Ecological consequences of the Three Gorges Dam: insularization affects foraging behavior and dynamics of rodent populations

A number of permanent and seasonal islands will be formed when the world's largest darn, China's Three Gorges Dam, begins to operate at full capacity in 2009. The possible effects of this large-scale habitat insularization on biodiversity and ecosystem processes have attracted considerable attention from scientists around the globe. We investigated the species composition and distribution of rodent populations at two geographic locations in the Three Gorges Reservoir Area through field surveys and determined the dietary composition of dominant rodent species using stable isotope techniques. Our results show that the total rodent density on the islands was significantly higher than that of mainland areas. Stable isotope analysis revealed that the dietary composition of rodents was more diverse on islands than at nearby mainland sites. Moreover, the island populations had greater overlap in food sources than did the mainland populations, suggesting more intense competition for food in the newly insularized habitats. Thus, habitat fragmentation due to the construction of the Three Gorges Dam may substantially increase intra- and interspecific competition among local rodent populations, leading to further changes in species composition and biodiversity.