Rodent community structure in tropical forests in south Vietnam: comparative ecology of two dominant species and implications for conservation.

Rodents were sampled using the capture-mark-recapture technique along transects in disturbed and undisturbed tropical forest in Cat Tien National Park in south Vietnam. The transects comprised two strata: traps were placed on the ground and in the canopy 2-12 m above the ground. At the main transect, which was 1500 m long and located in undisturbed forest, a total of 438 rodents (173 squirrels and 265 murids) of 12 different species (one Scuridae sp.; 11 Muridae spp.) were marked between January 2005 and January 2006. At this study site and at another undisturbed tropical forest site in the same area, two species dominated: the rat Maxomys surifer (Miller, 1900) and the squirrel Callosciurus flavimanus (Geoffroy, 1831). During the study period we observed no significant difference between the average abundances of the two species (4.67 ± 0.86 and 3.1 ± 0.85 individuals per 100 trap nights, respectively) or between the average proportions of resident squirrels and rats (60.0 ± 24.1 and 62.5 ± 11.5, respectively). The number of squirrels that were permanent residents (i.e. dwelling in the same habitat for 1 year) was eightfold the number of rats that were permanent residents. In addition, there was some synchrony in the daily capture dynamics of squirrels and of rats. We observed no significant difference in the total abundance of small mammals between the arboreal and ground strata. At two disturbed tropical forest sites in the same area, however, no such balance between squirrels and rats was observed, and the density of C. flavimanus was very low. We suggest that the relationship between these two dominant species can act as an indicator of the integrity of tropical forest ecosystems in south Vietnam.