Lowland Gorilla Population Numbers Questioned
Concerns Expressed About Counting Methods Used in Recent Survey
Oct 29, 2008
In August of 2008 the Wildlife Conservation Society announced the results of their latest census of lowland gorillas (Gorilla gorilla gorilla) in the Republic of Congo stating that 125,000 gorillas had been counted in two parts of the country. Prior to the survey the estimated population of lowland gorillas throughout their range was less than 100,000 animals.
Threats to Wild Gorillas
The western lowland gorillas, one of the great ape species, are presently listed as Critically Endangered. Commercial logging and the resultant increase in access to deep forest leads to increases in the bushmeat trade. Logging also contributes to habitat loss, as does the increasing human population, which needs land for cultivation and wood for housing, heating and cooking.
Disease has more recently been recognized as an important issue in the survival of gorillas. These primates are related closely enough to humans to be susceptible to Ebola virus and HIV/AIDS. The Ebola virus has been linked with the decline in the overall gorilla population.
The Lowland Gorilla Study in Republic of Congo
The Wildlife Conservation Society census was conducted over 18,000 square miles in the forests of the Republic of Congo. These dense forests with abundant supplies of the types of herbs and other greens favored as food by the lowland gorillas may provide the level of protection from human contact that the species needs to survive.
The Cautions Expressed Regarding the Gorilla Population Study
But concerns have been expressed about methodology of the study. Gorillas make nests to sleep in at night, staying far above the forest floor and safer from predators. The problem is whether there is enough known about gorilla nest use.
How often do the gorillas reuse nests? How many gorillas share a nest at night? If gorillas generally build a new nest each night and live for even twenty years, that is a large number of nests per gorilla. Was there a measure developed to determine the age of the nests or how recently they had been used?
These questions will need to be answered before there is complete acceptance of the data and before the new population estimates are used for determining the status of the species.
In the meantime, even the researchers involved in the study caution that the increased numbers do not guarantee survival for the species. Many of the nests were found outside of protected areas. Gorillas using these nests are more vulnerable to the bushmeat trade and habitat loss than those deep within protected forests.
If the population is as dense as is suggested by the survey, this group of lowland gorillas would be particularly vulnerable to disease outbreaks. Ebola virus or HIV/AIDs could sweep through and decimate their numbers.
Whether the population is 50,000 or more than double that, the threats to the species remain. Protection of habitat and monitoring changes in habitat use continue to be needed for all the great apes.
 |
