Gorillas: Characteristics, Subspecies, Habitat, Reproduction

The gorillas are apes that make up the genus Gorilla . It is a herbivorous animal that lives in forests located in central sub-Saharan Africa, geographically located on both sides of the Congo River.

The Gorilla genus is divided into two species: the western gorilla ( Gorilla gorilla ) which has short, soft, gray or brown fur; and the eastern gorilla ( Gorilla beringei ) that has long black hair.

Gorilla gorilla

These primates have a robust body, with a strong torso. Its face has a distinctive feature and the lower jaw protrudes noticeably over the upper one. In turn, a noticeable sagittal ridge develops on the forehead, where the powerful muscles of the jaw are attached.

The adult male has sharp and prominent fangs. In addition, when it reaches sexual maturity, it has a silver-gray fur between the back and the hip. The group leaders are in charge of directing it, mediating conflicts and ensuring the food and safety of all members of the group.

Article index

  • one

    Gorilla characteristics

    • 1.1

      – Locomotion

    • 1.2

      – Size

    • 1.3

      – Skin

    • 1.4

      – Osseous system

  • two

    Communication

  • 3

    Using the tool

  • 4

     Taxonomy and subspecies

  • 5

    Distribution

    • 5.1

      – Gorilla gorilla

    • 5.2

      – Gorilla beringei

  • 6

    Habitat

  • 7

    State of conservation

    • 7.1

      – Threats

    • 7.2

      – Actions

  • 8

    Reproduction

    • 8.1

      Establishment of groups

    • 8.2

      Mating

    • 8.3

      The babies

  • 9

    Feeding

  • 10

    Behaviour

    • 10.1

      Relations between groups

  • eleven

    References 

Gorilla characteristics

Gorilla beringei beringei

The gorilla is an animal with a robust and powerful build, with an extremely strong and thick torso. Its abdomen is prominent, probably due to the long digestive tract it has, essential for the effective digestion of the fibrous foods it consumes.

In the facial structure, a mandibular prognathism is observed, since the lower jaw protrudes over the upper one. As for the head, it is elongated upwards, the product of a prominent sagittal crest. In addition, it has small ears and eyes.

In its jaw it has 32 teeth, specialized for grinding, cutting and grinding food. Adult males have prominent, sharp fangs of considerable length.

In relation to the extremities, the anterior ones are up to 20% longer and more muscular than the posterior ones. On each leg it has five fingers, with the thumb opposing them. This feature allows you to easily handle objects and food.

One of the peculiarities of this species is that it has fingerprints and nails, instead of claws. Furthermore, the gorilla is a primate that lacks a tail. On the other hand, the adult male has glands under the armpits, which secrete a pungent odor when the animal is stressed, anxious or scared.

– Locomotion

The species that make up the genus Gorilla walk with their knuckles. However, studies show that 61% of mountain gorillas move only with their knuckles, while the rest use their fists, palms and the back of their hands.

On the other hand, these primates can travel short distances bipedally. They tend to do so when their front legs are occupied with food or when they are defensive.

– Size

Weight and height vary according to species, but in all cases, the male is larger than the female. In general, the adult male is between 1.7 and 1.8 meters tall, although it could exceed 1.8 meters.

On the other hand, the male weighs from 136 to 195 kilograms, while the female reaches a maximum of 113 kilograms.

Between species there are also variations. Thus, the Gorilla gorilla measures 1.7 meters and weighs 169.5 kilograms, while the Gorilla beringei is much heavier, being able to reach 200 kilograms.

– Skin

In the Gorilla genus , both skin and fur are dark in color, such as brown, black, or dark gray. The eastern gorilla ( Gorilla beringei ) is generally black and the western gorilla ( Gorilla gorilla ) is grayish or brown.

All species lack hair around the nose, chest, lips, legs, ears, fingers, and on the palms of the hands. Adult males are known as silverback, due to the particular silver fur on their back, which extends to the hips.

This silvery pattern is most striking in eastern gorillas, as it contrasts more with their jet black body. In western gorillas it is not as noticeable, due to the grayish-brown coloration of the body fur.

On the other hand, the hair of lowland species is shorter than that of other gorillas. Likewise, those that live in the mountains, due to the low temperatures, have thick and long fur.

– Osseous system

Group of mountain gorillas

The gorilla’s skeleton is adapted to support the enormous weight of its body. The spinal column has a straighter position, compared to that of the human being. As for the skull, it is large, compared to body size. Inside, towards the back, the brain is housed.

The sagittal crest of this primate is large enough to support the strong muscles that power the jaw. Thanks to this, the animal can chew the tough and fibrous vegetation that is part of its diet.

In relation to the muscles, those found in the shoulders, extremities, back and neck, allow it to have a strength six times greater than that of man.

Communication

Specialists have identified 25 different vocalizations, which are generally used to communicate within the group. Sounds categorized as barking and grunting are used during mobilizations, in order to indicate the location of the troop members.

As for the roars and screams, they are warning or alarm signals. These are vocalized primarily by the silverback male. While the gorilla feeds or rests, it usually emits a deep burp, suggesting satisfaction.

Adult male “silverback” gorilla, in the Congo. Source: Pierre Fidenci / CC BY-SA (https://creativecommons.org/licenses/by-sa/2.5)

Conflicts between these primates are generally resolved by displays and other threatening behavior. The intention is to intimidate the opponent, thus avoiding physical violence.

In this sense, the ritualized loading screen is a unique behavior of gorillas. This behavior develops in nine steps, beginning with a hoot, which becomes progressively accelerated. Next, the primate performs a symbolic feeding and stands up bipedally.

Then, the gorilla usually throws vegetation at the threatening animal, hitting its chest with its front legs and with its fingers arranged in a concave shape. Then he kicks and runs, on two or all fours. Finally it rips through the trees and hits the ground.

Using the tool

Gorilla beringei beringei calf

Experts note that, from a cognitive point of view, the gorilla lacks the adaptability and curiosity of the chimpanzee. However, it has more persistent behaviors.

Members of the genus Gorilla have shown some ability to solve problems and to memorize actions and procedures. Experiences in the laboratory indicate that some gorillas could recognize their image in the mirror, which could be associated with a limited sense of self-awareness.

This primate uses tools to facilitate some tasks in its daily life. Thus, before crossing a swamp, you can take a stick, put it in the water and thus measure the depth.

Also, you could use a piece of tree as a bridge to cross the river or as a support while you take a fruit. In this regard, in the Democratic Republic of the Congo, researchers spotted a two-year-old gorilla using rocks to break up palm nuts.

  Taxonomy and subspecies

-Animal Kingdom.

-Subreino: Bilateria.

-Filum: Cordado.

-Subfilum: Vertebrate.

-Infrafilum: Gnathostomata.

-Superclass: Tetrapoda.

-Class: Mammal.

-Subclass: Theria.

-Infracclass: Eutheria.

-Order: Primates.

-Suborder: Haplorrhini.

-Infraorder: Simiiformes.

-Superfamily: Hominoidea.

-Family: Hominidae.

-Subfamily: Homininae.

-Gender: Gorilla.

Species:

Gorilla beringei.

Subspecies: Gorilla beringei beringei, Gorilla beringei graueri .

Gorilla gorilla.

Subspecies: Gorilla gorilla diehli, Gorilla gorilla gorilla.

D

distribution

Gorillas are unevenly distributed in western and central eastern equatorial Africa. Geographically, the two species are separated by the Congo River.

– Gorilla gorilla

Western gorillas, including the two subspecies, live in Nigeria, Equatorial Guinea, Cameroon, Gabon, the Central African Republic, Angola, the Republic of the Congo, and the extreme west of the Democratic Republic of the Congo.

Gorilla gorilla diehli

Gorilla gorilla diehli. Source: Julielangford / CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0)

Cross River gorillas live in restricted forests and on uneven terrain in distant areas. However, occasionally, they can be located in lowlands, between hills.

This distribution is not associated with a selection based on the availability of food. On the contrary, it could be directly related to high levels of human activity.

The size of the groups is between 2 and 20 gorillas, which inhabit a home range that can cover up to 30 km2. The formation of the groups and the pattern of the habitat range are influenced by several factors. Among these is the distinctly seasonal nature of the Gorilla gorilla diehli habitat .

In this sense, the diet of this subspecies reflects seasonality, where bark and terrestrial herbs are included as a basic diet, throughout the year. During the abundance of fruits, these become an important part of the diet.

Gorilla gorilla gorilla

Gorilla gorilla gorilla. Source: Ltshears / CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0)

Western lowland gorillas inhabit both the swampy and lowland forests of equatorial west Africa. This subspecies is mainly found where there is a predominance of monocotyledonous plants, such as Megaphrynium macrostachyum and Haumania liebrechtsiana.

Regarding the range of home, it is between 10 and 25 km2. The group has an average size of 10 gorillas, but eventually there could be more than 20.

– Gorilla beringei

Geographical distribution in Africa of the Eastern Gorilla (Gorilla beringei). Source: IUCN Red List of Threatened Species, species assessors and the authors of the spatial data. / CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0)

As for the eastern gorillas, and their subspecies, the lowland and mountain gorillas, they are found in Uganda, in various parts of the eastern Democratic Republic of the Congo and in Rwanda.

Gorilla beringei beringei

Male specimen of an eastern gorilla (Gorilla beringei). Source: Fiver Löcker / CC BY-SA (https://creativecommons.org/licenses/by-sa/2.0)

This subspecies is restricted to 2 populations, located in forests, which are 25 kilometers away from each other. However, they are isolated by cultivated lands and urban settlements.

One of the populations is located in the Virunga volcanoes, between the Virunga National Park, the Volcanoes National Park and the Gorilla Mgahinga National Park. The other group lives in the Bwindi Impenetrable National Park in Uganda.

Gorilla beringei graueri

Gorillas of this subspecies are endemic to the forests of the Albertine Rift, located east of the Democratic Republic of the Congo. Thus, it has a discontinuous distribution, ranging from the lowlands, located east of the Lualaba River, to the Itombwe massif and the Mitumba mountains.

Its habitat includes bamboo forests, peat bogs, swamps, subalpine grasslands, and mixed forests. The Gorilla beringei graueri ranges in the broadest altitudinal range than any other gorilla. It is distributed from approximately 600 meters to 2,900 meters above sea level, thus overlapping with G. b. beringei .

Habitat

Gorillas live in a variety of elevations and habitats. Thus, they can be found from swampy ecosystems to montane forests. The eastern species inhabit submontane and montane forests, between 650 and 4,000 meters above sea level.

As for the western gorillas, they inhabit montane forests and lowland swampy forests, from sea level to 1,600 meters above sea level.

State of conservation

Two young Gorilla beringei beringei

The two species of gorillas, Gorilla gorilla and Gorilla beringei , are critically threatened with extinction, according to the IUCN. Their populations have decreased dramatically and consequently, due, among other things, to the fragmentation of their habitat and indiscriminate hunting.

– Threats

Habitat degradation

One of the main problems afflicting gorillas is the alteration of their habitat, motivated by human action. Activities such as logging, agriculture, gathering firewood and grazing destroy the natural areas where this primate lives.

Mining industries in the Democratic Republic of the Congo have devastating effects on ecosystems. On the other hand, ecotourism causes a strong negative impact on nature.

Diseases

Gorillas are susceptible to some of the diseases that afflict humans. For example, these animals are affected by Ebola hemorrhagic fever and mange. Also, they can get respiratory infections, measles, and skin disorders.

Hunting

Gorilla poaching occurs to market their meat and to sell the young at the pet market. Entire groups of gorillas could be killed by some poachers. Faced with a threat, the male hierarch of the group will approach and become visible, becoming an easy prey.

Also, this primate can be annihilated when it ventures into the fields near its habitat, in search of food.

Accidental mortality

Gorillas can accidentally get caught in human traps to capture rodents and pigs. In its struggle to free itself, the primate can injure itself or even cut off some of its limbs completely, causing the death of the animal.

Natural disasters

Cross River gorillas inhabit a small area of ​​forest in Cameroon and Nigeria. In these regions, the dry season lasts for a long time, making the forests susceptible to fires.

Likewise, farmers could start fires in their cultivation plots, in order to eliminate weeds. However, the fire could spiral out of control and spread into the forest, causing irreparable ecological damage.

– Actions

Both the Gorilla gorilla and the Gorilla beringei are included in Appendix I of CITES. Conservation programs include the Great Apes Survival Project, involving UNESCO and the United Nations Environment Program.

In addition to the establishment of national parks, where the species of the Gorilla genus are protected, the implementation of educational programs is important. These should be oriented towards the awareness of the communities towards the protection of the environment and the gorilla.

On the other hand, the maintenance of natural corridors between habitats that are fragmented is of utmost importance to boost gene flow between populations.

Reproduction

The first estrus in the female can occur at approximately six years of age, but then a period of infertility follows, lasting about two years. The estrous cycle lasts between 30 and 33 days. During ovulation, the female has no obvious external signs to indicate to the male that she is receptive to copulate.

As for the male, it is difficult to establish the beginning of reproductive maturity. This is because it is usually fertile before exhibiting any secondary sexual characteristics, such as the silver fur that characterizes the adult male.

However, between 12 and 13 years of age, the male is considered an adult, a state of development that is fully reached at 15 years of age.

Establishment of groups

The vast majority of male gorillas deviate from the birth group, trying to reunite several females and thus form their own family group. This action could bring with it some aggression, since, if the young man invades an already established group and tries to capture the females, in the fight to achieve it the young could die.

There are cases where the male remains in the group where he was born, becoming the second silverback male. Thus, he will be able to reproduce with some of the females and will assume leadership when the leader dies or grows old.

Mating

In the species that make up the genus Gorilla , mating can occur at any time of the year.

The female initiates copulation by pursing her lips, while slowly approaching the male and looking at him for a long time. If he does not respond to your behaviors, you can touch him and hit the ground hard, to get his attention.

Before joining the female, the male touches her and makes a sound known as a train growl. When there are several males in the group, this suggestion could be taken as a preference of the female. However, it usually mates with several males during the heat stage.

The babies

After 258 days of gestation, the calf is born. It weighs around 2 kilograms and is completely defenseless for the first 3 months. During this time, the mother carries her in her arms or climbs on her back.

The newborn is breastfed at least once an hour and sleeps with its mother in the same nest. His separation from his mother is progressive. Thus, between 18 and 21 months of age the young person spends a long time alone, away from the birth group.

Feeding

The gorilla is a vegetarian animal, although some species may occasionally consume some insects. Likewise, the diet varies between species. In this sense, mountain gorillas generally feed on stems, leaves, marrows, and shoots. The fruits are consumed in very small proportions.

Plant species are widely distributed, so there is no competition among gorillas for access to them. Members of this species choose quality foods, high in protein, low in fiber and low in tannins.

In those regions where bamboo is available, it becomes the food of choice. The gorilla burrows into the ground to dig up the tender shoots and eat them.

In relation to western gorillas, the main foods are the pith of Aframomum spp ., The shoots and leaves of the Marantaceae family, and fruits, which constitute about 25% of their diet. In the event that their availability varies, the primate travels to other areas of the habitat in search of them.

Some populations consume aquatic herbs found in swamps. Eventually, the Gorilla gorilla captures and ingests ants and termites, thus supplementing their nutrition.

Behaviour

During the day, the gorilla has very particular activities. In the morning and in the afternoon, this animal mobilizes to look for its food. At noon, he usually rests, taking a nap. Also, you can play with other gorillas or groom each other. At night, it sleeps on its nest, made of leaves and branches.

Species of the genus Gorilla live in groups, known as troops. These can be made up of up to 20 gorillas, but also those of two, an adult male and a female.

The large troops are made up of an adult silverback male, although there may be more than one, several sexually mature females and the young. In the case of mountain gorillas, when the male leading the group dies, another takes his place.

In the eastern lowland gorilla species, if the male silverback is missing, the female and her young are kept together, until a new adult male arrives in the group.

Relations between groups

Females often establish strong relationships with males, with the intention of obtaining opportunities to reproduce and as protection against predators. However, occasionally clashes between males and females may occur, without causing serious injury.

Relationships between females can vary. Those that are gestating are often friendly with each other, while the rest of the females in the group may have some aggressive encounters.

In relation to males, their social ties are weak. Among these primates there are struggles for the hierarchy of dominance and competitions for pairs. Extreme violence can occur very rarely, however, two adult silverback males could be involved in a fight to the death.

References

 

  1. Wikipedia (2019). Gorilla. Recovered from en.wikipedia.org.
  2. Cawthon Lang KA. (2005). Primate Factsheets: Gorilla (Gorilla) Taxonomy, Morphology, & Ecology, Behavior, Conservation. Recovered from pin.primate.wisc.edu.
  3. Encyclopaedia Britannica (2019). Gorilla. Recovered from britannica.com
  4. Alina Bradford (2014). Gorilla Facts. Livescience. Recovered from livescience.com.
  5. Gorillas-world. (2014). Gorillas anatomy. Recovered from gorillas-world.com.
  6. Maisels, F., Bergl, RA, Williamson, EA (2018). Gorilla gorilla (amended version of 2016 assessment). The IUCN Red List of Threatened Species 2018. Recovered from iucnredlist.org.
  7. Plumptre, A., Robbins, MM, Williamson, EA (2019). Gorilla beringei. The IUCN Red List of Threatened Species 2019. Recovered from iucnredlist.org.

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