Its a right bumper year for our whales!
The number of southern right whales spotted along our shores has increased substantially compared to last year.
The 38th annual aerial survey for southern right whales, conducted by the Whale Unit of the University of Pretoria’s Mammal Research Unit, counted a total of 527 southern right whales between Nature’s Valley and Lamberts Bay. This included 366 females and calves (183 pairs) and 161 unaccompanied adults.
The 2016 count comprised a total of only 119 southern right whales, including females, calves and unaccompanied adults. The 2017 count was conducted over eight days between 2 and 10 October, during which operations were only halted for one day due to unfavourable weather conditions. The survey was completed in a total flying time of 29 hours and 30 minutes using an Airbus ECl 20B under charter from Silvercoss Helicopters.
Most of the female-calf pairs were observed in the De Hoop Nature Reserve and the area between Cape Agulhas and Gansbaai, whereas most unaccompanied adults were observed within Walker Bay.
“Although the numbers of southern right whales along our shore this year are not as high as have been observed in previous years, they are substantially higher than the mere 119 southern right whales (including all females, calves and unaccompanied adults) observed in 2016, thus showing a clear increase in presence,” says Dr Els Ver-meulen, research manager at the Whale Unit.
All the whale and dolphin species encountered during the survey were recorded, with a special focus on southern right whales. Photographs were taken of the unique callosity pattern on the heads of all individual females with calves as well as all brindle-grey coloured individuals.
A total of 6 800 photographs were taken and these will be analysed in the coming months for individual identification and compared to the Whale Unit’s southern right whale photo-identification catalogue, which contains nearly 1 900 recognisable adults from the previous 3/ annual surveys. This analysis is done first with a computer-assisted image recognition system, followed by final matching of the whales by eye.
Such analyses, says Els, assist in the investigation of individual distribution and movement patterns as well as the reproductive success of females with considerable accuracy. The data assists in monitoring the increase of the South African population of right whales, which was previously estimated at a rate of 7% per year over the survey period. The increase is believed to result from the international protection of the population since 1935.
The analyses will also allow for the investigation of possible causes and consequences of the concerning decrease in sightings along parts of South Africa’s shores in recent years, and the increased presence recorded this year.
The MRI Whale Unit’s 2017 survey was funded by the International Whaling Commission, and conducted with the assistance of the Dyer Island Conservation Trust. Support was given by De Hoop Collection, Denel Overberg Test Range, Cape Nature and private citizens. The survey was 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.
For further information, contact the Whale Unit’s Dr ElsVer-meulen (research manager) on 0609714301 or Chris Wilkinson (technical manager) on 083 580 8247.