GO UP

What are the gorillas

What are the gorillas?

Gorillas are ground-dwelling, mostly herbivorous apes that live in the forests of central Sub-Saharan Africa. The Gorillas are divided into two species: the eastern gorillas and the western gorillas (both are seriously endangered). They are the largest living primates. The DNA of gorillas is highly similar to that of humans, from 95–99% depending on what is counted, and they are the next closest living relatives to humans after the chimpanzees and bonobos.

Gorillas’ natural habitats cover tropical or subtropical forests in Sub-Saharan Africa. Although their range covers 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 2,200–4,300 meters (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.

 

The Eastern gorillas

The eastern gorilla (Gorilla beringei) is a critically endangered species of the Gorilla and the largest living primate. At present, the species is subdivided into two subspecies. Grauer’s gorilla, formerly known as the eastern lowland gorilla is more populous, at about 3,800 individuals mentioned to be in the eastern Democratic Republic of Congo and the mountain gorilla has only about 880 individuals. The International Union for the Conservation of Nature mentioned illegal hunting in its assessment of threats to the species. At the present day the Eastern Mountain gorilla found in volcanic slopes of Rwanda, Uganda and eastern Democratic Republic of Congo.

Grauer’s gorillas and mountain gorillas were previously thought to be two of the three subspecies of one single species, the gorilla (Gorilla gorilla). However, genetic research has shown that the two eastern subspecies are far more closely related than the western subspecies: the western lowland gorilla (G. gorilla gorilla), which justified the separate classification. The two eastern subspecies are now classified as G. beringei.

The eastern gorilla is a large hominid with a large head, broad chest, and long arms. It has a flat nose with large nostrils. The face, hands, feet and breast are hairless. The fur is mainly black, but adult males have a silvery “saddle” on their back. When the gorilla gets older, the hair on the saddle of the back becomes white, much like the gray hair of elderly people. This is why the older males are called silverbacks. Grauer’s gorilla has a shorter, thicker, deep black fur, while the mountain gorilla has a more bluish color. The mountain gorilla is slightly smaller and lighter than Grauer’s gorilla, but still larger and heavier than the western lowland gorilla and the Cross River gorilla. Males are much larger than females. A full-grown adult male Eastern gorilla typically weighs 140–205.5 kg (309–453 lb) and stands 1.7 m (5.6 ft) upright and a female typically weighs 90–100 kg (200–220 lb) and stands 1.5 m (4.9 ft) tall. The tallest silverback recorded was a 1.94-metre (6.4 ft) individual shot in Alimbongo, northern Kivu in May 1938. The heaviest gorilla recorded was a 1.83-metre (6.0 ft) silverback shot in Ambam, which weighed 266 kilograms (586 lb) although the latter area is within the range of the western gorilla, far outside that of the eastern gorilla.

Mountain gorillas are restricted to the mountain rainforests and subalpine forests of eastern Democratic Republic of the Congo, southwestern Uganda and Rwanda. Grauer’s gorilla occurs across the forests of the Albertine Rift in eastern DRC.

Eastern gorillas are herbivorous, with a heavily foliage based diet, due to lack of available fruit in their habitats. They have smaller home ranges than western gorillas as foliage is more abundant than fruit. They are diurnal but the majority of foraging occurs in the morning and late afternoon. At night they build nests by folding over vegetation, usually on the ground.

Eastern gorillas live in stable, cohesive family groups, led by a dominant silverback male. Eastern gorillas tend to have larger group sizes than their western relatives, numbering up to 35 individuals. There is no distinct breeding season and females give birth only once every 3–4 years due to the long period of parental care and a gestation period of 8.5 months. Newborn gorillas have grayish-pink skin and can crawl after 9 weeks; they are not fully weaned until 3.5 years. Males defend their females and offspring using their large size in intimidating displays involving charging and chest-beating.

The eastern gorilla has become increasingly endangered since the 1990s, and the species was listed as critically endangered in September 2016 as its population continued to decrease. Illegal hunting for bush meat and destruction of their habitat as a result of intensifying forestry and the development of agriculture form the most important threats for the species. Between 1996 and 2016, the eastern gorilla lost more than 70 percent of its population, and by 2016 the total population was estimated to be less than 6,000.

The only exception is the mountain gorilla subspecies, which is also critically endangered but saw its population increase to about 880 individuals in 2016. In some national parks, viewing mountain gorillas is a popular tourist attraction. These national parks include Volcanoes National Park in Rwanda, Virunga National Park in the Democratic Republic of the Congo, and Mgahinga Gorilla National Park and Bwindi Impenetrable National Park in Uganda.

Unlike the western lowland gorilla, there are few eastern gorillas in zoos. The Antwerp Zoo is the only zoo outside the native range of the species that has eastern lowland gorillas. Outside the native range, the mountain gorilla is not held in captivity at all. Small groups consisting of animals confiscated from poachers are kept in the Democratic Republic of Congo: Grauer’s gorillas at the Gorilla Rehabilitation and Conservation Education (GRACE) center in Tayna Nature Reserve and mountain gorillas at the Senkwekwe Center in Virunga National Park.

The World Conservation union lists the western gorilla as critically endangered, the most severe denomination next to global extinction, on its 2007 Red listed of threatened species. The Ebola virus might be depleting western gorilla populations to a point where their recovery might become impossible, and the virus decimated populations in protected areas by 33% from 1992 to 2007, which may be equal to a decline of 45% for a period of just 20 years spanning 1992 to 2011. Poaching, commercial logging and civil wars in the countries that compose the western gorillas’ habitat are also threats. Furthermore, reproductive rates are very low, with a maximum intrinsic rate of increase of about 3% and the high levels of decline from hunting and disease-induced mortality have caused declines in population of more than 60% over the last 20 to 25 years. Rather, under the optimistic estimate scenarios, population recovery would require on the order of 75 years. Much sooner, perhaps 20 to 30 years in the future, habitat loss and degradation from agriculture, timber extraction, mining and climate change will become a major threat. Thus, a population reduction of more than 80% over three generations (i.e., 66 years from 1980 to 2046) seems likely

In the 1980s, a census taken of the gorilla populations in equatorial Africa was thought to be 100,000. Researchers adjusted the figure after years of poaching and deforestation had reduced the population to approximately 50,000.

Surveys conducted by the Wildlife conservation society in 2006 and 2007 found around 125,000 previously unreported gorillas have been living in the swamp forests of Lake Tele Community Reserve and in neighboring Marantaceae (dry land) forests in the DR Congo. This discovery could more than double the known population of the animals, though the effect that the discovery will have on the gorillas’ conservation status is currently unknown. With the new discovery, the current population of western lowland gorillas could be around 150,000–200,000. However, the gorilla remains vulnerable to Ebola, deforestation and poaching.

Estimates on the number of Cross River gorillas remaining is 250–300 in the wild, concentrated in approximately 9-11 locations. Recent genetic research and field surveys suggest that these locations are linked by the occasional migration of individual gorillas. The nearest population of western lowland gorilla is some 250 km away. Both loss of habitat and intense hunting for bush meat have contributed to the decline of this subspecies. A conservation plan for the Cross River gorilla published in 2007 outlined the most important actions necessary to preserve this subspecies.

There are two subspecies of Eastern gorillas: namely

Species: Eastern Lowland Gorilla
Scientific name: Gorilla beringei graueri
Location: Democratic Republic of Congo
Population: Less than 3000
Conservation status: Endangered
Physical characteristics: Largest of gorilla sub species, longer arms than the mountain gorilla and shorter hair and teeth.

Species: Mountain Gorilla
Scientific name: Gorilla beringei beringei
Population: Less than 720
Conservation Status: Critically Endangered
Physical characteristics: Large skull, wide face and angular nostrils. Larger body and longer hair than eastern lowland gorilla

The Western gorillas

Western gorillas are generally lighter colored than eastern gorillas. Western lowland gorillas have black, dark grey or dark brown-grey fur with a brownish forehead. Measurements of wild individuals show that mature males average 155 cm (61 in) in height, while mature females average 135 cm (53 in), weights of wild individuals have been rarely taken but captive western gorillas average 157 kg (346 lb) in males and 80 kg (176 lb) in females. The Cross River gorilla differs from the western lowland gorilla in both skull and tooth dimensions.

Western gorillas live in groups that vary in size from two to twenty individuals. Such groups are composed of at least one male, several females and their offspring. A dominant male silverback heads the group, with younger males usually leaving the group when they reach maturity. Females transfer to another group before breeding, which begins at eight to nine years old; they care for their young infant for the first three to four years of its life. The interval between births, therefore, is long, which partly explains the slow population growth rates that make the western gorilla so vulnerable to poaching. Due to the long gestation time, long period of parental care, and infant mortality, a female gorilla will only give birth to an offspring that survives to maturity every six to eight years. Gorillas are long-lived and may survive for as long as 40 years in the wild. A group’s home range may be as large as 30 square km, but is not actively defended. Wild western gorillas are known to use tools.

Western gorillas’ diets are high in fiber, including leaves, stems, fruit, piths, flowers, bark, invertebrates, and soil. The frequency of when each of these is consumed depends on the particular gorilla group and the season. Furthermore, different groups of gorillas eat differing numbers and species of plants and invertebrates, suggesting they have a food culture. Fruit comprises most of the gorillas’ diets when it is abundant, directly influencing their foraging and ranging patterns. Fruits of the genera TetrapleuraChrysophyllumDialium, and Landolphia are favored by the 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 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 lowland gorillas’ diets, which seem to have some sort of cardiovascular health benefit for lowland gorillas, and are a known part of the natural diets for many wild populations.

There are two subspecies of Eastern gorillas: namely

Species: Western Lowland Gorilla
Scientific name: Gorilla gorilla gorilla
Location: Democratic Republic of Congo
Population: 100,000
Conservation statuses: Critically Endangered
Physical characteristics: Males silverback coloring extends onto the thighs also have redder hair on their heads.

Species: Cross River Gorilla
Scientific name: Gorilla gorilla diehli
Population: Approximately 300
Conservation Status: Critically Endangered
Physical characteristics: Smaller skull and teeth than other gorilla as well as shorter hands and feet.

Physical Characteristics of gorillas

Gorillas are quadruped meaning they move around by walking on their knuckles, their huge arms provide balance and support for their large frames. Size and weight varies between species and gender, with males reaching heights of 1.7 m when stood tall and weighing between 170 kg to 240 kg. Females usually weigh between 70 kg to 100 kg and are shorter reaching heights of 1.5 m.

Several million years ago the gorilla split from its closest living relative the chimpanzee. It is thought that originally gorilla were just one species, but changed as they spread and adapted to different living conditions.

As gorillas are ground dwelling they have evolved without a tail, which is used by other primates for balancing and gripping when climbing trees. They have good hearing, which is necessary in thick vegetation where visibility can be poor and good eyesight which they use to identify food.

Social structures of gorillas

Gorilla’s live in groups called a troop, which can be made up of 2- 40 animals. Within this group there is one dominant silverback male several females and younger males and offspring of different ages.

Silver backs

Large adult male with distinctive silver colored hair on their back. This is developed through maturity and is usually present on male Gorilla’s over 12 years of age. An adult silverback can weigh over 180 kg and is the biggest and heaviest of all living primates. As the leader of the group the dominant silverback is in charge of protecting its troop from predators or rival silverbacks, displaying a broad chest and large canine teeth when threatened. The dominant silverback is also in charge of finding good places to forage for food and safe places to rest and sleep. If the dominant silverback dies then a troop will disband and form new groups.

Black backs

Younger male gorillas are called black backs because they have not yet developed silver hair on their back like mature males, though all males will not necessarily develop a silver back. They support the leader and help them forage. When they reach sexual maturity at the age of ten they leave their family groups to join another or form their own and find a mate. They usually travel alone or with a group of other males until they can attract a mate.

Females

Females leave their family groups when they reach sexual maturity in order to prevent in breeding. They can join lone male or other females and within groups are ranked according to when they joined the group; this rank is passed on to their offspring. They form strong relationships with males through behavior such as grooming, which is important as male gorillas provide protection from predators.

Juveniles and Infants

Young infants are playful and inquisitive, and for the first 3-4 years of their lives they have close bond with their mother. Juveniles will groom each other and the dominant silverback will groom juveniles and protects them.

Relationships

Gorillas are social animals and within troops exists different relationships. All females in the troop have a strong relationship with the dominant silverback, which is strengthened through bonding activities such as grooming. However males and females are often aggressive to each other, though it rarely results in death.

Female to female relationships are not strong and often aggressive fighting occurs over access to males. Relationships between males are not strong because of dominance issues however within all male groups individuals are friendlier with each other.

Gorillas are tolerant of other species and would only attack if they felt threatened. They are wary of humans and it takes a long time to build their trust.

Daily activities

Gorillas walk around 1 km each day at a slow pace foraging for food. They wake up early between 6-8 am and spend the day eating and playing and relaxing. Each evening between 5-6 pm they build a bowl shaped nest from leaves and vegetation to sleep in, which keeps them warm and only a mother and her offspring share a nest.

Intelligence

Language

Some gorillas in captivity have been taught to communicate with humans. As part of a gorilla language project, Koko a western lowland gorilla has been taught American Sign Language and has mastered 1,000 words.

Use of tools

Younger male gorillas are called black backs because they have not yet developed silver hair on their back like mature males, though all males will not necessarily develop a silver back. They support the leader and help them forage. When they reach sexual maturity at the age of ten they leave their family groups to join another or form their own and find a mate. They usually travel alone or with a group of other males until they can attract a mate.

Diseases and threats

Recent research has shown that the parasite Plasmodium falciparum that aggressively infects millions of humans each year has been found in gorillas, along with two new species of malaria parasites (Plasmodium GorA and Plasmodium GorB). Plasmodium falciparum originated from a closely related parasite found in chimpanzees in equatorial Africa and is responsible for 85 percent of malaria infections in humans and nearly all deaths from the disease. Increase in logging, deforestation, and bush meat hunting favors the transmission of new parasites to humans from gorillas and vice versa.

Ebola virus is extremely lethal for humans and other great apes including gorillas. Between 2001 and 2005, at least 5,500 were killed at the Lossi Sanctuary in northwest Republic of Congo. Recorded outbreaks of the Ebola virus since 2000 might have claimed thousands of gorillas in Africa. It is unclear how the disease is spread but likely through the butchering and handling of primate bush meat. Mountain gorillas have not yet been affected. The conservation implications of Ebola virus are significant since past outbreaks have occurred mainly in remote protected areas that were the stronghold for gorilla protection.

Threats

Bush meat trade

In some parts of Africa gorillas are hunted for their meat. Animals are caught using snares or riffles and taken to markets usually far away. Sometimes gorillas are unintentionally caught in snares designed to trap other animals. Though such trade is illegal, people go to great lengths to avoid detection and trade can be difficult to monitor. In particular western species of gorilla have been most affected by the bush meat trade. A recent undercover investigation conducted by Endangered Species International has found that up to two gorillas are killed and sold as bush meat each week a region of the Republic of Congo.

Habitat Loss

Destruction of forest areas due to commercial logging and agriculture is having a huge effect on gorilla populations. Approximately 80% of gorillas live in unprotected areas and are therefore exposed to human influence on their environment. The opening up of new areas for industries has brought a new labor force into remote areas, where bush meat is hunted for sustenance. Improved infrastructure such as the building of roads has also given illegal trappers easier access to gorillas and caused habitat destruction. Accidental or uncontrolled bushfires can also spread through habitats stripping areas of vegetation that gorillas could feed on. Due to their shy natures and wariness of humans gorillas are pushed into smaller areas away from human activity.

Conflict/ Civil war

In the past war has forced refugees into areas of gorilla habitat and with limited access to food people are pressured to hunt for bush meat. Human presence in areas of gorilla habitat also increases the risk of human to gorilla disease transmission. With political instability and limited funding monitoring and protecting gorilla populations becomes difficult.

Pets/Souvenirs

Some gorillas are hunted for their body parts for medicinal use and hands, skulls and feet are sold illegally as souvenirs. In some cases infants are stolen to be sold as pets, in these situations adults are usually killed as they will fight to the death to protect their young.

How to Conservation gorillas

All species of gorilla are listed by the International Union for Conservation of Nature and Natural Resources (IUCN) as endangered with the Cross River Gorilla and Mountain Gorilla listed as critically endangered, with some populations showing a decreasing population trends. Several measures have been taken by governments and nongovernmental organizations to combat the major threats of habitat loss, disease and poaching. Below are some of the steps that are being taken to prevent further population decrease.

Education is an important tool for making people aware of the importance of conserving gorillas. Many organizations like Endangered Species International run outreach programmes teaching people ways to protect gorillas, their value and ways to improve hygiene to stop the spread of disease.

Combat disease with the development of vaccinations. At present scientist are developing a vaccination against Ebola however this would be very expensive to implement.

Increased protection is needed to protect gorillas from poachers. An increase in the number of forest rangers, areas of protection and better monitoring of populations is much needed to prevent further deaths from hunting and disease.

Eco Tourism can provide money which can be directed towards environmental initiatives and provide locals with alternative sources of income. However in the case of gorillas it must be strictly controlled to prevent the spread of disease and disturbance to the animals.