Ensemble modelling of southern Australian bottlenose dolphin Tursiops sp. distribution reveals important habitats and their potential ecological function

Modelling dolphin distribution is key for understanding their ecology and for their conservation and management. Information on the distribution and preferred habitats of southern Australian bottlenose dolphins Tursiops sp. is lacking, particularly in metropolitan areas where the species is under threat from anthropogenic activities. Here, we used boat-based surveys and an ensemble modelling approach that combined results from 6 modelling techniques (generalised additive models, generalised boosted models, classification tree analysis, flexible discriminant analysis, random forest and maximum entropy) to identify areas of high probability of southern Australian bottlenose dolphin occurrence along the metropolitan coast of Adelaide, South Australia. We used kernel density estimation to identify core and representative areas according to behaviour and investigated the importance and potential ecological function of areas of high dolphin occurrence. The ensemble predictions of dolphin distribution performed better than the corresponding single models. Results indicate that depth, benthic habitat type and slope influenced dolphin occurrence along Adelaide's coast. Dolphins favoured shallow nearshore areas and temperate reefs in summer, shallow nearshore areas in autumn and deep waters further offshore in winter. In comparison to other observed behaviours, core feeding areas overlapped considerably with areas of high probability of dolphin occurrence. Thus, we suggest that prey availability is an important driver influencing the seasonal variation in dolphin distribution along Adelaide's metropolitan coast. Our predictions identify priority areas for dolphin conservation and for the implementation of boating and fishing regulations. Continued monitoring is needed to assess potential changes in preferred habitat under increasing anthropogenic pressures.