Gorillas are the largest of the great apes, but the western lowland gorilla is the smallest of the subspecies. Native to the Congo Basin, the western lowland gorilla is a quiet, peaceful and nonaggressive animal threatened by disease and poaching.
In 2007, the status for western gorillas was changed from endangered to critically endangered. The western lowland gorilla is the most numerous and widespread of all gorilla subspecies.
Males are much larger than females. Adult males weigh an average of 300 pounds and up to 500 pounds. They stand up to 6 feet tall. Adult females weigh from 150 to 200 pounds and stand up to 4.5 feet tall. Adult males have an arm span of 8 feet, and females have an arm span of 6.5 feet.
The gorilla’s coat color is black. Short, thin, gray-black to brown-black hair covers the entire body except the face. Western lowland gorillas may have a more brownish coloration. Older male gorillas are called “Silverbacks” because they grow grayish white hair on their shoulders and backs. They also have wider skulls with more pronounced brow ridges and smaller ears.
The duration and frequency of sexual activity in gorillas is low in comparison to other great apes. The silverback has exclusive mating rights with the adult females in his group. The reproductive success of males depends upon the maintenance of exclusive rights to adult females. The female chooses to mate with the silverback by emigrating into his family group.
Females become sexually mature between 6 and 9 years of age, usually having their first baby between ten and eleven years old. There is no set time of year for gorilla births. Western lowland gorilla gestation lasts about eight and a half months. The offspring have an instinctive grasp behavior seen in other primates, allowing them to hold onto their mothers’ chests. A
small white tuft of hair on their rump distinguishes infants up to four years old. The white patch helps the mother keep track of the infant and assists other group members in identifying the gorilla as an infant.
A female may have between three and six off-spring in her lifetime. She is reproductive throughout her lifetime and does not experience menopause. As females become sexually mature, they transfer family groups or join lone males.
Gorillas communicate using auditory signals, visual signals and odors. They are generally quiet animals but they may also scream, bark and roar. Scientists have heard up to 22 different gorilla vocalizations, each seeming to have its own meaning. Gorillas exhibit complex and dynamic relationships. They interact using grooming behaviors, although less than most other primates.