Gorilla

Gorilla is the largest member of the ape family and has one of the closest associations to human beings in the evolution chain. Gorilla scientific name is (genus Gorilla) and among the genus of primates chimpanzee or the bonobo, they are next in line when it comes to being closer to humans. The native natural gorilla habitat is the tropical forests of equatorial Africa. 

Types of Gorillas

According to zoologists, there are two clearly defined and recognized gorilla species and four subspecies. The two main species are the western gorilla (Gorilla gorilla) and the eastern gorilla (G. beringei). 

The western gorilla species comprises of two subspecies: the Western lowland gorilla (G. gorilla gorilla), which is found in the lowland rainforests in Cameroon to the Congo River region, and the Cross River gorilla (G. gorilla diehli), found in the forest that runs along the Cross River and separates Nigeria from Cameroon. 

The two subspecies of the Eastern gorilla (G. beringei) are the Eastern lowland gorilla, or Grauer’s gorilla (G. beringei graueri), which inhabits the eastern Democratic Republic of the Congo (Kinshasa) lowland forests, and the Mountain gorilla (G. beringei beringei), which inhabits the bamboo forests and the montane rainforests of the highland terrain north and east of Lake Kivu, close to the borders of Rwanda, Uganda, and Congo (Kinshasa).

Physical Attributes 

The gorilla is a very powerful and robust member of the simian family. One of the most distinguishing features of a gorilla is its thick and strong chest with a protruding abdomen. There is a distinct crest on the top of an adult male gorilla’s skull. The term ‘silverback’ which is often used for mature male gorillas is given because of the ‘saddle’ of silver or gray hairs on the lower part of their back. The jet black Eastern gorillas (G. beringei), display this saddle more prominently than the deep gray-brown western gorillas (G. gorilla). 

The skin and hair of a gorilla are black. The face, hands, feet, and chest of old males do not have any hair. The subspecies G. beringei beringei has longer hair than the other three gorilla subspecies. Another striking physical attribute of a gorilla is its large nostrils, distinct brow ridges, and small ears. 

Gorilla Size

The long and muscular arms of an adult gorilla are 15-20 percent longer than its bulky feet.  An adult male gorilla is heavier than a female (almost double in weight). The adult male gorilla height can go up to approx 1.7 meters (5.5 feet) and the gorilla weight (in the wild) can be around 135–220 kg (300–485 pounds).  An adult female gorilla is about 1.5 meters tall and weighs approx 70–90 kg. Gorillas can lift heavy weights- up to 815 kg (1800 pounds) which is more than three times their own weight. 

The physical attributes of gorillas in captivity differ from those exhibited by ones that live in the wild. Both male and female captive gorillas tend to put on weight and become heavier. A gorilla lifespan is about 35 years for a wild one but captive gorillas sometimes live for about 40 years or more.

Gorilla Group Dynamics

Gorillas live in family groups with 6 to 30 members making a stable group size. The leaders of a gorilla group are one or multiple male silverbacks that are related to each other. Most of the time it is a father and his sons or a group of brothers who take on the leadership role in a group. The other members in the group include infants, juveniles, females, and young adult males (also known as blackbacks). The adult females in the group are outsiders who join the group and then become a part of it while the young members are offspring of the silverbacks.

What Do Gorillas Eat?

Gorillas are vegetarians and while the diet of eastern gorillas comprises primarily of leaves, shoots, stems pith, bamboo, and stocks, the western gorillas eat more fruit. Sometimes gorillas also eat small insects like ants and snails. A full-grown adult male can eat around 50 pounds of food daily. Gorillas are not very fond of water but in areas like the Central African Republic or the Sangha-Ndoki region on the borders of Cameroon (the Republic of the Congo, Brazzaville), they venture waist-deep into swampy clearings for aquatic plants that form a part of their diet. A lot of their time is spent foraging and resting since the groups sometimes travel as far as a few hundred meters daily between their feeding times.

Behavior

The chimpanzee is the closest relative of a gorilla, which is much larger in size. While the chimpanzee is more boisterous, gorillas prefer their quiet. However, they occasionally break this quiet with their grunts, hoots, and the alarm bark. The roar of an aggressive male is terrifying and can strike fear in the heart of anyone listening. Several movies have depicted the gorilla as an aggressive and ferocious animal but studies have proven that they are shy unless they are disturbed. When unduly disturbed, gorillas tend to display some aggression. 

Gorillas lack cognitive skills in comparison to chimpanzees who display curiosity and adaptability. But what they lack in this area, they make up for in calmness and persistence. Problem-solving skills, the anticipation of experience, and a degree of memory and insight have been witnessed in captive gorillas. Gorillas can also learn sign languages from humans as easily as chimpanzees and can even recognize their image in a mirror. This behavior shows that they have a certain sense of self-awareness just like the chimpanzees and orangutans. This trait can be seen only in a few animals.

Male gorillas make a hooting sound as an alarm for all members of their group, to alert them against any danger or intrusion. Gorillas travel together in groups for months and years. Due to their large size and abundance of food in the vicinity of their habitat, they do not like spending time and energy traveling. It is also the reason why sometimes the territories of different gorilla groups overlap with each other. 

Chest-beating

The leaders of a gorilla group, the silverbacks, make aggressive displays for any intruders (other gorillas or humans)  in an attempt to protect the dependent members of the group.  This aggressive display includes vocalization, short rushed steps towards the intruder to make them withdraw, and the impressive yet daunting chest-beating. Chest beating is done both by males and females, but the sound is louder in males. It is because the air sacs in the throat and chest of a male make the sound resonate more. Chest beating is like a ritual and is coupled with sideways running, slapping, or thumping the ground and tearing at vegetation. 

Reproduction

There is no fixed breeding season for gorillas and wild females give birth once every four years. The gestation period for gorillas is around eight and a half months, and they give birth usually to a single offspring, rarely to twins. The weight of a newborn is approx 2 kg and the young ones are completely dependent on their mother for the first three months of life. During this time, the mother carries her baby in its arms. At night, the baby sleeps with the mother in the nest till it is at least 2.5 years old and during the day, rides on her back as she moves around. 

Female gorillas become reproductive at the age of 10 years and join another group or stay with a single silverback. This prevents inbreeding within the group. Males attain sexual maturity slightly earlier than the females, at the age of 9 years, but they start to reproduce only at the age of 12-15 years when they become physically mature. At this time, they gather females to start their own family group and leave the family group in which they were born. 

In order to get females in his group, sometimes a male gives a display of aggression. The young male invades another stable group and tries to “kidnap” females from this group. Sometimes infants get killed during this aggression. If the male stays back in his birth group, he becomes the second silverback. He mates with the females of the group and takes over the leadership reins when his father ages or dies.

When a silverback dies naturally or is killed by accident, disease, or by poachers, the family group may split or take on another unrelated male as their leader. This happens when there is no male descendent in the group capable of taking over the leader’s role. Sometimes, a new silverback may kill all of the infants in the group after joining. 

Gorilla Population

According to the latest gorilla information, currently, there are 1060 adult mountain gorillas in the world. Loss of their habitat to grazing, farming, and logging has abetted their near-extinction. However, ecotourism has played a critical role in the conservation of the mountain gorilla. An interest amongst tourists to see the gorillas in their natural habitat has led to an increase in their numbers.

Although the western lowland gorillas had been classified by the IUCN as critically endangered, their population estimates almost doubled in 2008 when a previously unknown population of around 100,000 gorillas was discovered. This population was found in the Lac Télé Community Reserve swamps, in the Republic of the Congo. 

Gorilla Facts

• Each group of gorillas wanders through an area of about 2–40 square km (0.77–16 square miles). Although every group has its home range, different gorilla groups sometimes share the same territory in the forest. 

• Each gorilla builds its own sleeping nest either in the trees or on the ground at dusk, using bent foliage and branches. They build a new crude nest every night. 

• Gorillas are diurnal( active during the day) and prefer to be primarily terrestrial. They usually walk about on all four limbs with the knuckles of their hands supporting part of the gorilla weight. This mode of walking is called knuckle-walking and is also seen in chimpanzees. 

• When a gorilla wants to put on a show ( a display of strength or size sometimes), it stands erect. 

• Young gorillas and females do more climbing than the males they are lighter in weight than the males and can climb without breaking the vegetation.

Fun Trivia about Gorilla

• There is a 98% match between the Human and Gorilla DNA however, gorillas do not possess the level of immunity that humans have

• They can eat all day long

• A gorilla can make 16 different types of calls when they are curious or alarmed

• The ‘belch vocalization’ call is a sign of contentment while foraging and also a contact call. They make a low grumbling sound to locate each other when travelling or foraging

• 8-12-year-old males are called ‘blackbacks’

• A gorilla named Koko had mastered more than 1000 signs