Does resource availability govern vertical stratification of small mammals in an Australian lowland tropical rainforest?

Abstract

Mammal assemblages of rainforest communities are commonly vertically stratified. This can be associated with competition for, or access to, resources in the upper canopy layers of the forest. This study investigated the extent of vertical stratification in a small mammal community of a tropical rainforest and whether any structure was related to resource abundance. The mammal community was vertically stratified, with 'Pogonomys mollipilosus' and 'Cercartetus caudatus' found only in the upper canopy layers and 'Rattus' sp., 'Isoodon macrourus' and 'Antechinus flavipes rubeculus' on the ground and in the understorey layer. 'Melomys cervinipes' and 'Uromys caudimaculatus' were found at all four height layers. Total rodent captures were not significantly correlated with the abundance of fruit and flower resources, but arboreal captures of 'M. cervinipes' and 'P. mollipilosus' were correlated with the number of individual canopy trees of four prominent flower- and fruit-yielding species: 'Syzigium sayeri', 'Acmena graveolens', 'Argyrodendron perelatum' and 'Castanospermum australe'. We suggest that arboreal behaviour in these rodents serves to provide the advantages of first access to food resources, the availability of abundant resources in the canopy, and, ultimately, reduced competition in the upper strata.