Population Size & Growth Rates

Population Size & Growth Rates

Conservation efforts have led to an apparent increase in overall population of the mountain gorilla (Gorilla beringei beringei) in the Virunga and at Bwindi. The overall population is now believed to be approximately 790 individuals, with 4 of them being in care of the Senkwekwe Centre orphanage in the DR of Congo.

In December 2010 the official website of Virunga National Park announced that “the number of mountain gorillas living in the tri-national forested area of which Virunga forms a part, has increased by 26.3% over the last seven years – an average growth rate of 3.7% per annum.” The 2010 census estimated that 480 mountain gorillas inhabited the region. The 2003 census had estimated the Virunga gorilla population to be 380 individuals; which represented a 17 % increase in the total population since 1989 when there were 320 individuals. The population has almost doubled since its nadir in 1981, when a census estimated that only 254 gorillas remained.

The 2006 census at Bwindi indicated a population of 340 gorillas, representing a 6% increase in total population size since 2002 and a 12% increase from 320 individuals in 1997. All of those estimates were based on traditional census methods using dung samples collected at night nests. Conversely, genetic analyses of the entire population during the 2006 census indicated there were only approximately 300 individuals in Bwindi. The discrepancy highlights the difficulty in using imprecise census data to estimate population growth.

In both Bwindi and the Virunga, groups of gorillas that were habituated for research and ecotourism have higher growth rates than un-habituated gorillas, according to computer modeling of their population dynamics. Habituation means that through repeated, neutral contact with humans, gorillas exhibit normal behavior when people are in close proximity. Habituated gorillas are more closely guarded by field staff and they receive veterinary treatment for snares, respiratory disease, and other life-threatening conditions. Nonetheless, researchers recommended that some gorillas remain un-habituated as a bet-hedging strategy against the risk of human pathogens being transmitted throughout the population.

In Uganda, Gorilla tracking permits cost US$500 person with the intention that a portion of the fee goes to the park and gorilla conservation initiatives, helping to ensure the gorilla survival. The fee is worth this genuine once-in-a-lifetime opportunity as only about 720 mountain gorillas remain in total worldwide. Despite their recent population growth, the mountain gorilla remains threatened. Mountain gorillas (Gorilla beringei beringei) are listed as Endangered on the IUCN Red List. Endangered means the maximum population reduction over a three-generation (i.e. 60-year) period from the 1970s to 2030 is suspected to exceed 50%, hence qualifying this species for Endangered under criterion A4.

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