LOWLAND GORILLAS - Expeditions Ducret

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LOWLAND GORILLAS

Lowland gorillas in Congo forest : threatened species but still in large numbers in Congo Brazzaville

The western lowland gorilla is certainly the most numerous and widespread of all gorilla subspecies: the latest census reports a much larger population than expected. Despite everything, it remains a threatened space on which many pressures weigh. It is estimated that the gorilla population disappears at a rate of 2.7% per year and between 2005 and 2013, 19.4% of their population would have already disappeared. According to experts, this trend can be reversed if the right policies are put in place.

Inhabiting some of the densest and most remote rainforests in Africa, their numbers have often been underestimated. Significant populations still exist, including in isolated swamps and remote swamp forests in the Republic of Congo. A study carried out over 11 years on 59 sites in five countries was able to estimate in 2018 the number of western lowland gorillas at nearly 360,000 individuals. Previous estimates have been between 150,000 and 250,000 individuals. This population is distributed in the Congo Basin between Cameroon, the Central African Republic, the Democratic Republic of Congo, Equatorial Guinea as well as in large areas in Gabon and the Republic of Congo. The latter alone would have nearly 50% of this population of great apes, 80% of which live outside protected areas.

What threats to the species?

Poaching remains the main threat to their survival, ahead of disease and the loss of their natural habitat. More efforts to combat poaching, both inside and outside protected areas, better land use planning and the development of tourism could allow a better valuation of the species and help in the preservation of the natural habitat of these animals.

Western lowland gorillas: how to identify them?

Western lowland gorillas are distinguished from other gorilla subspecies by their slightly smaller size. They can measure up to 1.70 meters for males and 1.3 meters for females and weigh up to 180 kg for males and 70 kg for females. Their coat is gray-brown and their orange-red forehead. The males have a silver coat from the nape to the rump down to the hair of the foot. They have a larger skull with more pronounced brow ridges and smaller ears than its eastern cousin.

Humans, chimpanzees, orangutans, bonobos and western lowland gorillas: who is man's closest cousin?

An international team of several dozen biologists and geneticists have compared the genomes of four modern “great apes”, rare survivors of the great family of Hominids. Chimpanzees are undoubtedly the closest relatives of humans, with 96% of common genes. The results of this study published in 2012 in the British journal Nature proves that this is certainly true according to the analyses, but only in 70% of cases. In fact, 15% of the human genome is closer to that of the gorilla than that of the chimpanzee. And 15% of the chimpanzee’s genome is in turn closer to that of the gorilla than to that of man. According to the calculations of the international team, gorillas would have diverged from humans and chimpanzees here about 10 million years, the separation between the human species and that of chimpanzees dating back to some 6 million years.

What do gorillas eat?

Like most other primates, gorillas are vegetarians but also insectivores. They spend a good part of their day feeding, moving around in search of berries, stems, leaves, bark or fruit that they find in the forest. It is not uncommon to see them climb trees to grab the fruits they love. In swamps or clearings, they feed on mineral-rich aquatic plants. Insects like termites and ants are also its usual diet. The gorilla eats almost 20 kg of food every day.

How do western lowland gorilla groups live?

Western lowland gorillas are very gregarious animals living in mixed hierarchical groups comprising 2 to 20 individuals (on average 8). The group is structured around a dominant silverback, which plays the role of protector and parent. Several females and their young make up the group. Sometimes non-dominant males also join the group. The dominant is however the only male in the group able to mate. Females can also leave the group if they consider that the silverback is not fulfilling its function. Young males also sometimes form separate groups of bachelors, waiting to be able to form a group in their turn.

The groups live on an area of more or less 30km². On the same area can live several groups. However, it happens to see two silverbacks fighting to recover part of the harem. When retrieving females, the silverback will often kill the young to breed more quickly with new females. After that, some females may decide to leave the group and start a new group with a new dominant, previously unmarried male.

It is often the female who ensures the formation of the young for several years. She will teach him how to eat, how to behave and how to survive. The father often participates very little in the education of the young, but protects them in case of attack. However, it is not uncommon to see the silverback spending long hours with the little ones.

Gorillas have a low reproductive rate. Sexual maturity for males is around 18 years and 11 years for females. The period between two pregnancies can last 5 or 6 years. Young western lowland gorillas are weaned from breast milk at around 4 years of age, which is very late compared to other mammals. The lifespan in the wild is 35-40 years. Their main adversary, in addition to the diseases that affect the youngest more, is the leopard which prowls in the tropical forests.

Gorillas communicate with each other using cries, facial expressions and attitudes. In case of disturbance or aggression, the male tries to impress the intruder by shouting and hitting his chest with his fists. In the extreme case, he may run towards the intruder and bite him. This is what scientists can experience during the process of habituation of a group to the human presence. The process can last between 3 and 5 years with daily visits.

How to observe gorillas in the Republic of Congo?

Congo Brazzaville is the country with the highest number of western lowland gorillas. About 200,000. For the past thirty years, scientists have established camps in different reserves to conduct research on this great primate from Central Africa.

It is naturally possible to come across it in the forest, especially in the Sangha. To observe them closely, on the other hand, you have to go to the large parks such as the Nouabalé-Ndoki Park, where three groups are followed by scientists and thus accustomed to the human presence.

During the cruises that we offer in the heart of the tropical forest, we go to the Mondika scientific camp in the Nouabalé-Ndoki Park, where it is possible to track one of the three clans in a small group of four people. For about an hour, it will be possible to observe the group of gorillas at a distance of 7 to 10 meters.