Western Lowland Gorilla
[Gorilla gorilla gorilla]
Western lowland gorillas are the largest of the great apes. They are sexually dimorphic with males weighing on average 374 pounds while females weighing on average 154. Adult males are called silverbacks due to a streak of silver hair that runs the length of their back from their shoulders to rump. Adult males also have a prominent sagittal crest, a large protrusion on the top of their head which is made of the skull, connective jaw muscles and fatty tissue. Gorillas have dark brown to black hair and black skin, with bare faces, hands, feet and chests.
The population is estimated at 130,000, although it is declining due to human induced habitat loss and degradation, disease (included Ebola, which killed 90-95% of the gorilla populations in two research sites within the Republic of Congo between 2002 and 2003), and hunting for the bushmeat trade.
Location: Ape Exhibits
RangeWestern lowland gorillas are found in Central African Republic, Equatorial Guinea, Gabon, Republic of Congo, Angola, Cameroon, and the Democratic Republic of Congo.
HabitatThe western lowland gorilla inhabits lowland tropical forests and swamp forests.
GestationGestation in the western lowland gorilla lasts about 8.5 months (on average 256 days).
LitterWestern lowland gorillas give birth to one offspring at a time, though rare instances of twining have occurred.
BehaviorAlthough western lowland gorillas are primarily terrestrial, like other primates they are capable of climbing. Surface locomotion is quadrupedal, with the soles of the feet and the middle phalanges of the fingers placed on the ground during locomotion. They are diurnal, with most activity taking place between 6 a.m. and 6 p.m. In the evening gorillas will make nests in the trees, nest making during the day has also been observed. Although they are nearly entirely vegetarian, they will occasionally eat insects. Gorillas are social, living in groups. When two groups meet they may ignore each other, temporarily associate, or express hostility. Groups can range from 2 to 30 in number and are commonly composed of an adult male, several adult females and their immature offspring. Males who are unable to acquire females will either form all male groups, referred to as bachelor groups, or will live alone. Gorillas communicate through a combination of vocalizations (including grunts, rumbles, whimpers, whines, and play chuckles), gestures and body posturing.
ReproductionThere is no evidence of a breeding season for western lowland gorillas, and females give birth once every 3½ to 4½ years unless the infant dies. The estrous cycle lasts 26 days, with estrus being 1 to 3 days. Physiologic sexual maturity is 8 years for females and 10 for males, although breeding does not usually occur until 10 in females and 15 in males. Females will often give birth to only 2-3 offspring in her lifetime.
Wild DietIn the wild gorillas have a diverse diet of 180 species of plant. From these plants gorillas will consume bark, fruit, flowers, herbs, leaves, pith, roots, seeds, shoots and stems. In addition wild gorillas have been observed to consume ants and termites.
Zoo DietThe gorillas’ primary diet consists of romaine lettuce, dandelion greens, endive, alfalfa hay, green beans, fruit, resistant starch, and flax seed. The gorillas also receive browse (branches from local tree species when available) and multivitamins.
- Gorilla, Western Lowland - Animal Fact Sheet
- Rivera A. (2012). Correlations between animal activity and zoo visitor attention focusing on western lowland gorillas. Unpublished manuscript. 10 pp.