Long-Term Dynamics of a Fragmented Rainforest Mammal Assemblage

Habitat fragmentation is a severe threat to tropical biotas, but its long-term effects are poorly understood. We evaluated longer-term changes in the abundance of larger (> 1 kg) mammals in fragmented and intact rainforest and in riparian "corridors" in tropical Queensland, with data from 190 spotlighting surveys conducted in 1986-1987 and 2000-2007. In 1986-1987 when most fragments were already 20-50 years old, mammal assemblages differed markedly between fragmented and intact forest. Most vulnerable were lemuroid ringtail possums (Hemibelideus lemuroides), followed by Lumboltz's tree-kangaroos (Dendrolagus lumholtzi) and Herbert River ringtail possums (Pseudocheirus herbertensis). Further changes were evident 20 years later. Mammal species richness feel significantly in fragments, and the abundances of 4 species, coppery brushtail possums (Trichosurus vulpecula johnstoni), green ringtail possums (Pseudochirops archeri) red-legged pademelons (Thylogale stigmatica), and tree-kangaroos, declined significantly. The most surprising finding was that the lemuroid ringtail, a strict rainforest specialist, apparently recolonized one fragment, despite a 99.98% decrease in abundance in fragments and corridors. A combination of factors, including long-term fragmentation effects, shifts in the surrounding matrix vegetation, and recurring cyclone disturbance, appear to underlie these dynamic changes in mammal assemblages.