Western Gorilla

Lore & Background

A formal description of the species was provided by Thomas Savage in 1847, allying the new species to an earlier description of the chimpanzee as Troglodytes gorilla in a group of eastern simians he referred to as 'orangs'. The author selected the specific epithet for the name given by Hanno to 'wild men' he had noted on the east coast of Africa, presumed by Savage to be a species of orang. Nearly all of the individuals of this taxon belong to the western lowland gorilla subspecies, whose population is approximately 276,000 individuals.

Just 250 to 300 of the only other western gorilla subspecies, the Cross River gorilla, are thought to remain. Western gorillas are generally lighter coloured than eastern gorillas. Western gorillas have black, dark grey or dark brown-grey hair with a brownish forehead. Males average 1.67 m (5.5 ft) although reaching a height up to 1.76 m (5.8 ft), with males weighing 145–191 kg (320–421 lb) and females weighing 58–72 kg (128–159 lb).

Captive western gorillas average 157 kg (346 lb) in males and 80 kg (176 lb) in females. Another source describes the weight of wild male western lowland gorillas as 146 kg (322 lb). The Cross River gorilla differs from the western lowland gorilla in both skull and tooth dimensions.

Reader's Guide

Western gorillas' diets are high in fiber, including leaves, stems, fruit, piths, flowers, bark, invertebrates, and soil. The frequency of when each of these are consumed depends on the particular western gorilla group and the season. Furthermore, different groups of western gorillas eat differing numbers and species of plants and invertebrates, suggesting they have a food culture. Fruit comprises most of the western lowland gorillas' diets when it is abundant, directly influencing their foraging and ranging patterns.

There is a correlation between the amount of time a western gorilla travels and the season in which fruits are available. Western gorillas spend more time traveling and feeding during the seasons when fruits are abundant compared to when there is less fruits available. Fruits of the genera Tetrapleura, Chrysophyllum, Dialium, and Landolphia are favoured by the western gorillas. Low-quality herbs, such as leaves and woody vegetation, are only eaten when fruit is scarce.

In the dry season from January to March, when fleshy fruits are few and far between, more fibrous vegetation such as the leaves and bark of the low-quality herbs Palisota and Aframomum are consumed. Of the invertebrates consumed by the western gorillas, termites and ants make up the majority. Caterpillars, grubs, and larvae are also consumed in rarity. Some ethnographic and pharmacological studies have suggested a possible medicinal value in particular foods consumed by the western gorilla.

The fruit and seeds of multiple Cola species are consumed. Given the low protein content, the main reason for their consumption may be the stimulating effect of the caffeine in them. Western gorillas inhabiting Gabon have been observed consuming the fruit, stems, and roots of Tabernanthe iboga, which, due to the compound ibogaine in it, acts on the central nervous system, producing hallucinogenic effects. It also has effects comparable to caffeine.

There is also evidence for medicinal value for the seed pods of Aframomum melegueta in western gorillas' diets, which seem to have some sort of cardiovascular health benefit for western lowland gorillas, and are a known part of the natural diets for many wild populations.

Did You Know?

• A female gorilla will only give birth to an offspring that survives to maturity every six to eight years.
• A study published in 2007 found several instances of gorillas throwing sticks and clumps of grass at possible threats from humans.