
usually larger than most lemurs (6-23ha) and they can travel up to 1km a day searching for food. They scent mark
their boundaries with urine and their scent glands. The males have fingernail-like spurs on their wrists which they
rub on the inner arm glands (brachial gland) before scratch-marking branches, with an audible "click"!
Ringlets: Like most lemurs, Ring-tails have only one baby, although twins are common when food is plentiful.
Newborns are not blind or naked but still quite helpless (they have blue eyes which turn golden as they grow up).
The mother carries her baby in her mouth until it can hold on to her fur by itself. When it's small, it clings onto
the mother's tummy. About 2 weeks later, it rides on her back. It takes its first steps away from mother at about 1
month, and is not independent until about 6 months. Infant mortality is high and only about 40% reach maturity.
Mothers may suckle young other than their own, and orphans from other groups are sometimes adopted.
Sumatran Orangutan
Size: male 1.4m 50-90kgs, female 1.2m 30-50kgs. Males can be twice as big as
females.
Lifespan: Average 35 years in the wild, 50 years in captivity.
Babies: One young born, twins are rare, gestation 260-270 days, no specific breeding
season, female does not mate until her last baby is 3 years old. Females mature at at 6-8
years, males at 10-14 years.
Distribution: Only in Kalimantan and Sabah on Borneo (P. p. pygmacus) and in
Sumatra (P. p. abchi)
Habitat: Relying on fruiting trees, they are found in dense primary rainforests,
mangroves, swamps, to deciduous forests and mountain forests up to 1,500m.
Sumatran Orang
Classification: The only species in the family Pongidae, with 2 subspecies. Fossils
suggest that a giant race of Orangs existed half a million years ago.
What is the difference between the orangs from Sumatra and those from Borneo?
The physical differences appear superficial, confused further by individual variations
within each group. Although Orangs ranged throughout Southeast Asia even to
Indochina in the distant past, the Sumatran and Bornean Orangs have been separated for
more than 1 million years. But in zoos, hybrids have been born as the two are kept
together in captivity.
Sumatran orang-utans have a long and narrow face, are lighter in colour and have
thicker longer hair than those from Borneo, who have a noticeably round face. The
Sumatrans live at higher and therefore colder altitudes, so their thicker coats may be a
local adaptation to the cooler climate.
The cheek pads of a male's face is very different between the 2 islands. In Bornean
orang-utans, the flanges start to appear when the male is about 8 years old and are fully
Bornean Orang
formed by the time he reaches 15. They grow outwards and forwards from the skull,
giving a concave shape to the face. Sumatran males develop their cheeks at around 10
years of age and do not stop until they are 20. Their flanges grow sideways, giving them a massive flat-faced
look. These cheek pads are made up mostly of fat.
The Sumatran males also grow long beards when they reach adulthood. Sub-adult males, though able to breed,
may not develop their cheek pads until they are 15-19 years old. And since females are attracted to cheek pads,
they often can't breed until then.
Mating: There is no distinct breeding season as food is available all year round. It is the female that chooses her
mate, although "rapes" sometimes occur. When she is ready to mate, the female listens out for the males by the
loud calls that they make and makes her way to one of them. She may then spend several days with him while she
is in season. Females are usually not attracted to males until the males develop their cheek pads. But males are
also interested the females that they come across. Because females do not show their breeding status with an
external swelling like other primates, males give passing females a close and very personal inspection. If she is
not in season, they go quickly back to the more important business of eating. If she is, he will hang around her for
a few days until she is no longer in heat. Males may compete for females.
Babies: Orang-utans have one of the most prolonged development of any mammal. A newborn Orang weighs 2kg
and remains totally dependent on mum for the first 18 months. Like human children, Orang babies have to be
taught everything that they need to know to survive. And since males have nothing to do the the female after
mating, the mother is the main teacher. The mother even feeds her baby pre-chewed food until it can eat on its
own. The baby clings to the mother's tummy until it is nearly 1 year old, and continues to ride on mum until it is
2.5 years old. A female adult usually establishes a territory near her mother often overlapping with hers. A male
will travel far to establish a separate territory.
Orangs have a very low reproductive rate: A female usually has her first infant at 12-15 years old and give
birth every 3-8 years after that. She will only mate again when her last baby is 3 years old. Even so, her latest
offspring may still stay with her after her next baby is born, leaving her only when it is 7-10 years old. A male is
usually only able to breed successfully at 15-20, when they are large enough to compete with rival males, and
develop those cheek that females so adore. Thus it is difficult for Orang-utan populations to recover quickly.
Western Lowland Gorilla
Size: Male 1.7-1.8m 140-275 kgs, female 1.4-1.5m 70-140 kgs.
Lifespan: 30 years in the wild, 50 years in captivity.
Babies: One young, twins are rare. Gestation 251-295 days, no specific breeding
season. Females mature in 6-7 years, males in 7-8 years.
Distribution: Only in Africa (see classification for distribution of the
subspecies)
Habitat: only in dense primary rainforests, although the mountain gorillas are
found in mountain forests at 1,500-3,5000m and bamboo forests at 2,5003,000m.
Classification: Family Hominidae. There is only one species with 3
subspecies/races:
The eastern gorillas (G. g. graueri): They are the largest gorillas in the world and therefore the largest primates.
Compared to the other subspecies, they have very short, black fur, and narrower longer faces and larger teeth and
jaws. There are about 4,000-8,000 left in isolated rainforest patches of eastern Zaire, Rwanda and Uganda. Some
live in mountain forests from 2,00-2,500m.
The mountain gorilla (G. g. beringei) are the most endangered with only 450 in the Virunga range of extinct
volcanoes that straddles the borders of Zaire, Rwanda and Uganda. They live in could forests from 2,700-3,000m.
They look similar to the eastern lowland, and are kept apart from them by the Zaire River.
They have the longest silkier fur, especially on the arm, and the broadest faces, most
massive jaws and shortest forearms. They also have broader chests, wider feet and hand.
The western gorilla (G. g. gorilla) has the widest distribution , is the smallest and most
abundant subspecies (40,000 in the wild). They are found in a small pocket in eastern
Nigeria but mainly from Cameroon to Gabon and into Congo. Unlike the other 2 species, its
nose has a continuous, heart-shaped ridge all round the nostrils (in the others the ridge does
not continue below the nostrils). And the male has a chestnut hairpiece.
Gorilla food: Gorillas are almost entirely vegetarian. They eat many different plants and
various parts of these plants: leaves, stem, bark, roots, fruits. They use their hands to pluck
and prepare their food, e.g., peeling stems. In the wild where the available plant foods are
extremely diverse, they have never been seen eating meat. They by-pass eggs, helpless baby
birds and honey of stingless bees. But where the vegetarian diet is simpler, grubs may be included, perhaps to
offset vitamin deficiencies. In other places, they were observed breaking into termite nests to eat the insects. But
some individuals have learnt to do so in captivity. They spend only about a third of the day feeding and about
40% of the time just resting or sunning.
They apparently get their moisture from their diet of greenery and fruit and rarely drink water in the wild. But
when they do so, they soak the fur on the back of their hands in the water, then suck the water out.
These large creatures are entirely terrestrial but can climb well. They have been seen feeding in trees at 40m
above the ground. Large males weighing 200kg regularly climb up to 20m. On the ground, they walk on all fours,
on their knuckles (knuckle-walking). They sometimes walk upright on two legs but only for short distances of
less than 20m. They don't seem to be able to swim and are reluctant even to wade across shallow water.
Gorillas don't forage aimlessly and follow a migration route based on food availability. They forage in the
daytime, spending about 45% of the time feeding. At night, they sleep in crude platform nests, each in its own
nest. They make a new nest every night, taking less than 5 minutes to make one. They sometimes rest in such
platforms in the daytime as well. In some areas, 90% of the nests are on the ground, but in others they are made
in trees, probably because there is no material for them on the ground. Of course, the heaviest gorillas usually
have no choice but to bed down on the ground!
Social life: Gorillas live in extended family groups, which average 5-10 but ranges from 2 to 32. The fully mature
male has a light 'saddle' of nearly white fur that runs down his back, side and flank; and is hence called a
silverback. A group generally comprises 1-2 silverbacks, 6 females and several juveniles and infants. Among the
males, there is a clear hierarchy based on size and only the dominant silverback male breeds. He leads his family
group and decides where they feed and sleep. When relaxed, the leading silverback is the centre of attraction for
the females and the young - it is almost invariably they who move to sit by him, or to follow him, not vice versa.
Females are strongly bonded to the male and not to each other. The females are often "acquired" by the male one
at a time, by luring or abducting them from their families as adolescents. Females are ranked by the time they
were "acquired", highest to the first female acquired. Unlike most other primates, each gorilla takes care of its
own toilet routine; mutual grooming is quite rare among the gorillas. However, some suggest that the lack of
grooming is because gorillas have a more stable social life with no aggression among group members. Thus, the
need for regular mutual assurance is less important than in more volatile species.
Babies: A young gorilla stays with its parents for up to 3 years. Although it is weaned in 8 months, it continues to
suckle for another year. It will sleep in mum's nest up till age 3, but will start experimenting with nest building
from an early age.
The gorilla is essentially a peace-loving creature that would rather retreat than fight except in circumstances when
its life is threatened and retreat is impossible. Gorilla groups have home ranges of anything from 4 to more than
30 sq. km. The area that is most used by each group tends to be fairly exclusive but there is no systematic
territorial defence such as occurs among chimpanzees for example. Gorillas regularly cross the paths of other
groups in their daily wanderings, and trouble is averted through the noisy rituals that keep the groups apart.
Gorilla talk: Gorillas make 16-22 different calls. Some are loud and can be heard up to 1km away, helping to
keep the groups spaced apart. When a male gorilla meets a strange male, he will mount an elaborate threat
display. It begins with hoots as he brings himself to a frenzy and raises himself to his full height, tearing at
vegetation and pounding his chest with his cupped hands. It culminates in an ear-splitting roar. He then takes a
few steps towards the intruder. If this fails, he goes into a full charge, screaming and waving his arms. But he
usually stops short of actual contact, and thrusts his face staring nose-to-nose with the intruder until one or the
other backs down and stalks off.