Genus and species: Nomascus leucogenys
Distribution and Habitat:
White-cheeked gibbons are found in Laos, Vietnam, and southern
China in evergreen tropical rainforests and monsoon forests.
Gibbons have a home range of about 75 to 100 acres (0.3 to
0.4 km2) and travel about one mile (1.6 km) per day through
this range. They defend approximately three-quarters of their
range as their group territory. Defense takes the form of
calls from the center of the territory, calls from the boundaries,
confrontations across the boundaries, chasing across the boundaries,
and, rarely, physical contact between males. Gibbons are arboreal
and spend most of their time in the canopy. They rarely stay
on the ground for very long. Here at the Zoo the gibbons spend
more time on the ground. You may see youngsters
wrestling in the grass.
White-cheeked gibbons are 18 to 25 inches (47 to 64 cm) tall
and weigh about 15 to 20 pounds (7 to 9 kg). Our females are
slightly heavier than males, which is not typical of gibbons in the
wild. They exhibit sex- and age-linked color dimorphism. All
infants are a beige color. By the time they are one to one and a half
years old, their coat has become black with white cheek patches.
At sexual maturity (five to seven years), males remain black and
females become a beige color again. The external genitalia
of males and females are remarkably similar, and the sex of
an individual can be hard to determine without close examination.
Both sexes have long, dagger-like canines.
Like all gibbons, white-cheeked gibbons live in small, monogamous
families composed of a mated pair and up to four offspring.
They are physically independent at about three, mature at
about six, and usually leave the family group at about eight,
though they may spend up to ten years in their family group.
Gibbons are one of the few apes where the adult female is
the dominant animal in the group. The hierarchy places her
female offspring next followed by the male offspring and finally
by the adult male.
Grooming is an important social activity between adults,
between sub-adults, and between adults and young. Infant centered
play behavior is another common social activity.
Vocalization (see gibbon communication information
) is a major
social investment. The basic pattern is an introductory sequence
where both male and female “warm up,” followed
by alternating sequences of male and female calls and of female
great calls, usually with a male coda at the end. Calls are
often accompanied by behavioral acrobatics.
Reproduction and Development:
The menstrual cycle is 28 days, and the gestation period is
seven months. White-cheeked gibbons give birth to a single
offspring every two or three years. Infants cling to their
mothers from birth. Newborns are often found clinging horizontally
across the female's abdomen. This allows the mothers to sit
with their knees up as most gibbons do. Older infants orient
vertically on the abdomen. Youngsters are weaned early in
their second year. Once the offspring reach full maturity
they usually leave the family group and search for a territory
and mate of their own.
Diet in the Wild:
White-cheeked gibbons eat mostly ripe fruits, leaves, and
a small amount of invertebrates. Fruit eating occupies about
65 percent of feeding time and young leaf eating about 35
percent of feeding time. They move and feed mainly in the
upper and middle levels of the canopy and almost never come
down to the ground. Families often feed together in the trees.