Established in 1985 by the late Prof. Peter B. Best, the Mammal Research Institute Whale Unit of the University of Pretoria researches the ecology, population dynamics and behaviour of cetaceans (whales, dolphins and porpoises) in Southern African waters, with the principal objective of providing information that will promote their conservation.
Our flagship project relates to the population monitoring of southern right whales which breed along the southern Cape coast.
Monitoring the South African population of southern right whales
We have been monitoring the South African population of southern right whales since 1979 through a series of annual photo-identification aerial surveys. This survey is conducted each year in October during which all female southern right whales with calves between Nature’s Valley and Muizenberg are counted and photographed. This 40 year of standardised survey series is one of the longest continuous data sets for any marine mammal in the world, making it an extremely valuable dataset that is of national and inter-national importance.
Using the photographs of the whale´s unique callosity pattern, we are able to identify each individual female, allowing us to follow them over time. Through this method called “photo-identification”, we are able to derive the main population parameters, such as age of first calving, calving interval (how often the same female has a calf), calf survival rates, number of calving females, total population size and population trend over time.
Based on these surveys, it was estimated that the South African population of southern right whales contains 6,116 individuals and is currently increasing at a rate of 6.5% per year.
Southern right whales as indicator species
Due to its annual migration from their feeding grounds in the Southern Ocean to the coast of South Africa, and the availability of a unique 40-year long dataset, the southern right whale seems to be the “right sentinel” to assess, from mainland Africa, the health condition of a wide region in the Southern Ocean while monitoring the population dynamics of these whales.
By understanding the important link between nutritional status (based on recent prey availability and body condition) and reproduction, the trend in breeding success of the South African population of southern right whales can provide a measure of the changing system health throughout their feeding grounds across a wide region of the Sub Antarctic and Antarctic Southern Ocean south of South Africa.
Therefore, we are investigate long-term correlations between the apparent decreased reproductive success in the South African southern right whale population (as seen by fluctuating numbers of southern right whales along our shores) and indices of oceanographic variability in their contemporary feeding areas, and assess whether these in turn coincide with measures of body condition and nutritional stress in parous females. Ultimately, this study anticipates to predict the effects of climate change on the population recovery of this depleted krill-dependent species.
In order to achieve this, boat-based fieldwork is being carried out through which we obtain skin and blubber samples for isotopic and endocrinologic research. At the same time, drones are being used to obtain overhead photographs of the full body length of individual right whales which allows us to quantify their body (and thus nutritional) condition.