How Many Mountain Gorillas Are Left? A Conservation Success

The latest mountain gorilla count

Mountain gorillas (Gorilla beringei beringei) are a subspecies of the eastern gorilla and live in just two isolated populations. Each is counted separately, every several years, in a census run by the wildlife authorities of Rwanda, Uganda and the Democratic Republic of the Congo (DRC) with conservation partners.

These figures were announced in 2018 and 2019 and are the most widely cited totals. Because gorillas live in steep, dense forest, counts are minimum figures; a few groups may be missed, and new counts may show different numbers.

How do scientists count mountain gorillas?

Teams of rangers, trackers and researchers sweep systematically through the forest looking for fresh trails and night nests. Every evening each adult gorilla builds its own nest, so counting nests at a site gives the size of a group, and the size of dung found in the nests shows whether it belongs to a silverback, a female or a youngster.

Since the mid-2000s, censuses have also used genetic analysis. Dung samples are collected and their DNA is used to identify individual gorillas, so the same animal is not counted twice. Many groups are also habituated, meaning they are used to people, and are followed daily by trackers who know every member.

From around 250 to over 1,000: the recovery

In the 1960s and 1970s, mountain gorillas were in steep decline because of poaching, the capture of infants for zoos and collectors, and the clearing of forest for farming. In 1981 a census in the Virungas found only about 254 gorillas.

Since then the Virunga population has grown steadily, to about 320 in 1989, 380 in 2003, 480 in 2010 and 604 in 2015–2016. The Bwindi population has also increased over recent decades. In 2018 the IUCN moved the mountain gorilla from Critically Endangered to Endangered, a rare improvement for a great ape. The species as a whole, the eastern gorilla, is still Critically Endangered because its other subspecies, Grauer’s gorilla, has declined sharply.

Why did mountain gorilla numbers rise?

Several things worked together:

• Research and protection: Dian Fossey began studying mountain gorillas at her Karisoke Research Center in Rwanda in 1967, and pushed for active anti-poaching patrols. Her work, and her book Gorillas in the Mist, drew worldwide attention. Rangers in all three countries now patrol daily and remove thousands of snares.
• Tourism: gorilla tracking began in Rwanda in the late 1970s and is now a major source of income. A permit costs US$1,500 per person in Rwanda, and a share of park revenue goes to local communities, giving people a reason to protect gorillas.
• Veterinary care: the organization now known as Gorilla Doctors has treated wild mountain gorillas since 1986, removing snares and treating serious illness and injuries caused by people. Studies suggest this care has contributed to the population’s growth.
• Cross-border cooperation: Rwanda, Uganda and DRC coordinate protection of the Virunga Massif, supported by groups such as the International Gorilla Conservation Programme, founded in 1991.

What still threatens mountain gorillas?

The recovery is fragile. About 1,060 animals in two small areas could be hit hard by a single disaster.

• Disease: gorillas are closely related to humans and can catch human respiratory infections, which are a leading cause of death in habituated groups. Visitors keep at least 7 m (23 ft) away, and many parks require masks.
• Snares: traps set for antelopes still injure and kill gorillas.
• Limited space: the parks are surrounded by some of the most densely populated farmland in Africa, so the gorillas cannot expand into new areas.
• Conflict: armed groups have operated in and around Virunga National Park for decades. More than 200 rangers have been killed protecting the park, and fighting has at times cut off access to gorilla areas.
• Low genetic diversity: the small, isolated populations show high levels of inbreeding, although so far they appear to have avoided its worst effects.

How do other gorillas compare?

Mountain gorillas are rare, but they are not the rarest gorilla. Of the four subspecies, the Cross River gorilla has only about 250–300 animals, and Grauer’s gorilla, the mountain gorilla’s eastern relative, was estimated at about 3,800 in 2016 after a decline of around 77 percent in two decades, although a later survey suggested numbers might be higher. Western lowland gorillas are by far the most numerous, at an estimated 360,000 in a 2018 study, but they are also declining. Learn about the western gorilla and the ranges of all four subspecies in Where do gorillas live?

Can mountain gorillas keep recovering?

Female gorillas usually have their first infant at about 10 years old and then give birth only once every four years or so, so populations grow slowly even under good protection. With strong protection, healthy tourism and continued support from local communities, conservationists hope numbers will keep rising. The mountain gorilla story shows that even a very small population of a slow-breeding animal can recover when people work together for decades.