Effects of tropical rainforest roads on small mammals: fragmentation, edge effects and traffic disturbance

In north-eastern Queensland, impacts on small mammals of traffic disturbance were compared with those caused by physical presence of rainforest roads by trapping in the rainforest interior and adjacent to narrow, unsealed roads with traffic volumes of 264+/-71 or 4.2+/-1 vehicles per day. Of the three small mammal species that were most commonly trapped, the proportion and abundance of native Rattus sp. increased at higher-traffic and decreased at lower-traffic sites; the abundance of Melomys cervinipes was relatively constant at both traffic treatments and in the forest interior, and Uromys caudimaculatus decreased at higher-traffic treatments. Road crossings by the smaller rodents, Rattus sp. and M. cervinipes, were primarily influenced by the presence of the road, rather than increased levels of traffic, as crossings were significantly inhibited at both traffic treatments compared with the forest-interior control and there was no difference between traffic levels. Crossings by the larger, more mobile U. caudimaculatus were unaffected by road presence or traffic level. Therefore, increased traffic volume did not appear to affect small mammal movements or community structure. However, since higher traffic levels were not constant throughout the peak periods for activity of these nocturnal species, further investigations are required to determine whether constant nocturnal traffic disturbance may further restrict road crossings by small mammals and alter community structure adjacent to roads.