The western lowland gorilla (Gorilla gorilla gorilla)
The western lowland gorilla (Gorilla gorilla gorilla) is one of two Critically Endangered subspecies of the western gorilla (Gorilla gorilla) that lives in montane, primary and secondary forest and lowland swampland in central Africa in Angola, Cameroon, Central African Republic, Republic of the Congo, Democratic Republic of the Congo, Equatorial Guinea and Gabon. It is the nominate subspecies of the western gorilla, and the smallest of the four gorilla subspecies.
The western lowland gorilla is the only subspecies kept in zoos with the exception of Amahoro, a female eastern lowland gorilla at Antwerp Zoo, and a few mountain gorillas kept captive in the Democratic Republic of the Congo.
Description
The western lowland gorilla is the smallest subspecies of gorilla but still has exceptional size and strength. This species of gorillas exhibits pronounced sexual dimorphism. They possess no tails and have jet black skin along with coarse black hair that covers their entire body except for the face, ears, hands and feet. The hair on the back and rump of males takes on a grey coloration and is also lost as they get older. This coloration is the reason why older males are known as "silverbacks". Their hands are proportionately large with nails on all digits (similar to those of humans) and very large thumbs. They have short muzzles, prominent brow ridges, large nostrils and small eyes and ears. Other features are large muscles in the jaw region along with broad and strong teeth. Among these teeth are strong sets of frontal canines and large molars in the back of the mouth for grinding fruits and vegetables.
A male standing erect can be up to 1.8 m (5 ft 11 in) tall and weigh up to 270 kg (600 lb). Males have an average weight of 140 kg (310 lb), females of 90 kg (200 lb). Males in captivity, however, are noted to be capable of reaching weights up to 275 kg (606 lb). Males stand upright at 1.67 m (5 ft 6 in), females at 1.5 m (4 ft 11 in). Zoo owner John Aspinall claimed a silverback gorilla in his prime has the physical strength of seven or eight Olympic weightlifters, but this claim is unverified. Western gorillas frequently stand upright, but walk in a hunched, quadrupedal fashion, with hands curled and knuckles touching the ground. This style of movement requires long arms; indeed, the arm span of western gorillas is greater than their standing height.
Albinism
The only known albino gorilla – named Snowflake – was a wild-born western lowland gorilla originally from Equatorial Guinea. Snowflake, a male gorilla, was taken from the wild and brought to the Barcelona Zoo in 1966 at a very young age. He presented the typical traits and characteristics of albinism seen in humans, including white hair, pinkish skin, light colored eyes, reduced visual perception and photophobia, and was diagnosed with non-syndromic albinism. The genetic variant for Snowflake’s albinism was identified by the scientists as a non-synonymous single nucleotide polymorphism located in a transmembrane region of SLC45A2. This transporter is also known to be involved in oculocutaneous albinism type 4 in humans. As it is a recessive allele, and his parents were an uncle and niece who were both carriers, this revealed the first evidence of inbreeding in western lowland gorillas.
Habitat
Western lowland gorillas primarily live in rainforest, swamp forest, brush, secondary vegetation, clearing and forest edges, abandoned farming fields and riverine forest. They live in primary and secondary lowland tropical forest at elevations that extend from sea level up to 1,300 m (4,300 ft). The average amount of rainfall in the areas where western lowland gorillas typically reside is about 1,500 mm (60 in) a year, with the greatest rainfall between the months of August and November. Western lowland gorillas are not typically observed in areas that are close to human settlements and villages. They have been known to avoid areas with roads and farms that show signs of human activity. These gorillas favor areas where edible plants are more copious. Swamp forest is now considered an important food source and habitat for the western lowland gorilla. These areas support the gorillas in both wet and dry seasons. The forest of the Republic of the Congo is currently considered to host the majority of the western lowland gorilla population. The isolation of the large swampy forest areas protects the gorillas.
Diet
The Western lowland gorilla is primarily herbivorous, and its main diet consists of roots, shoots, fruit, wild celery, tree bark and pulp, which are found in the thick forest of Central and West Africa. During the wet season gorillas commonly consume fruits. In the dry season, they eat less fleshy fruits, but they continue to eat other kinds of fruits. The diversity of fruits consumed was higher in a poor fruit year, when favored fruit species failed to produce large crops. They may also eat insects from time to time. The common food item which provides fibers is herbaceous stems.
Important food species have been divided into three categories: staple foods which are eaten on a daily/weekly basis throughout the year; seasonal foods which are present in the majority of resources when available; and fallback foods which are always available, but eaten only or mainly during fruit-scarce months. The adult will eat around 18 kg (40 lb) of food per day. Gorillas will climb trees up to 15 meters in height in search of food. They never completely strip vegetation from a single area, since the rapid regrowth of the vegetation allows them to stay within a reasonably confined home range for extended periods of time.
They eat a combination of fruits and foliage, providing a balance of nutrients, depending on the time of year. However, when ripe fruit is available, they tend to eat more fruit as opposed to foliage. When ripe fruit is in scarce supply, they eat leaves, herbs and bark. During the rainy months of July and August, fruit is ripe; however, in the dry seasons, ripe fruit is scarce. Gorillas choose fruit that is high in sugar for energy, as well as fiber.
Relationship with humans
The presence of western lowland gorillas has allowed the study of how gorillas compare with humans in regard to human diseases, behavior, and linguistic and psychological aspects of their lives. They are hunted illegally for their skins and meat in Africa and captured to be sold to zoos. While defended as economically profitable for restaurants and local people, such hunting contributes greatly to the endangered status of the western lowland gorilla. They are also seen as a crop pest in western Africa, because they raid plantations, and so destroy valuable crops.
