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Population of Mountain Gorillas in Bwindi Impenetrable National Park, Uganda, Increases To 400 Featured

 

 

A census of mountain gorillas, Gorilla beringei beringei, conducted in 2011 in Bwindi Impenetrable National Park, Uganda, confirms a minimum population of 400 gorillas, raising the world population of mountain gorillas to 880. The official result was released on 13th November 2012 by the Uganda Minister of Tourism, Wildlife, and Antiquities, Hon. Maria Mutagamba alongside representatives of the Uganda Wildlife Authority, Conservation Through Public Health and the International Gorilla Conservation Programme.

The increase in the Bwindi population since the last census, from just over 300 in 2006 to 400 in 2011, is attributed to improved censusing techniques of these rare and elusive apes as well as real population growth. Uganda Wildlife Authority and the parent Ministry stated that the increase in gorilla numbers is due to sound natural resource management practices.

In this latest census, teams systematically moved through Bwindi not once, but twice, looking for and documenting mountain gorilla night nests and faeces, and collecting faecal samples for genetic analysis. The first sweep was conducted with a small team from February 28 to September 2, 2011 and the second sweep conducted with multiple teams from September 10 to November 3, 2011. With the genetic analysis, scientists were able to determine how many unique groups and individuals were found by the field census teams through both sweeps, in what is referred to as a modified mark recapture method.

In short, the two sweeps of Bwindi allowed census teams to find more gorillas than a single sweep would have. Further, it is likely that some gorillas were missed by field census teams in the 2006 census of Bwindi's mountain gorillas. But all signs are that this population of critically endangered mountain gorillas is indeed growing.

“We used to talk about 650 mountain gorillas in the early 1990s when gorilla tourism began in Bwindi and now we are talking about 880 mountain gorillas. This is due to the efforts of effective law enforcement reducing illegal activities in the forest; community conservation where the community has a better understanding and appreciates the benefits of sharing a habitat with mountain gorillas to the extent of tolerating gorillas in their gardens and alerting the park authorities about gorilla poachers; ecotourism where revenue is shared within the community helping to reduce poverty and improve their attitudes to gorilla conservation; veterinarians who ensure that gorillas do not die prematurely; and researchers who monitor trends in population, illegal activities, ecology and behaviour, as well as, health. Bwindi Impenetrable National Park has one of the best community conservation programs in the world improving coexistence between people and gorillas, contributing to the steady growth of this critically endangered mountain gorilla population” states Dr. Gladys Kalema-Zikusoka, CTPH Founder and CEO.

Mountain gorillas live in social groups and the census results indicate that the 400 mountain gorillas in Bwindi Impenetrable National Park form 36 distinct social groups and 16 solitary males. Ten of these social groups are habituated to human presence for either tourism or research and included, at the time of the census, 168 mountain gorillas or 42% of the Bwindi population.

While it was initially planned to include Sarambwe Nature Reserve in the Democratic Republic of Congo, a protected area continuous with Bwindi and therefore potential habitat for mountain gorillas, it was not possible to do so due to insecurity in the Sarambwe area at the time of the census.

The total world population of mountain gorillas now stands at a minimum of 880, representing the 400 individuals in Bwindi confirmed in this 2011 census and 480 mountain gorillas in the Virunga Massif confirmed by a census in 2010. Both populations of mountain gorillas have had positive trends in population growth over the last decade.

Conservation Through Public Health’s unique integrated approach to wildlife and community public health has helped to reduce the risks of disease transmission between people and gorillas by setting up long term systems of gorilla health monitoring; reducing infectious disease and improving hygiene and sanitation conditions of communities that surround mountain gorilla habitat, as well as, reducing household poverty and pressure on the forest habitat through community based family planning and reproductive health.

The 2011 Bwindi mountain gorilla census was conducted by the Uganda Wildlife Authority with support from l’Institut Congolais pour la Conservation de la Nature and the Rwanda Development Board. The census was also supported by the International Gorilla Conservation Programme (a coalition of the African Wildlife Foundation, Fauna & Flora International, and WWF), the Max Planck Institute for Evolutionary Anthropology, Conservation Through Public Health, the Mountain Gorilla Veterinary Project, the Institute of Tropical Forest Conservation, and the Dian Fossey Gorilla Fund International.

This census was funded by WWF-Sweden with supplemental support from Berggorilla & Regenwald Direkthilfe e.V., the Wildlife Conservation Society, and the Max Planck Institute for Evolutionary Anthropology.

Please look out for the video footage of the press conference news clips, which will be uploaded on CTPH website (www.ctph.org) soon.

Note: Gorilla censuses are conducted every four to five years to coincide with the interbirth interval of mountain gorillas. Though different census methods makes it difficult to compare population numbers from previous years, results show that the mountain gorilla population is steadily increasing, which is very encouraging for such a critically endangered species in a biodiversity hot spot with very high human population densities of 200 to 600 people per square kilometer. Please refer to the table below of all Bwindi gorilla censuses and methods used from 1997 to 2011.

 

BWINDI MOUNTAIN GORILLA POPULATION ESTIMATE

YEAR

METHOD

NUMBER

REFERENCES

1997

Single Sweep

300

McNeilage et al. 2001

2002

Single Sweep

320

McNeilage et al. 2006

2006

Single Sweep + genetic analysis

340 using single sweep and 302 after genetic analysis

Guchanski et al. 2009

2011

Two sweeps + genetic analysis

400

Robbins et al. in press

Note:

The single sweep method counts three consecutive night nests to confirm each gorilla group and can lead to an underestimate if some groups are missed out. The two sweep method helps to reduce this error.

The single sweep method can lead to an over estimate where some individual gorillas build more than one nest in one night. Genetic analysis helps to reduce this error.

REFERENCES

McNeilage, A., Plumptre, A.J., Brock-Doyle, A., Vedder, A., 2001. Bwindi Impenetrable National Park, Uganda: gorilla census 1997. Oryx 35, 39-47.

McNeilage, A, Robbins, MM, Gray, M, Olupot, W, Babaasa, D, Bitariho, R, Kasangaki, A, Rainer, H, Asuma, S, Mugiri, G, Baker, J. 2006. Census of the mountain gorilla population in Bwindi Impenetrable National Park, Uganda. Oryx 40: 419-427.

Guschanski et al. 2009. Counting elusive animals: Comparing field and genetic census of the entire mountain gorilla population of Bwindi Impenetrable National Park, Uganda. Biological Conservation 142: 290-300.

 

 

 

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