Impacts of rainforest fragmentation on the composition of ground-active vertebrate communities and their patterns of seed consumption.

Abstract

Post-dispersal seed consumption by rainforest vertebrates on the forest floor can substantially influence the community dynamics of rainforest trees. Studies of rainforest vertebrate seed predators at a community level, however, are lacking. Furthermore, there is very limited understanding of the effects of forest fragmentation on seed predators and their feeding behaviour. Here, we test whether communities of vertebrate seed predators, and their patterns of feeding on rainforest tree seeds, are altered when clearing creates forest fragments in an agricultural matrix. Using infra-red trail cameras deployed at stations with and without seeds of 20 local tree species, we identified four mammal and three bird species (from 18 recorded vertebrate taxa at mainly species level) as common post-dispersal seed predators in subtropical rainforest of eastern Australia. Statistical comparisons of species-specific frequencies between six sites in continuous forest and six in small rainforest fragments (4–21 ha) showed that habitat fragmentation substantially altered species composition of seed predator communities. Two species, both small rodents, had lower abundances in fragments than in continuous forest, while higher abundances were observed in fragments for a further four species: two small birds, a medium-sized marsupial and the small non-native rodent Rattus rattus. The abundance of one larger bird species did not change. Predatory interest in seeds was also significantly affected by habitat fragmentation and generally increased in each species’ habitat of greater abundance. Collectively, seed predators showed behaviours associated with potential or actual seed consumption on an average of 43% of camera days with seeds, with about 50% of seeds physically removed or damaged after five days’ exposure. Camera data have revealed community-level changes in seed predator abundance and feeding that are likely to cause altered patterns of plant recruitment following rainforest fragmentation, but these will be complex in nature.