IUCN Status: Critically Endangered

The critically endangered eastern lowland gorilla, or Grauer’s gorilla, is a subspecies of the eastern gorilla (the other being its cousin the mountain gorilla), which resides exclusively in eastern Congo’s tropical rainforests. Its habitat is continually threatened, meaning the world’s largest primate is being pushed into an ever shrinking range.

Eastern Lowland Gorilla Facts

    01
    Habitat

    It now occupies just 13% of its historical range, and it’s estimated that the population has decreased by more than 50% since the mid-90s.

    The lowland gorillas of Virunga live in a small, isolated forest on Mount Tshiaberimu, just 77 square km in size, situated northwest of Lake Edward.

  • 01
    Habitat

    Eastern lowland gorillas typically reside in lowland rainforests, but can also live in dense montane forests as long as the climate is still tropical. It is also possible for them to inhabit swampland if the right vegetation grows there. As a consequence of armed conflict and illegal resource exploitation, the subspecies’ range is rapidly decreasing.

  • 02
    Behavior

    Eastern lowland gorillas, like other subspecies of gorilla, eat up to 18 kg of vegetation a day. Since their diet is rich in moisture, they rarely need to drink any water.

    They supplement their diets with very small servings of insects, such as ants and termites.

  • 02
    Behavior

    While mothers care directly for infants, who take 8.5 months to develop in the womb, the powerful silverback, the group’s dominant male, offers protection from external threats. He also takes time to play with his offspring, aside from leading the group of up to 30 individuals to nesting and feeding sites.

  • 03
    Physical Characteristics

    The dominant male within a troop is known as silverback, because of the swathe of silver hair which blankets its rear when he reaches sexual maturity at around twelve years of age. The fur of females and non-mature males is dark and shorter than that of mountain gorillas.

    They have long arms and their thumbs extend further than their fingers.

  • 03
    Physical Characteristics

    Of the four subspecies of gorilla, the eastern lowland is physically the largest. They have stocky bodies, large hands and bulky skulls compared to the rest of the body. On average, males grow to be 359 pounds (163 kg) and 5.5 feet tall (1.69 m), with females weighing in at 178 pounds (81 kg) and reaching 5.2 feet (1.6 m).

A Critically Endangered Population at a Turning Point

The eastern lowland gorillas of Mount Tshiaberimu in Virunga National Park remain critically endangered, threatened by ongoing habitat loss and human activity. As of October 2024, the isolated population had dwindled to just eight individuals.

In a major conservation milestone, four rescued female gorillas from GRACE (Gorilla Rehabilitation and Conservation Education Center) were reintroduced to the area in December 2024. This effort offered a vital opportunity to strengthen the group and prevent local extinction. With their arrival, the population in Mount Tshiaberimu has increased to twelve.

The long-term survival of these gorillas now depends on continued protection from Virunga’s field teams, close collaboration with nearby communities, and the ongoing support of dedicated conservation partners.

Kipura & Katsabara Families
  • Mwasa

    Silverback of the Kipura Family

  • Mwengesyali

    Female of the Kipura Family

  • Kavango

    Juvenile of the Kipura Family

  • Ndijingala

    Female introduced to the Kipura Family

  • Mapendo

    Female introduced to the Kipura Family

  • Lulingu

    Female introduced to the Kipura Family

  • Isangi

    Female introduced to the Kipura Family

  • Katsabara

    Silverback of the Katsabara Family

  • Mukokya

    Female of the Katsabara Family

  • Ndekesiri and her newborn

    Female and baby of the Katsabara Family

  • Espoir

    Juvenile of the Katsabara Family

1996

First Population Estimate

Cornet d’Elzius provided the first population estimate, referencing a group of 31 individuals originally discovered in 1958.

2001

Group Division

According to the trackers’ collective memory, a major split occurred in 2001, resulting in the formation of two new groups: Kipura (4 individuals) and Lusenge (11 individuals).

2003

Formation of Katsabara Group

In September 2003, four individuals split from the Lusenge group to form the Katsabara group, led by a dominant male named Katsabara. Following the death of Lusenge’s silverback, the remaining members either became solitary or joined the Kipura or Katsabara groups.

2008

Evacuation of the Area

Following repeated militia attacks, park authorities were forced to evacuate the area. Militias subsequently established a presence, and mining activities intensified.

2010

Veterinary Monitoring

Despite persistent challenges in the area, Gorilla Doctors veterinarians have managed to continue monitoring the gorilla population. In 2010, six individuals were under observation, decreasing to five by 2018, with two in the Kipura group and three in the Katsabara group.

2021

Monitoring Program Launched

A dedicated gorilla monitoring program begins at Mt. Tshiaberimu, led by Virunga Rangers, community trackers, and Gorilla Doctors. The initiative provides vital health and behavioral data on the critically endangered population.

2023

Reintroduction Deemed Essential

Findings from years of monitoring confirm the population’s genetic isolation and lack of long-term viability. Conservation partners and experts agree that introducing gorillas from an external population is critical to prevent extinction and restore genetic diversity.

2024

New Birth Brings Hope to Tshiaberimu

In October 2024, a baby gorilla has been born into the Katsabara family, bringing their group to five individuals and raising the total number of eastern lowland gorillas in the Tshiaberimu area to eight. This birth marks a promising step forward for the conservation of this critically endangered species. The infant's mother, Ndekesiri, remains closely protective of her newborn, and the baby's sex is yet to be confirmed.

2024

Preparing for Reintroduction

In October 2024, in the lead-up to the reintroduction of four female Grauer’s gorillas, final preparations were made at Mt. Tshiaberimu, including checks on medical supplies and equipment. Team members from Virunga, GRACE, and partner organizations coordinated closely to ensure a safe and smooth transfer. On October 22, the gorillas were successfully transported from GRACE to Mt. Tshiaberimu by helicopter - each accompanied by a veterinary specialist. This marked a major milestone in efforts to restore the local gorilla population.

2024

Settling In and First Encounters

In November 2024, the four reintroduced females begin adjusting to their new environment after being transferred to a spacious transitional enclosure, where they explore local vegetation and adapt to the cooler mountain climate. Their health remains stable, and monitoring continues. Mapendo emerges as the lead female. Meanwhile, wild silverback Mwasa, leader of the Kipura group, discovers the females nearby. Though separated by a fence, mutual interest grows - especially from the females, who respond to his vocalizations and even attempt to reach him.

2024

Release Into Wild

In December 2024, forty-two days after the relocation, following positive interactions between the silverback and the four females, the fence surrounding the reintegration facility was taken down, allowing the gorillas to be released into the wild. In the weeks following their release, near-daily health monitoring by Dr. Cédric confirmed that all four reintroduced females are adapting well to their new life in the wild.

2025

Positive Signs for the Future

In March 2025, over a three-month period, Dr. Cédric conducted 30 health assessments of the two gorilla groups in the Mount Tshiaberimu region—Kipura and Katsabara. All 12 Grauer’s gorillas remained in good health, with no veterinary interventions required. The four reintroduced females continue to thrive within the Kipura group, led by silverback Mwasa. They are frequently observed engaging in natural behaviors such as foraging, resting, grooming, and moving together through the forest. A particularly exciting moment occurred when Mwasa and Lulingu were observed mating—an encouraging sign for the future of this critically endangered population.

1996-2010

Early History of the Mt. Tshiaberimu Population

2021-2025

From Monitoring to Reinforcement

1996

First Population Estimate

Cornet d’Elzius provided the first population estimate, referencing a group of 31 individuals originally discovered in 1958.

2001

Group Division

According to the trackers’ collective memory, a major split occurred in 2001, resulting in the formation of two new groups: Kipura (4 individuals) and Lusenge (11 individuals).

2003

Formation of Katsabara Group

In September 2003, four individuals split from the Lusenge group to form the Katsabara group, led by a dominant male named Katsabara. Following the death of Lusenge’s silverback, the remaining members either became solitary or joined the Kipura or Katsabara groups.

2008

Evacuation of the Area

Following repeated militia attacks, park authorities were forced to evacuate the area. Militias subsequently established a presence, and mining activities intensified.

2010

Veterinary Monitoring

Despite persistent challenges in the area, Gorilla Doctors veterinarians have managed to continue monitoring the gorilla population. In 2010, six individuals were under observation, decreasing to five by 2018, with two in the Kipura group and three in the Katsabara group.

2021

Monitoring Program Launched

A dedicated gorilla monitoring program begins at Mt. Tshiaberimu, led by Virunga Rangers, community trackers, and Gorilla Doctors. The initiative provides vital health and behavioral data on the critically endangered population.

2023

Reintroduction Deemed Essential

Findings from years of monitoring confirm the population’s genetic isolation and lack of long-term viability. Conservation partners and experts agree that introducing gorillas from an external population is critical to prevent extinction and restore genetic diversity.

2024

New Birth Brings Hope to Tshiaberimu

In October 2024, a baby gorilla has been born into the Katsabara family, bringing their group to five individuals and raising the total number of eastern lowland gorillas in the Tshiaberimu area to eight. This birth marks a promising step forward for the conservation of this critically endangered species. The infant's mother, Ndekesiri, remains closely protective of her newborn, and the baby's sex is yet to be confirmed.

2024

Preparing for Reintroduction

In October 2024, in the lead-up to the reintroduction of four female Grauer’s gorillas, final preparations were made at Mt. Tshiaberimu, including checks on medical supplies and equipment. Team members from Virunga, GRACE, and partner organizations coordinated closely to ensure a safe and smooth transfer. On October 22, the gorillas were successfully transported from GRACE to Mt. Tshiaberimu by helicopter - each accompanied by a veterinary specialist. This marked a major milestone in efforts to restore the local gorilla population.

2024

Settling In and First Encounters

In November 2024, the four reintroduced females begin adjusting to their new environment after being transferred to a spacious transitional enclosure, where they explore local vegetation and adapt to the cooler mountain climate. Their health remains stable, and monitoring continues. Mapendo emerges as the lead female. Meanwhile, wild silverback Mwasa, leader of the Kipura group, discovers the females nearby. Though separated by a fence, mutual interest grows - especially from the females, who respond to his vocalizations and even attempt to reach him.

2024

Release Into Wild

In December 2024, forty-two days after the relocation, following positive interactions between the silverback and the four females, the fence surrounding the reintegration facility was taken down, allowing the gorillas to be released into the wild. In the weeks following their release, near-daily health monitoring by Dr. Cédric confirmed that all four reintroduced females are adapting well to their new life in the wild.

2025

Positive Signs for the Future

In March 2025, over a three-month period, Dr. Cédric conducted 30 health assessments of the two gorilla groups in the Mount Tshiaberimu region—Kipura and Katsabara. All 12 Grauer’s gorillas remained in good health, with no veterinary interventions required. The four reintroduced females continue to thrive within the Kipura group, led by silverback Mwasa. They are frequently observed engaging in natural behaviors such as foraging, resting, grooming, and moving together through the forest. A particularly exciting moment occurred when Mwasa and Lulingu were observed mating—an encouraging sign for the future of this critically endangered population.

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