Primate population decline in response to habitat loss: Borajan Reserve Forest of Assam, India

Systematic studies of the Borajan Reserve Forest in Assam, India, were conducted in 1995, 1997, and 1998. Initially this small (5 km²) forest was inhabited by substantial numbers of five species of diurnal primates and the forest was typical of Reserve Forests in northwest upper Assam. About two thirds of the forest had canopy cover of 20 – 50% or more. Civil unrest, political problems and a lack of resources for Forest Department personnel, however, resulted in rapid degradation of the area. After three years less than one third of the forest had more than 20% canopy cover; all primate populations had declined dramatically and the small percentage of juveniles in each species indicated that all were in imminent danger of local extinction. There was no evidence of hunting or trapping nor any large scale logging. Forest degradation was due primarily to small scale harvesting of forest products, selective cutting, and collection of firewood. Although only hand tools were employed, the forest inexorably declined in response to these steady pressures. Borajan may be an object lesson as to what can happen but it need not be the harbinger of Assam’s future.     

Factors influencing the decline of a Bonelli's eagle Hieraaetus fasciatus population in southeastern Spain: demography, habitat or competition?

We investigated three possible causes of territory desertion among Bonelli's eagles Hieraaetus fasciatus in Murcia (southeastern Spain): low demographic parameters, low habitat quality and competition with Golden eagles Aquila chrysaetos. From 1983 to 1997, we surveyed a Bonelli's eagle population. Abandoned and occupied territories were compared to find differences in demographic parameters (flight rate, productivity and mortality) or habitat characteristics. Mortality was significantly higher in abandoned territories. Abandoned territories also had larger areas of forest and extensive agriculture, while occupied territories had more shrublands. Competition with Golden eagles was not a determinant of territorial abandonement but interacted with human persecution of the species. Management implications are discussed.