Small mammal community succession on the beach of Dongting Lake,China after the Three Gorges Project

Although the Three Gorges Project(TGP)may have affected the population structure and distribution of plant and animal communities,few studies have analyzed the effect of this project on small mammal communities.Therefore,the present paper compares the small mammal communities inhabiting the beaches of Dongting Lake using field investigations spanning a 20-year period,both before and after the TGP was implemented.Snap traps were used throughout the census.The results indicate that the TGP caused major changes to the structure of the small mammal community at a lake downstream of the dam.First,species abundance on the beaches in­creased after the project commenced.The striped field mouse(Apodemus agrarius)and the Norway rat(Rat­tus norvegicus),which rarely inhabited the beach before the TGP,became abundant(with marked population growth)once water was impounded by the Three Gorges Reservoir.Second,dominant species concentration in­dices exhibited a stepwise decline,indicating that the community structure changed from a single dominant spe­cies to a more diverse species mix after TGP implementation.Third,the regulation of water discharge release by the TGP might have caused an increase in the species diversity of the animal community on the beaches.A sig­nificant difference in diversity indices was obtained before and after the TGP operation.Similarity indices also indicate a gradual increase in species numbers.Hence,a long-term project should be established to monitor the population fluctuations of the Yangtze vole(Microtus fortis),the striped field mouse and the Norway rat to safe­guard against population outbreaks(similar to the Yangtze vole outbreak in 2007),which could cause crop dam­age to adjacent farmland,in addition to documenting the succession process of the small mammal community inhabiting the beaches of Dongting Lake.