Environmental factors influencing the distribution of southern right whales (Eubalaena australis) on the South African coast

Abstract

Distributional data from 32 years of aerial surveys of southern right whales (Eubalaena australis) along the south coast of South Africa were investigated using GIS, over a variety of spatial and temporal scales to test whether their discontinuous yet predictable distribution is related to environmental characteristics. Most whales were found in areas that provided reasonable protection from open ocean swell and seasonal winds as well as having sedimentary floors with gentle slopes, despite these characteristics being less common. Correlation type analyses with whale density only showed significance at the broadest scale. Cow-calf pairs were found significantly closer to shore and in shallower water than unaccompanied whales; they also segregated longshore in nursery areas. No relationship between reproductive success and distribution was found except a higher than expected incidence of neonatal strandings in areas dominated by unaccompanied whales. Habitat choice at this time of year was concluded to be related both to energy conservation for calves and lactating females and protection of neonates.