Gorillas are large, quiet, gentle apes that live in Africa. Although gorillas are frequently portrayed as aggressive, dangerous killers, they are really shy, peaceful vegetarians. Because of massive loss of habitat, these majestic primates are in great danger of going extinct.

ANATOMY Gorillas have very long arms (the arms are longer than the legs), and a short, bulky body with a wide chest.

Hair and Skin: Gorillas are covered with brownish hair on most of their body (except their fingers, palms, face, armpits, and bottoms of their feet).

The Head: Gorillas have a very large head with a bulging forehead, a crest on top (it is called the sagittal crest, and is larger on male gorillas), tiny ears, and small, dark-brown eyes. Gorillas have no tail. Adult gorillas have 32 teeth, with large molars (flat teeth used for chewing food) and large canines (pointy teeth used for biting), which are especially large in the male gorillas. Gorillas each have a unique nose print (like we have unique fingerprints).

Senses: Gorillas have senses very similar to ours, including hearing, sight (they seem to be slightly nearsighted and to have color vision), smell, taste, and touch.

Hands and Feet: Gorillas' hands are very much like ours; they have five fingers, including an opposable thumb. Their feet have five toes, including an opposable big toe. Gorillas can grasp things with both their hands and their feet.

SIZE Male gorillas are much larger than the females, and are almost twice as heavy. Adult male gorillas are called silverbacks because they have a saddle-shaped patch of silver hair on their backs after they are about 12 years of age.

DIET Gorillas are predominantly herbivores, eating mostly plant material. They forage for food in the forests during the day. They eat leaves, fruit, seeds, tree bark, plant bulbs, tender plant shoots, and flowers. They have been known to eat various parts of over 200 different plant species. Occasionally, gorillas supplement their diet with termites and ants. Gorillas rarely drink water; the water contained in their diet is apparently enough to sustain them. An average adult male eats approximately 50 pounds of food a day.

INTELLIGENCE AND LANGUAGE Gorillas are very intelligent and can learn extremely complex tasks.

Language: Some gorillas have been taught sign language by people; these gorillas learned how to form simple sentences and communicate with people.

Tools: Gorillas have never been observed using tools in the wild, although they have been taught to use them in captivity.

BEHAVIOR AND SOCIAL HABITS
Bands of Gorillas: Gorillas are shy, social animals that are active during the day (they are diurnal). They live in small groups (or bands) of 6-7 individuals, including one silverback (adult male), a few females, and their young. When the young mature, they go off and join or form another band.

Grooming: Grooming one another (cleaning the hair of another gorilla) is a major occupation among gorillas in a band. Female gorillas groom their offspring, one another, and the silverback; the silverback does not groom others.

Sleeping Nests: Each evening, gorillas construct a "nest" for the night in which they will curl up and sleep. These bowl-shaped nests are made out of leaves and other plant material. Nests are only shared by a mother and her nursing offspring. Scientists who study gorillas can easily estimate a local gorilla population by counting the number of "nests."

Aggression: Gorillas are not aggressive animals. When an intruder disturbs them, they may make a lot of noise, but they rarely confront another animal.

COMMUNICATION AND VOCALIZATION
Gorillas are generally quiet animals. They communicate with each other using many complicated sounds and gestures. Gorillas use at least 25 recognized vocalizations, including grunts, roars, growls, whines, chuckles, hooting, etc. Some gorilla gestures include chest-beating, high-pitched barks, lunging, throwing objects, staring, lip-tucking , sticking out the tongue, sideways running, slapping, rising to a two-legged stance, etc.

Communication is used to teach the young the many skills that they need to survive, and for other gorillas to communicate about food, social relationships, distress, mating, etc.

LOCOMOTION
Gorillas knuckle-walk using both their legs and their long arms (putting pressure on their knuckles, with the fingers rolled into the hand). Gorillas rarely walk using only their legs. They can climb trees, but do not do so very often. Gorillas cannot swim.

LIFE SPAN
Gorillas live about 50 years in captivity; their life span in the wild is only about 35 years (like most animals, they live much longer in captivity).

HABITAT
Gorillas are primarily terrestrial (although they lived in trees back in their evolutionary past). Gorillas live in tropical rain forests (in the forest edges and clearings), wet lowland forests, swamps, and abandoned fields.

DISTRIBUTION
The different subspecies of gorillas live in different parts of western Africa.

* Subspecies G. g. gorilla, the western lowland gorilla, is found at low altitudes in Cameroon, Central African Republic, Gabon, Congo, and Equatorial Guinea.

* Subspecies G. g. graueri,the eastern lowland gorilla, is found in eastern Zaire.

* Subspecies G. g. beringei, the mountain gorilla, is found at high altitudes (from 5,400 to 12,440 feet or 1,650 to 3,800 m) in Zaire, Rwanda, and Uganda.

REPRODUCTION AND BABY GORILLAS
Gorillas are fully grown and able to reproduce at 10-12 years old. Female gorillas are pregnant for about 8 to 9.5 months and have about 3 babies in their lifetime. Newborn gorillas weigh only about 3-4 pounds (1.4 to 1.8 kg) at birth (about half the weight of a newborn human).

Female gorillas carefully nurture their young. Baby gorillas learn to crawl at about 2 months (much earlier than humans) and can walk before they are 9 months old (earlier than most humans). They can grasp their mother's fur to ride on the mother's back at 4 months. Baby gorillas are fed mother's milk for the first 2 1/2 years of life. When they are weaned, gorillas begin to build their own sleeping nests out of vegetation (and not use their mother's nest anymore). Young gorillas stay with their mother for 3-4 years. Adult male gorillas (silverbacks) will care for weaned orphaned young gorillas.

POPULATION COUNTS
Gorilla populations are decreasing; they are in danger of extinction. Scientists estimate that there are roughly 50,000 gorillas left in the wild in Africa. Most of these are western lowland gorillas; there are only about 600 mountain gorillas and 2,500 eastern lowland gorillas. Mountain gorillas are on the verge of extinction.

THE EVOLUTION OF GORILLAS
The earliest-known primates date from about 70 million years ago (Macdonald, 1985). The greater apes (family Pongidae, gorillas, chimpanzees, bonobos, and orangutans) split off from the lesser apes (family Hylobatidae, gibbons and siamangs) 20 million years ago. The gorilla's closest relative genetically is the chimpanzee (who is also our closest relative in the animal kingdom).

CLASSIFICATION
Gorillas belong to the:
* Kingdom Animalia (all animals)
* Phylum Chordata
* Subphylum Vertebrata (animals with backbones)
* Class Mammalia (warm-blooded animals with fur and mammary glands)
* Order Primates (which is comprised of 11 families, including lemurs, monkeys, marmosets, lesser apes, great apes, and humans)
* Family Pongidae (the great apes, including gorillas, chimpanzees, bonobos, and orangutans)
* Genus Gorilla (gorillas and orangutans)
* Species gorilla
o Subspecies G. g. gorilla - the western lowland gorilla (found in Cameroon, Central African Republic, Gabon, Congo, and Equatorial Guinea)

o Subspecies G. g. graueri - the eastern lowland gorilla (found in eastern Zaire)

o Subspecies G. g. beringei - the mountain gorilla (found in Zaire, Rwanda, and Uganda)

More Information: Gorillas, the largest of the living primates, are ground-dwelling herbivores that inhabit the forests of Africa. Gorillas are divided into two species and (still under debate as of 2008) either four or five subspecies. The DNA of gorillas is 98%–99% identical to that of a human,[2] and they are the next closest living relatives to humans after the two chimpanzee species.

Gorillas live in tropical or subtropical forests. Although their range covers a small percentage of Africa, gorillas cover a wide range of elevations. The Mountain Gorilla inhabits the Albertine Rift montane cloud forests of the Virunga Volcanoes, ranging in altitude from 2225 to 4267 m (7300-14000 ft). Lowland Gorillas live in dense forests and lowland swamps and marshes as low as sea level.

Group life
A silverback is an adult male gorilla, typically more than 12 years of age and named for the distinctive patch of silver hair on his back. A silverback gorilla has large canine teeth that come with maturity. Black backs are sexually mature males of up to 11 years of age.

Silverbacks are the strong, dominant troop leaders. Each typically leads a troop (group size ranges from 5 to 30) and is in the center of the troop's attention, making all the decisions, mediating conflicts, determining the movements of the group, leading the others to feeding sites and taking responsibility for the safety and well-being of the troop. Younger males called blackbacks may serve as backup protection.

Males will slowly begin to leave their original troop when they are about 11 years old, traveling alone or with a group of other males for 2–5 years before being able to attract females to form a new group and start breeding. While infant gorillas normally stay with their mother for 3–4 years, silverbacks will care for weaned young orphans, though never to the extent of carrying the little gorillas.

If challenged by a younger or even by an outsider male, a silverback will scream, beat his chest, break branches, bare his teeth, then charge forward. Sometimes a younger male in the group can take over leadership from an old male. If the leader is killed by disease, accident, fighting or poachers, the group will split up, as the animals disperse to look for a new protective male. Very occasionally, a group might be taken over in its entirety by another male. There is a strong risk that the new male may kill the infants of the dead silverback.

Gorillas are closely related to humans and are considered highly intelligent. A few individuals in captivity, such as Koko, have been taught a subset of sign language.

Both species of gorilla are endangered, and have been subject to intense poaching for a long time. Threats to gorilla survival include habitat destruction and the bushmeat trade. In 2004 a population of several hundred gorillas in the Odzala National Park, Republic of Congo was essentially wiped out by the Ebola virus. A 2006 study published in Science concluded that more than 5,000 gorillas may have died in recent outbreaks of the Ebola virus in central Africa. The researchers indicated that in conjunction with commercial hunting of these apes creates "a recipe for rapid ecological extinction". Conservation efforts include the Great Ape Survival Project, a partnership between the United Nations Environment Programme and the United Nations Educational, Scientific and Cultural Organization, and also an international treaty, the Agreement on the Conservation of Gorillas and Their Habitats, concluded under UNEP-administered Convention on Migratory Species. The Gorilla Agreement is the first legally-binding instrument exclusively targeting Gorilla conservation and came into effect on 1 June 2008.