Satellite Study Reveals Critical Habitat and Corridors for World's Rarest Gorilla
New York (January 31, 2012)—Conservationists working in Central Africa to save the world's rarest gorilla have good news: the Cross River gorilla has more suitable habitat than previously thought, including vital corridors that, if protected, can help the great apes move between sites in search of mates, according to the North Carolina Zoo, the Wildlife Conservation Society, and other groups.
The newly published habitat analysis, which used a combination of satellite imagery and on-the-ground survey work, will help guide future management decisions for Cross River gorillas living in the mountainous border region between Nigeria and Cameroon.
The study appears in the online edition of the journal Oryx. The authors include: Richard A. Bergl of the North Carolina Zoo; Ymke Warren (deceased), Aaron Nicholas, Andrew Dunn, Inaoyom Imong, and Jacqueline L. Sunderland-Groves of the Wildlife Conservation Society; and John F. Oates of Hunter College, CUNY.
"We're pleased with our results, which have helped us to identify both new locations where the gorillas live and apparently unoccupied areas of potential gorilla habitat," said Dr. Bergl of the North Carolina Zoo, lead author of the study. "The study is a great example of how scientific research can be directly applied to great ape conservation."
WCS conservationist and co-author Andrew Dunn said: "The good news for Cross River gorillas is that they still have plenty of habitat in which to expand, provided that steps are taken to minimize threats to the population."
Using high-resolution satellite images, the research team mapped the distribution of forest and other land-cover types in the Cross River region. In order to ground truth the land-cover map, field researchers traveled to more than 400 control points to confirm its accuracy. They found that the land-cover rating system had an accuracy rate of 90 percent or higher. The land-cover map was combined with other environmental data to determine the extent of the Cross River gorilla's habitat. The entire Cross River region was divided into 30 x 30 meter pixels, and each pixel was rated in terms of its suitability as gorilla habitat (with steep, forested areas of low human activity receiving a high rating, and lowland areas more significantly impacted by people receiving a low rating). These ratings were translated into a habitat suitability map for the area.
With the new habitat suitability map to guide them, the team then selected 12 locations possessing all the characteristics of gorilla habitat (mainly forested landscapes far from human settlements) for field surveys. Most of these areas had no previous record of gorillas, but to their surprise, the team found signs of gorilla presence (in the form of gorilla dung and nests) in 10 of the 12 sites, thereby confirming the value of using satellite image analysis to predict suitable habitat and to prioritize areas in which to conduct further surveys.
Image credit: arenddehaas/Wikimedia Commons