Sir Peter Scott Fund project: Dolphins, Africa
Marine mammals are apex predators that play a central role in the dynamics of marine communities through predation, resource facilitation, trophic cascades and behavioural influences such as competition and risk effects. Their association with high biodiversity and a greater sensitivity to ecosystem changes such as pollution and habitat alteration make them natural indicator species for the health of an ecosystem.
The Benguela ecosystem, off the south-west coast of Africa has undergone radical changes in the last three decades due to a combination of overfishing and natural environmental variability. Although many of the top predators in the Benguela ecosystem (such as birds and seals) have been relatively well studied, the delphinid component of the ecosystem, dominated by Heaviside's (Cephalorhynchus heavisidii) and Dusky Dolphins (Lagenorhynchus obscurus), has received very little attention, and the effect of ecosystem changes on these species is not known.
We are using a variety of research methods including acoustics, visual surveys, individual identification and molecular work. Static acoustic monitoring involves mooring hydrophones to the seabed in key dolphin habitats where they provide data on habitat use and acoustic behaviour of dolphins 24 hours a day for extended periods. They also give us a unique insight into the real 24-hour patterns of habitat use and how these correlate with human impacts such as boat traffic and construction in key habitats. Our analyses of stable isotopes of carbon, nitrogen and sulphur in skin samples will show us variation in diets between study sites and seasons. Combined with information about prey and competitor abundance, social parameters such as group size and behaviour, and broad-scale environmental variables, will allow us to better understand and predict changes in behaviour and distribution patterns in this dynamic marine environment.