Did you know that we humans are practically gorillas? Though we are closer to chimpanzees and bonobos, we still share 98-99% of our DNA with gorillas – together with chimpanzees we diverged from gorillas about 7 million years ago. I find that astounding! Hollywood has tatooed a King Kong image of gorillas onto our brains of a buffoonish aggressive hairy beast, – like us these apes are smart. In 2005 scientists from the Wildlife Conservation Society documented the first case of tool use among gorillas – individual gorillas were using sticks to check the depth of streams before crossing them. Rubbish compared to human inventions…well, for all our intelligence how come we seem to be unable to save them?
Maybe we don’t actually need to worry you ask? The recent announcement that WCS had discovered 125,000 more gorillas than were previously known in the Republic of Congo means that they are safe no? Not at all! This announcement has confused many people as it suggests that gorillas are not endangered anymore . The truth is that Gorillas are still in bad shape. The confusion over species and subspecies, and DR Congo vs Republic of Congo …it’s brain twisting and infuriating. (I’ve been scouring the web for the original publication to understand how they came up with this figure and to understand the actual geographical distribution of this population. Anyone out there got it?)
WCS found more western lowland gorillas in the Repblic of Congo, – where does this fit into the various species and sub-species? Read on to find out.
First some background for any Gorilla newbies….
Gorillas are amazing animals. They live in tropical or subtropical forests only in Africa. Their range covers a small percentage of the continent, and a wide range of elevations. They are herbivores and spend most of their day eating fruits, leaves, and shoots. Lowland gorillas feed mainly on fruit while Mountain gorillas feed mostly on herbs, stems and roots.
Gorillas forage in early morning, rests during the late morning and around midday, and in the afternoon it forages again before resting at night. Each gorilla builds a nest from surrounding vegetation to sleep in, constructing a new one every evening. Only infants sleep in the same nest as their mothers. They leave their sleeping sites when the sun rises at around 6 am, except when it is cold and overcast; then they often stay longer in their nests.
Gorilla society comprises families of 5 to 30 individuals led by the silverback – an adult male gorilla who is typically more than 12 years of age. A silverback gorilla has large canine teeth that come with maturity.
Silverbacks are strong dominant troop leaders who make 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. Black backs are sexually mature males of up to 11 years of age.
Females start breeding at about 10 and gestation lasts 8 and a half months. They will typically have one baby every 4 years or so. Infants normally stay with their mother for 3–4 years, silverbacks care for these weaned young orphans.
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 terrifyingly towards his foe. Occasionally, a group might be taken over by another male who will kill the infants of the former silverback. Or the silverback could die and a younger male in the group can take over leadership. Often when this happens however, the group will split up, as the animals disperse to look for a new protective male.
Young adult males 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.
The different species of gorilla
There are two different species of Gorilla, Eastern gorilla (Gorilla graueri) and Western gorillas (Gorilla gorilla). These two species are geographically separated (see map below). Each of these species has two subspecies (with a possibility of a third in the eastern gorilla). The following information was compiled from Wikipedia amongst other sources.
This map approximates the disrribution of these different species and sub-species. A third subspecies of Gorilla beringei has been proposed the Bwindi population of the Mountain Gorilla, sometimes called the Bwindi Gorilla.
The Eastern Gorilla (Gorilla beringei) is the largest living primate. The species is subdivided into two subspecies. The Eastern Lowland Gorilla (G. b. graueri) is the most populous, at about 16,000 individuals. The Mountain Gorilla (G. b. beringei) has only about 700 individuals. In addition, scientists are considering elevating a portion of this population, the Bwindi gorilla population (which numbers about half of the Mountain Gorilla population) to the rank of subspecies.
The Eastern Gorilla occurs in the lowland and mountain rainforests and sub-alpine forests of eastern DR Congo, southwestern Uganda and Rwanda, within the triangle between the Lualaba River, Lake Edward and Lake Tanganyika. The Eastern Gorilla prefers forests with a substrate of dense plant material.
The Mountain Gorilla (Gorilla beringei beringei) is one of the three subspecies of the Eastern Gorilla. There are two groups. One is found in the Virunga volcanic mountains of Central Africa, within 4 national parks: Mgahinga, in south-west Uganda; Volcanoes, in north-west Rwanda; and Virunga and Kahuzi-Biéga, in the eastern Democratic Republic of Congo (DRC). The other is found in Uganda’s Bwindi Impenetrable Forest.
The Mountain Gorilla has longer and darker hair than other gorilla species, allowing it to live in hot or cold weather and travel into areas where temperatures drop below 32 degrees Fahrenheit (0 degrees Celsius). It has chosen a life on the ground more than any other non-human primate, and its feet most resemble those of humans.
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). Most are found on the slopes of three of the dormant volcanoes: Karisimbi, Mikeno, and Visoke. The vegetation is very dense at the bottom of the mountains, becoming more sparse at higher elevations, and the forests where the Mountain Gorilla lives are often cloudy, misty and cold.
The home range size (the area used by one group of gorillas during one year) is influenced by availability of food sources and usually includes several vegetation zones but preferring the Hagenia forests, where gallium vines are found year-round. All parts of this vine are consumed: leaves, stems, flowers, and berries. They also feed in the bamboo forests during the few months of the year fresh shoots are available, and it climbs into subalpine regions to eat the soft centers of giant senecio trees.
The Bwindi gorilla, a population of the Mountain Gorilla (Gorilla beringei beringei), is found in the rain forests of the Bwindi Impenetrable Forest, and comprises about half the world’s endangered population of about 600 Mountain Gorillas. The nearby Virunga Volcanoes Conservation Area, inhabited by the remaining 300 Mountain Gorillas but where no chimpanzees live, makes Bwindi the only forest in Africa in which these two great apes occur together.
The Eastern Gorilla is seldom found in zoos. The Antwerp Zoo is probably the only Western zoo that has Eastern Lowland Gorillas (two older females). Apart from a few orphans in Rwanda and Congo, the Mountain Gorilla is not held in captivity at all.
The Western Gorilla (Gorilla gorilla) is lighter in color than its Eastern cousin being brown or greyish with a reddish forehead. It also has an overhanging tip on its nose, which the Eastern Gorilla doesn’t have. Males measure 170-180cm and weigh 140-275kg. Females measure 140-150cm – in general they are more slender then the Eastern Gorilla This species is an agile climber and is more arboreal than the Eastern Gorilla. It is also more frugivorous and will eat fleshy fruits of almost 100 seasonally fruiting tree species. It is more difficult to track and study and lives in small family group compared to other gorillas, averaging 4-8 members. Wild Western Gorillas are known to use tools.
The Western Gorilla as critically endangered, the most severe denomination next to global extinction, on its 2007 Red List of Threatened Species. It is thought that the Ebola virus might be depleting Western Gorilla populations to a point where it might become impossible for them to recover. However the discovery earlier this year (mid 2008) by WCS of as many as 125,000 previously-undiscovered Western Lowland Gorillas in the Republic of Congo sometimes known as Congo-Brazaville. This finding could more than double the known population of the animals.
The Cross River Gorilla (Gorilla gorilla diehli) is a subspecies of the Western Gorilla (Gorilla gorilla) and is found on the border between Nigeria and Cameroon, in both tropical and subtropical moist broadleaf forests. The Cross River Gorilla differs from the Western Lowland Gorilla in both skull and tooth dimensions.
The Cross River Gorilla is the most endangered of all the gorillas, and is the most endangered primate. Estimates on the number of Cross River Gorillas remaining vary, with around 250 to 300 believed to be remaining in the wild, in 9 to 11 populations that are isolated by farmlands. The nearest population of Western Lowland Gorilla is some 250 km away. Both loss of habitat and the increased popularity of bushmeat have contributed heavily to the decline of this subspecies.
Does this write up and do the maps maps help to clear up who’s who and who’s where in the gorilla world?
Though millions can be generated from gorilla tourism, the areas surrounding the parks in the range of gorillas, are densely populated by very poor people. The resulting habitat loss, poaching and disease transmission all threaten wild gorillas.
In 2004 a population of several hundred gorillas in the Odzala National Park, Republic of Congo was essentially wiped out by the Ebola virus and in 2006 a 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 (GRASP), 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.
Next year we will be promoting the Convention on Migratory Species “Year of the Gorilla”. We are looking for ideas from you on how WildlifeDirect can raise more awareness, greater global involvement in gorilla conservation, and raise support for gorilla conservation projects.
Please send us your ideas and suggestions.