ALL ABOUT GORILLAS

Gorillas are the largest species of primates alive today. They are ground-dwelling, predominantly herbivorous, and although they are frequently portrayed as aggressive, dangerous killers, they are in reality shy, peaceful vegetarians. Furthermore, because of massive loss of habitat, these majestic primates are now at huge risk of extinction!

Mountain Gorilla

Gorillas are divided into two species and then further still into four or five subspecies. The DNA of gorillas is incredibly similar to that of humans, between 95 and 99%! In fact they are our closest living relatives next to chimpanzees.

Gorilla Habitat

The Gorillas natural habitat covers the tropical and subtropical forests of Africa. Although their range covers only 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 7,200–14,100 ft. Lowland Gorillas live in dense forests and lowland swamps and marshes as low as sea level, with western lowland gorillas living in Central West African countries and eastern lowland gorillas living in the Democratic Republic of the Congo near its border with Rwanda.

Gorilla Behaviour

Gorilla family

Gorillas live in groups called troops. Each troops will tend to be made of one adult male or silverback, multiple adult females, and their offspring. However, multi-male troops also exist.

Silverbacks are typically more than 12 years of age and named for the distinctive patch of silver hair on his back, which comes with maturity. A silverback gorilla has large canine teeth that also come with maturity.

Both males and females tend to emigrate from their natal groups. Dispersal from natal troops is more common in females than males for mountain gorillas. Female mountain gorillas and western lowland gorillas also commonly transfer to a second new group.

Gorilla family

Mature males tend to also leave their groups and establish their own troops by attracting emigrating females. However, male mountain gorillas sometimes stay in their natal troop and become subordinate to the silverback. They may gain the opportunity to mate with new females or become dominant if the silverback dies. This behavior has not been observed in eastern lowland gorillas.

In a single male group, when the silverback dies, the females and their offspring disperse and find a new troop. Without a silverback to protect them, the infants will likely fall victim to infanticide, and searching out and joining a new group is likely to be a tactic against this. However, while gorilla troops usually disband after the silverback dies, female eastern lowlands gorillas and their offspring have been recorded staying together until a new silverback transfers into the group. This likely serves to decrease chance of being attacked by leopards. Although very rare, all male troops have also been recorded.

Silverback Gorillas

Male silverback gorilla

The silverback is the center of the group'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 subordinate to the silverback, known as blackbacks, may serve as backup protection. Blackbacks are males between 8 and 12 years of age and lack the silver back hair. The bond a silverback has with his females forms the core of gorilla social life. Bonds between them are maintained by grooming and close proximity. Having strong relationships with males is important for females as males give them mating opportunities and protection from predators and infanticidal outside males. However aggressive behaviors between males and females are common although they rarely lead to serious injury.

Relationships between females may vary. Maternally related females in a troop associate closely and tend to have friendly interactions. Otherwise, females usually have little friendly interactions and commonly act aggressive towards each other. Aggressive interactions between females tend to be centered around social access to males with males intervening in fights between females. Male gorillas have weak social bonds, particularly in multi-male groups with apparent dominance hierarchies and strong competition for mates. However, males in all-male groups tend to have friendly interactions and socialize through play, grooming and close proximity, and occasionally they even engage in homosexual interactions.

Gorilla Nests

Gorilla nest

Gorillas construct nests for daytime and night use. Day nests tend to be simple aggregations of branches and leaves on the ground while night nests are more elaborate constructions in trees. The nests may be 2 to 5 feet in diameter and are constructed by individuals. The young nest with the mother but construct nests after three years of age, initially close to that of their mother. Gorilla nests are distributed arbitrarily and use of tree species for site and construction appears to be opportunistic. Nest building by great apes is now considered to be not just animal architecture but as an important instance of tool use.

How do Gorillas Communicate?

Gorilla confrontation

There are now twenty-five distinct vocalizations recognized now through extensive scientific research, many of which are used primarily for group communication within dense vegetation. These sounds classified as grunts and barks are heard most frequently while traveling. They are often used to indicate the whereabouts of individual group members. They may also be used during social interactions when discipline is required. Screams and roars signal alarm or warning, and are produced most often by silverbacks.

Deep, rumbling belches suggest contentment and are heard frequently during feeding and resting periods. They are the most common form of intragroup communication. Severe aggression is rare in stable groups, but when two mountain gorilla groups meet, the two silverbacks can sometimes engage in a fight to the death, using their canines to cause deep, gaping injuries. The entire sequence has nine steps:

1. Progressively quickening hooting.
2. symbolic feeding.
3. Standing upright.
4. Throwing vegetation.
5. Chest-beating with cupped hands.
6. A single leg kick.
7. Sideways running, two-legged to four-legged.
8. Slapping and tearing vegetation.
9. thumping the ground with palms to end display.

Tool use in Gorillas

Tool use

The following observations were made by a team led by Thomas Breuer of the Wildlife Conservation Society in September 2005. Gorillas are now known to use tools in the wild. A female gorilla in the Nouabalé-Ndoki National Park in the Republic of Congo was recorded using a stick as if to gauge the depth of water whilst crossing a swamp. A second female was seen using a tree stump as a bridge and also as a support whilst fishing in the swamp. This means that all of the great apes are now known to use tools.

In September 2005, a two and a half year old gorilla in the Republic of Congo was discovered using rocks to smash open palm nuts inside a game sanctuary. While this was the first such observation for a gorilla, over 40 years previously chimpanzees had been seen using tools in the wild, famously 'fishing' for termites.

Great apes are endowed with a semi-precision grip, and certainly have been able to use both simple tools and even weapons, by improvising a club from a convenient fallen branch.

For related articles click onto the following links:
ALL ABOUT GORILLAS
CHIMPANZEE FACTS
WHAT DO GORILLAS EAT?
WHAT IS A GORILLA?