Southern Right Whale Annual Aerial Survey

October 11, 2013 by dyertrust

The Mammal Research Institute Whale Unit of the University of Pretoria will be able to do their annual helicopter survey of the southern right whale population over the first two to three weeks of October. This survey, to be carried out westwards from Natures Valley to Muizenberg, is the 35th in a series of surveys that have been carried out annually since 1979. The survey is flown some 500 to 800 m offshore and all encountered southern right whales and other whale species are recorded. Groups of southern right whales comprising a cow and calf pair are photographed with images of both the heads and the backs of the animals being taken, as individuals 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. Identification photography of such groups usually takes less than five minutes per group during which the helicopter hovers some 500ft above the whales.


After the survey the collected identification photographs are filtered to select the best images of each encountered individual and these are compared to the Whale Units catalogue of identification photographs from previous surveys. Comparisons are initially done using a computer based image recognition system, which is followed by matching by eye. The Whale Unit now has some 1200 recognisable individuals on file and over 2200 re-sightings of individuals (some individuals have obviously been re-sighted multiple times!) have been recorded, allowing 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, growth, 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. With the local population now increasing at about 7 percent per annum and now in the region of 5,000 individuals, local 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 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 need to be carried out over weekends.

The Dyer Island Conservation Trust is an avid supporter of the Mammal Research Institutes Whale Unit and the annual helicopter Whale survey, helping them on a logistical basis wherever possible.

Further information about this project may be obtained from Ken Findlay or Meredith Thornton of the MRI Whale Unit on 0825708212 or 0827465579 respectively. This project is sponsored by PetroSA.