Gorillas: Physical Characteristics and Special Adaptations

Physical Characteristics and Special Adaptations

A. Size.

Adult female gorillas tend to be shorter than adult males, and weigh only half as much. Females average 1.4 m (4.6 ft) and 90 kg (198 lb.). Males average 1.7 m (5.6 ft.) and 180 kg (397 lb.).

B. Body.

1. A gorilla has a stocky build with a broad, shallow chest, a short trunk and longer arms than legs. The elongated arms indicate the gorilla's tree-dwelling ancestry even though it is now primarily terrestrial.

2. The thumb and big toe oppose the other digits, enabling gorillas to grasp and/or manipulate objects.

3. Normal locomotion is quadrupedal (using all four limbs). Gorillas knuckle-walk by curling up their fingers and walking on the soles of their feet (Schaller, 1963).

Film clip of gorilla locomotion. (470 K)

4. Bipedal (two-legged) locomotion is rare. Gorillas generally travel no farther than about 6 m (20 ft.) on two legs. The upright stance is used for chest-beating, to observe something, or to reach an object (Schaller, 1963).

5. Like all apes, gorillas do not have a tail.

6. The gorilla's pot-bellied appearance comes from an enlarged intestine needed to accomodate and digest the bulky food items on which this great ape feeds (Maple, 1982).

C. Head.

1. The head of a gorilla is massive, with a bulging forehead overhanging the eyes and a bony sagittal crest on top. The crest is especially noticeable in adult males and supports the large temporal muscles needed to grind vegetation.

2. The faces of individual gorillas vary from flat to prominent, round to oval.

3. Their nose regions are very distinctive and are used to distinguish individual animals in the field (Schaller, 1963).

4. The ears lie close to the skull.

5. The small eyes are usually dark brown.

6. Gorillas have 32 teeth. The canines are strongly developed, and the male's canines are much larger than the female's. The molars are quite large to process the amount of vegetation gorillas eat.

D. Hair.

1. Adult gorillas lack hair on the fingers, the soles of the hands and feet, and armpits. Hair is sparse on the upper chest, especially on older males.

2. The skin of a gorilla is dark and covered with black to reddish-brown hair. As the animals mature, the hair turns gray. Males acquire silver-gray saddles across their backs and upper thighs at sexual maturity, earning them the name silverback.

3. Newborns initially have pinkish-gray skin which quickly darkens. They frequently have a white rump patch until a few years old.

E. Learning capacity.

1. All great apes exhibit a capacity for complex learning. In behavioral research facilities, some gorillas have learned sign language and formed very simple sentences to communicate with people.

2. Chimpanzees have been observed creating tools from their environment and then using them to accomplish certain tasks such as probing for termites with sticks or gathering water for drinking with crumpled leaves. Young chimps learn these behaviors from watching other chimps. Gorillas have not been observed making or using tools in the wild.

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