Print PageThe niche concept is important in almost every level of ecological organizations, from individual behaviors to ecosystem functioning. However, the position and width of the niche in many species can be adjusted in response to changes in resource, competition, and predation. This increases the difficulties in studying niches. Recently, stable isotopes have been proposed as a tool that can effectively quantify niches. In this study, we tested the ability of stable carbon and nitrogen isotopes to detect inter- and intra-specific niche differences in diets of three small mammal species in an evergreen forest in Taiwan. The three species are known to have distinct trophic roles: Apodemus semotus is omnivorous, Eothenomys melanogaster herbivorous, and Episoriculus fumidus insectivorous. In addition to inter-specific niche differences, we also investigated intra-specific (i.e. inter-sex) niche differences for two of the species with appropriate sample sizes.
Results/Conclusions
Our results suggest that there were significant overall differences in diet niches among the three species, as reflected in stable isotope values of their hair samples. Stable nitrogen isotopes in particular, can clearly distinguish among E. fumidus, A. semotus, and E. melanogaster, with a pattern that is expected based on their known trophic roles. Using the coefficient of variation for stable isotope values as an indicator of diet niche width, we found that carbon sources were more varied for omnivorous A. semotus than for insectivorous E. fumidus. Furthermore, A. semotus also showed differences in stable carbon isotope values between males and females. This study provided evidence that stable isotopes could be an effective tool to test niche differentiations and overlaps among forest-dwelling small mammals.
