Mt Tshiaberimu Conservation Project
A small population of Eastern gorillas, once believed to be their own sub-species, Gorilla rex pygmalion, live within Congo’s Virunga National Park, on the steep slopes of Mt Tshiaberimu. At 2,900 m, Mt Tshiaberimu, or ‘Mountain of the Spirits’, is the highest point on the western escarpment of the Albertine Rift, rising a staggering 1,700 m above Lake Edward, Semliki River, and the Rwizi Plains, which separate it from the Rwenzoris (see map and satellite image).
Because this rare gorilla population is isolated from other gorilla habitats in the Rift, Mt Tshiaberimu is a conservation area of great scientific importance.
In 1998, when with a donation from bestselling author Michael Crichton the Gorilla Organization started supporting their protection, there were only 16 gorillas remaining on the mountain. Ten years later, after an intensive programme of community-based projects and close monitoring by teams of rangers, the population had increased by 25% to 20.
Background and Findings
During the early part of this century, the massif to the west of Lake Edward was covered with more than 450 km2 of rich montane forest. Although it is probably a considerable over-estimate, Johnson (1931) suggested that 20,000 gorillas (Gorilla gorilla) lived in the region as a whole. Today, all that is known to remain of this montane forest is about 60 km2 off the northwest corner of the Lake. This area, known as Mt. Tshiaberimu (c. 1,850 – 3,100 m ), is located within the northern sector of the Parc National des Virunga in eastern Zaire.
In 1959, Schaller (1963) spent two weeks on Mt. Tshiaberimu and found considerable habitat destruction by farmers as well as hunting of gorillas for food in areas adjacent to the park. He located 20 gorillas in four groups and estimated that the total population was no more than 40 animals. Dr. Conrad Aveling (pers. comm.) conducted a survey of the gorillas on Mt. Tshiaberimu in 1986 and concluded that no more than 20 individuals remained.
From May 30th through June 7th 1995 we undertook a preliminary ecological survey of Mt. Tshiaberimu in the area above 2,500 m. Our main objective was to determine the numbers and distribution of gorillas in this highly isolated population. This work was supported by Berggorilla and Regenwald Direkthilfe, and by Zoo Atlanta.
Three teams of guides, rangers and researchers searched Mt. Tshiaberimu for seven consecutive days. Groups of four and 11 gorillas, plus one lone adult male, were located. We conclude that the total number of gorillas remaining here is 16 – 18, and that only two groups occur. They use an area of roughly 18 km2 at 2,800 to 2,900 m in the southwest corner of Mt. Tshiaberimu. This is a region dominated by high bamboo Arundinaria alpina and large podocarpus Podocarpus latifolius. Notably, we found gorillas ranging at elevations considerably higher than the 2,600 m reported by Schaller (1963). Extensive agriculture at the lower elevations surrounding Mt. Tshiaberimu is probably restricting gorillas to the higher elevations and limiting the size of this population.
Mt. Tshiaberimu holds the only sizable natural forest remaining in the region. Although it is part of the Parc National des Virunga, the corridor connecting it to the main (savanna) portion of the park has been encroached upon and destroyed. There is extensive agricultural encroachment around the entire boundary of Mt. Tshiaberimu. This encroachment is, undoubtedly, the greatest single threat to the area and its gorillas.
Pit-sawing is another serious problem as more than 500 large podocarpus trees have been pit-sawn during the last few years. Poaching is at a low level at this time, but this is probably due to the paucity of prey rather than to any restraint by the poachers. Although there was extensive gold prospecting in the rivers of Mt. Tshiaberimu in the recent past, this activity is now also at a greatly reduced level. Gold mining is said to have been accompanied by heavy poaching.
In addition to gorillas, we saw, or found evidence of, blue monkey (Cercopithecus mitis stuhlmanni), L’Hoest’s monkey (Cercopithecus lhoesti), black- fronted duiker (Cephalophus nigrifrons), yellow-backed duiker (Cephalophus sylvicultor), elephants (Loxodonta africana) and golden cat (Felis aurata). Signs of elephant were abundant throughout the area between 2,600 and 3,100 m. The rangers estimate that about 30 elephants remain on Mt. Tshiaberimu. There is probably no movement of elephants, or any other species of medium to large mammals, between this area and other parts of the park as the former corridor is farmed, and densely populated with people.
Conservation Action
Since the survey, a preliminary report of the findings with an assessment of the conservation status of Mt. Tshaibarimu has been written and widely distributed. Berggorilla and Regenwald Direkthilfe, and The Dian Fossey Gorilla Fund are presently purchasing two sets of equipment (uniforms, rain- gear, boots, backpacks, warm clothing, etc.) for the two wardens and 10 rangers working at Mt. Tshiaberimu. One set will be delivered during the first half of 1996 and the second set during the second half of 1996. In July 1996 we plan to return to Mt. Tshiaberimu with members of the Karisoke Research Center to recensus the gorillas and reassess our preliminary findings. We will also meet with officals of the Institut Zairois pour la Conservation de la Nature and local community leaders to discuss future conservation action for the area.
During this second trip we hope to spend a few weeks surveying areas from 1,950 to 2,500 m within the reserve in order to obtain more information on the biodiversity values of Mt. Tshiaberimu. While this lower sector of Mt. Tshiaberimu is known not to hold gorillas, it is probably home to several bird species endemic to the Albertine Rift Afromontane Region and several additonal species of primates (e.g., red colobus Procolobus badius, Angolan black-and-white colobus Colobus angolensis, chimpanzee Pan troglodytes, eastern needle-clawed galago Euoticus inustus, dwarf galago Galagoides demidovii, Thomas’s galago Galagoides thomasi, Bosman’s potto Perodicticus pottos. We believe that Mt. Tshiaberimu will prove to be an important conservation area both for its gorillas and for its biodiversity.
While many of the areas where gorillas were collected on this massif in the past are under heavy cultivation (e.g., Alimbongo, Ibatsero), a few may still have some montane forest and, perhaps, gorillas. We plan to visit several of the more promising areas (e.g., Mt. Malulu, Matembe, Kassinga, Lumboku River) in June/July, 1996 in order to determine whether any additonal montane forest and gorillas can be located.
The taxonomic status of the Mt. Tshiaberimu gorillas remains uncertain. Although Groves and Stott (1979) has placed animals from this population under G. g. graueri, he emphasised that they appear to be intermediate between beringei and graueri, although tending more towards graueri. Originally these gorillas were described as a different subspecies G. g. rex-pygmaoreum by Schwarz (1927). This was based on their short body and facial hair, large body size and robust supraorbital ridges. Although they range at altitudes widely overlapping those of the Virunga gorillas (G. g. beringei), and also share limited use of arboreal foods and substrates with Virunga gorillas, they have markedly different body proportions, suggesting considerable population differences. Together with Dr. Jose Braga of the University of Brodeaux, we are presently preparing a paper on the taxonomic status of the Mt. Tshiaberimu gorillas based upon new, uncatalogued, skeletal material.