The Mammal Research Institute of the University of Pretoria will start flying their 36th annual helicopter survey of the Southern Cape’s right whale population on 29 September this year; a survey that will be generously sponsored by four offshore oil and gas companies namely; ExxonMobil Exploration and Production South Africa Limited, Impact Africa Limited, The Petroleum Oil And Gas Corporation of South Africa (SOC) Ltd, and Thombo Petroleum Limited.
This survey will be flown coastwise in a Bell Jet Ranger helicopter at an altitude of 305m some 500 to 800m offshore between Nature’s Valley and Muizenberg over the following two to three weeks. All encountered whale species will be recorded and all groups of southern right whales comprising a cow and calf pair or animals with distinctive brindle colouration markings will be photographed. Vertical images of both the heads and the backs of the animals allow individual identification, as individual whales can be recognised from the patterns of the wart - like callosities on their heads and in some cases from the pigmentation patterns on their backs. Photography of each group usually takes less than five minutes, during which time the helicopter descends to and hovers some 150m above the whales, before continuing the survey at 305m, although in areas of high whale densities the aircraft may move directly from group to group at the lower altitude.
After the survey, the collected identification photographs are filtered to select the best images of each encountered individual and these are compared to the Institute’s catalogue of identification photographs from previous surveys. Sorting of images is initially done using a computer-based image recognition system, followed by final matching of whales by eye. The catalogue now has some 1700 recognisable adults on file from the 35 previous surveys and over 2900 re-sightings of individuals (some have obviously been re-sighted multiple times!) have been recorded. This process allows for the movements and distributions of individuals to be investigated and the reproductive / calving histories of individuals to be analysed. These analyses provide a suite of information on the vital parameters of the population including abundance estimation, population growth rate, survival, calving intervals and age at first parturition (age at when a female calf first returns with her calf) which are used to model the population for comparison with and verification of the raw survey counts.
Southern right whales were subject to severe historical whaling pressure (particularly from the “Moby Dick style”, open-boat whalers between 1780 and 1835). By the time of international protection in 1935 the global population has been estimated to have been reduced from between some 70,000 and 80,000 individuals to probably less than a few hundred. Despite such protection, illegal Soviet whaling fleets continued to take southern right whales up until the 1960s. With the local population increasing at about 7 percent per annum and now in the region of 5,000 to 6,000 individuals (of a total global population of some 15,000 individuals), southern right whales appear to staging a strong recovery. The annual survey provides us with important conservation data with which to monitor this recovery. All surveying is carried out under a permit from the Department of Environmental Affairs to approach and disturb whales and under specific Marine Protected Area permits from conservation authorities. Weather plays an important part in achieving the full survey coverage and flying may be required over weekends.