Stream Amphibian Detectability and Habitat Associations in a Reduced Impact Logging Concession in Malaysian Borneo

Abstract

Borneo's amphibians face an uncertain future due to high levels of forest degradation and a paucity of data for effective conservation management. Several studies identified strong species–habitat relationships in pristine and conventionally logged forests. However, these studies did not account for detectability or habitat associations in sustainably managed forest reserves. Here, we determined detectability and species habitat relationships in stream amphibians within the Deramakot forest reserve, a reduced impact logging concession in the Malaysian state of Sabah, northern Borneo. We analyzed data for 10 stream species collected along 32 stream transects. An occupancy modeling framework was used to determine the climatological, temporal, and environmental covariates associated with detection and occupancy probabilities. We identified high variability in detection probability between species, including significant associations with moon phase (six species), time since sunset (five species), humidity (five species), rainfall (four species), and temperature (three species). Stream slope and volume provided by far the best predictors of occurrence, with significant positive or negative associations with the occupancy of six species each. These associations were more similar to those found in pristine compared with conventionally logged habitats. The highly variable detectability associations within our amphibian community suggest a level of temporal separation in regard to activity and breeding phenology in these species. This stresses the importance of accounting for detection probability via surveying sites across varying climatic/temporal conditions to obtain a representative sample of amphibian communities in pristine and disturbed tropical forests.