Posted on September 25, 2018
The Whale Unit of the University of Pretoria’s Mammal Research Institute (MRI) will be conducting their annual aerial survey of southern right whales from 1 October through to mid-October. Having commenced in 1979, this is the 39th consecutive annual survey and the resulting dataset is one of the longest running datasets on any marine mammal worldwide.
The survey is flown annually between Nature’s Valley and Muizenberg at an altitude of approximately 300m and within 1km of shore using an Airbus H120B helicopter. Flying is usually only carried out under adequate survey / weather conditions between 08h00 and 16h00 as light and glare outside of these times compromises survey photography. During the survey, all encountered whale species will be recorded, but special focus will be given to encounters of southern right whales. As such, all southern right whale females with calves, as well as all individuals with distinctive brindle colouration or markings, will be photographed in order to allow individual identification. Vertical images of both the heads and the backs of the animals will be taken, which will allow recognition of the pattern formed by the wart-like callosities on their heads, and in some cases of the white and grey pigmentation patterns on their backs. Photography of each group usually takes less than five minutes, during which time the helicopter decreases in altitude to hover some 150-200m above the whales. Once sufficient photographs are obtained, the helicopter returns to the 300m altitude to continue searching for whales, 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 photographs and associated data will be analysed. The best images of each individual will be selected from each encounter and compared to all other selected images from the 2018 survey as well as to the Whale Unit’s catalogue of identification photographs of just over 2300 recognisable adults from the previous 38 annual surveys. Sorting of images is initially done using a computer-assisted image recognition system, followed by final matching of the whales by eye. These analyses allow for sighting histories of known individuals to be compiled and a subsequent investigation of individual movement and distribution patterns as well as the reproductive / calving histories of females. These data will then be used to further investigate 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 has her first calf), which allows researchers to accurately model the population demographic parameters over the long term.
This year´s survey is particularly interesting due to the much larger number of southern right whales visiting our shores. Preliminary count surveys have indicated the presence of nearly 700 female southern right whales with calves between Hermanus and Witsand. This is nearly double the amount expected under normal conditions! However, sightings of these animals haven’t been normal in the last couple of years. Sightings decreased dramatically in 2015, 2016 and 2017, and this year seem to be at an all-time high since aerial surveys began in 1979. The exact reason for this is currently under investigation, but it is believed to be related to limiting feeding conditions in the Southern Ocean, and an associated change in calving intervals. Similar trends have been observed in the breeding grounds of Argentina & Brazil, as well as in Australia.
Southern right whales received their name from the historic whalers who believed them to be the “right whale” to hunt, as they are were predictable in distribution, generally slow swimming, and most importantly float when killed. Indeed, the species was heavily whaled in the past (particularly by the Moby Dick style foreign open-boat whaling fleets between about 1780 and 1835), and it reduced the global population from an estimated 70,000 - 80,000 individuals to a mere 60 reproductive females at the termination of right whaling in 1935. However, since their international protection in 1935, the three breeding populations (in coastal waters of Australia, Argentina and South Africa) have been increasing at about 6.5% per annum. Currently, the regional (southern African) abundance is estimated just over 6,000 individuals, with a global population size of just under 15,000 individuals. Thus, one of the main objectives of the annual aerial survey is to monitor this remarkable recovery!
The MRI Whale Unit’s 2018 survey is being flown in association with Silvercross Aviation and is generously funded by Cape Nature. It will be run with the support of the Dyer Island Conservation Trust, De Hoop Collection, Denel Overberg Test Range, and private citizens along the route. The survey is carried out under a permit from the Department of Environmental Affairs to approach whales and under specific Marine Protected Area permits from the relevant conservation authorities. Weather plays an important part in achieving the full survey coverage and flying will be required over weekends.
Also you can help and stay closely up-to-date on the status of our southern right whales! In celebration of this year´s all-time record of whales along our shores, we are launching an adopt-a-whale programme, in which everyone join our community by symbolically adopting a whale, this way supporting whale research and conservation in South Africa. All raised funds go integrally to cover the costs of our fieldwork. For more information, please check www.adoptawhale.co.za
For further enquiries please contact Dr Els Vermeulen (Research Manager at the Whale Unit ) on 060 9714301or Chris Wilkinson (Technical Manager at the Whale Unit) on 083 580 8247
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