Just two years ago we were celebrating that mountain gorilla populations were increasing especially in Uganda. However, a recent study has just poured water on these findings and suggests that that nest counting methods overestimate the number of gorillas.
Some gorillas construct more than one nest per night
According to to research conducted in the Bwindi Impenetrable Forest, Uganda, mountain gorilla populations may have actually declined. Researchers estimate gorilla numbers by counting the number of ‘nests’ which the animals build each night. This method suggests that there are 336 gorillas left in this population accounting for half of the worlds mountain gorillas. However, recent DNA tests from dung were conducted by Katerina Guschanski of the Max Planck Institute for Evolutionary Anthropology in Liepzig, Germany, and reveal that there are actually far fewer mountain gorillas. She found evidence of 302 separate genetic codes or individual gorillas, suggesting that the nest counting method overestimates the population size because some gorillas create more than one nest. The study was reported in the New Scientist magazine. A previous genetic study put the population at 340 individuals. Dr. Guschanski’s work suggests that this population has declined by 10% and while some news reports are saying mountain gorillas are in dire sraits, scientists are more cautious and are not really sure if the populations are decreasing, or stable.
Many forget that mountain gorillas have always been restricted to montane forest habitats which are found in a very small part of Africa on the tops of mountains. Although it is unlikely that populations were ever much greater than they are today due to habitat restrictions, it is of concern that they are threatened by habitat exploitation, poaching and disease caused by greater contact with humans. Climate warming however may be one of the greatest threats which will accelerate all the other impacts. Temperature incraeses have already melted many of the glaciers on the East African mountains, and as this continues it will cause mountain gorilla habitat to recede up the mountains.
The Virunga population of mountain gorillas was estimated to number about 380 individuals in 2007 (up from 260 in 1978). These figures are considered accuate because they are based actual sightings. We are awaiting for the outcome of an ongoing gorilla census in the Virunga National park, so far nothing alarming has been reported.
If it is true that the Bwindi population is shrinking, then this is bad news for mountain gorillas – it is estimated that there are only around 700 in existence, this work suggests at least a 5% decline of the global population.
Mountain gorilla deaths in the last 18 months have been reported on a number of blogs
10 were killed allegedly by rangers in 2007
7 died of natural causes in Rwanda
3 Eastern lowland gorillas in Congo have also died
1 died in a tragic accident in Mt. Tshiaberimu
2 died of disease in Mt Tshiaberimu
Gorilla doctors in DR Congo, Uganda and Rwanda are working hard to monitor gorilla health and treat any injuiries or sicknesses. Read Dr.Lucy Spelmans blog for more details.