Western Lowland Gorilla

Class: Mammal

Exhibit: PECO Primate Reserve

Status

Status
This animal is currently Critically Endangered
Endangered
Extinct in the Wild
Least Concern
Near Threatened
Vulnerable

Western Lowland Gorilla

Gorilla gorilla gorilla

Western lowland gorillas are classified as Critically Endangered by the International Union for Conservation of Nature (IUCN). Gorillas are threatened by human population growth, expansion of agriculture, logging, mining, and cattle ranching. They also are hunted for bushmeat, which is currently a major threat to their population. Recent western lowland gorilla population estimates were approximately 150,000 in the wild, mostly in the Congo and Gabon. Numbers today may be substantially lower due to hunting pressure and disease outbreaks. The other types of gorillas survive in much smaller numbers, with estimates of 8,000-17,000 for the eastern lowland gorilla, only 150-200 for the Cross River gorilla, and 600 for the mountain gorilla. The Zoo has a great partnership with GRACE, a gorilla rehabilitation center in the Congo that helps wild gorillas.

Females reach sexual maturity at about 6 years old and males at 10 years old. The dominant male usually has at least two females with whom he mates and defends. A mating season doesn’t seem to exist, with births occurring throughout the year and pregnancy lasting about 256 days with usually one single young born. In contrast with other primates, gorilla babies cannot hold to their mothers right away but only after about three months. By four months old they can walk on all fours, and by six or seven months they are climbing all over their mothers. These animals learn by experience and by reasoning; babies begin crawling at 9 weeks and walking at 30 to 40 weeks. Females will only get pregnant again after about 4 years or more, when the infant has already been weaned.

What are they like?

Physical Description: Western lowland gorillas have thick black fur and a brown patch on the top of their head. When males become mature, around 13 years, they develop a silvery color fur in their back. A gorilla's face is black with no fur, and the heads are conically elongated, particularly in adult males. Their height is about 8 feet when standing erect and about 5.5 when knuckle-walking. Males on average weigh 300-500 pounds while females average half as much as males.

Life Span: In the wild, western lowland gorillas can live up to 35 years. In zoos, gorillas can live up to 55 years.

Diet: In the wild, gorillas eat mostly fruit, leaves, and other plant parts. At the Zoo, our gorillas eat a nutritionally complete primate chow plus an assortment of fresh produce like grapes, apples, carrots, tomatoes, kale, and other lettuces.

Social Structure: Gorillas gather in groups of 3 to 21 members, usually composed of one dominant male and various females, but occasionally having 2 silverbacks, their females, and offspring.

Habitat: Western lowland gorillas inhabit dense primary rainforest, swamp forest, thicket, secondary vegetation, forest edges and clearings, riverine forests and abandoned cultivated fields within or adjacent to forest. At the Zoo, our gorilla enclosure consists of a day room connected to the Great Ape Trail with climbing towers, fire hose for swinging on, and a space where keepers can work with them. Their yard is large and grassy with a climbing tower.

Where do they live?

Western lowland gorillas are found in lowland tropical forests of Cameroon, Gabon, Equatorial Guinea, Congo, and Central African Republic.

Cameroon, Gabon, Equatorial Guinea, Congo, and Central African Republic

Did you know?

Western lowland gorillas are diurnal and live on the ground but will climb trees to forage for food, rest, and sleep. Females and young seem to climb trees more often, while males usually rest and feed on herbs on the ground.
Gorillas move through the forest on the ground by “knuckle walking,” moving on their feet and the knuckles of their hands. Some days they move less than a mile, whereas other days they move more than 8 miles.
In 1984, the Philadelphia Zoo set a longevity record for gorillas by Massa, a male, who lived 54 years. This record has only recently been broken.
The keepers trained our gorillas to help with veterinary care procedures. All of the gorillas are injection-trained to accept a needle in their shoulder. They are trained to stand up and turn around so the keepers can examine their entire bodies. Because injuries are most common on the hands, feet, head, and back, keepers have trained the gorillas to present those body parts for examination and to stick out their tongue.