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Remote sensing analysis reveals habitat, dispersal corridors and expanded distribution for the Critically Endangered Cross River gorilla Gorilla gorilla diehli

Richard A. Bergla1 c1, Ymke Warrena2, Aaron Nicholasa2, Andrew Dunna3, Inaoyom Imonga3, Jacqueline L. Sunderland-Grovesa2 p1 and John F. Oatesa4

a1 North Carolina Zoological Park, Asheboro, North Carolina, USA.

a2 Wildlife Conservation Society, Takamanda–Mone Landscape Project, South West Region, Limbe, Cameroon

a3 Wildlife Conservation Society–Nigeria, Calabar, Nigeria

a4 Department of Anthropology, Hunter College CUNY, New York, USA

Abstract

Habitat loss and fragmentation are among the major threats to wildlife populations in tropical forests. Loss of habitat reduces the carrying capacity of the landscape and fragmentation disrupts biological processes and exposes wildlife populations to the effects of small population size, such as reduction of genetic diversity and increased impact of demographic stochasticity. The Critically Endangered Cross River gorilla Gorilla gorilla diehli is threatened in particular by habitat disturbance because its population is small and it lives in an area where high human population density results in intense exploitation of natural resources. We used remotely-sensed data to assess the extent and distribution of gorilla habitat in the Cross River region and delineated potential dispersal corridors. Our analysis revealed > 8,000 km2 of tropical forest in the study region, 2,500 km2 of which is in or adjacent to areas occupied by gorillas. We surveyed 12 areas of forest identified as potential gorilla habitat, 10 of which yielded new records of gorillas. The new records expand the known range of the Cross River gorilla by > 50%, and support genetic analyses that suggest greater connectivity of the population than previously assumed. These findings demonstrate that considerable connected forest habitat remains and that the area could potentially support a much larger gorilla population if anthropogenic pressures such as hunting could be reduced.

(Received August 27 2010)

(Reviewed December 14 2010)

(Accepted December 22 2010)

(Online publication November 01 2011)

Correspondence:

c1 North Carolina Zoological Park, Asheboro, North Carolina, USA. E-mail richard.bergl@nczoo.org

p1 Current address: Center for International Forestry Research, Bogor, Indonesia

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