Mousedeer densities in a tropical rainforest: the impact of selective logging.
The responses of two frugivorous ungulates, the mousedeer species Tragulus javanicus klossi and T. napu borneanus, to mechanized selective logging in Sabah, Malaysian northern Borneo were investigated from June 1992 to December 1993. Densities of Tragulus spp. were measured in forest logged 2, 5 and 12 yr previously, and in primary forest, by line-transect surveying. Environmental variables thought to influence mousedeer densities were measured to examine the causes of any observed variation. Both Tragulus spp. were less common in logged forest, with the larger T. napu exhibiting the most marked decline. Differences in the density ratio of the 2 species between primary and logged forest were consistent with predictions related to fasting endurance and body size. Mousedeer densities were negatively correlated with the proportion of severely disturbed forest, and positively correlated with the availability of potential food resources. Densities of T. javanicus were correlated with the abundance of small fruits, which is consistent with diet records, whilst T. napu densities, and overall mousedeer biomass were correlated with the density of large strangling Ficus trees, which are considered a keystone food resource for many tropical frugivores. This observation emphasizes the importance of Ficus in maintaining frugivore communities and has corresponding implications for forest and conservation management. Mousedeer appear to be more adversely affected by selective logging than other frugivorous ungulates or primates within the same forest. This may reflect limitations in the dietary flexibility of mousedeer imposed by the effects of a small body mass on energetic requirements and digestive capabilities. The need for a highly nutritious and readily digestible diet is assumed to restrict their ability to utilize browse as an alternative to fruit.