Southern Right Whale – 2021 Aerial Survey for South Africa

Southern Right Whale - 2021 Aerial Survey for South Africa

Southern Right Whale - 2021 South Africa Aerial Survey Team

Between the 3rd and 5th of October 2021, the University of Pretoria’s Mammal Research Institute Whale Unit conducted the 42nd annual aerial survey to monitor the South African population of southern right whales.

This survey was flown from Nature’s Valley to Muizenberg, using an Airbus EC120B under charter from Silvercoss Helicopters. All southern right whales observed were counted, and photographs taken of the unique callosity pattern on the heads of all females with calves, and all individuals with a brindle, grey or white blaze colouration.

Approximately seventeen hours were flown in total, spread over a 3-day period during which 382 females and calves (191 pairs) were counted and photographed, as well as 32 adult whales without a calf (so-called ‘unaccompanied adults’), bringing the total to 414 southern right whales between Nature’s Valley and Muizenberg. The vast majority of female-calf pairs were observed between De Hoop Nature Reserve and Walker Bay.

As can be seen in the graph below, this number is higher than the numbers recorded in 2019 and 2020, but still remains well below what we would expect under ‘normal conditions’. The number of ‘unaccompanied adults’ (males, resting females and receptive females) continues to remain extremely low, as it has been since 2009, indicating that non-calving right whales are still not migrating to the South African coast as they used to.

In mid-September, just prior to this aerial survey, 418 females with calves (209 pairs) were counted between Hermanus and Witsand on one of our supplementary gyrocopter surveys.

This total is slightly higher than the above helicopter survey, confirming that female southern right whales continue to limit their residency time in the South African breeding area, with possible negative effects on the chances of calf survival i.e. calves are having to leave our sheltered waters earlier than normal in order to undertake their first migration southwards with their mother.

Southern right whales are known to be “capital breeders”, which means they rely heavily on their foraging success and stored energy supplies to support their reproduction and migration. Their body condition (or “fatness”) is thus extremely important to ensure successful pregnancy and calf rearing.

However, recent research has shown that right whale mothers have decreased in body condition by 24% since the late 1980s, indicating clearly that their feeding is less successful. We strongly believe this lack of energy reserves lies at the basis of the increased calving interval (from 3 to 4) and a reduced migration towards our shores of the non-calving individuals.

Now that the survey has been completed, all photographs taken will be analysed in the coming weeks for identification of individual whales, which is then compared to the Whale Unit’s national southern right whale photo-identification catalogue which contains over 2,400 recognisable adults from the previous 41 annual surveys. This analysis will be done with a computer-assisted image recognition system, followed by final confirmation and matching of the whales by eye.

Through such analyses, we will be able to determine which females calved this year, how long it took them to produce a new calf, their individual distribution and movement patterns and, with considerable accuracy, assess their overall reproductive success.

These aspects are vital to monitor the recovery of the South African population of right whales, which has been increasing at a rate of 6.5% per year since international protection of the population against whaling. These analyses will also allow us to investigate further possible causes and consequences of the concerning decrease in sightings along our shores in recent years.

The MRI Whale Unit wishes to thank all those who continue to support the survey, such as Silvercross Helicopters, De Hoop Collection, Denel Overberg Test Range and private citizens along the route. The survey was carried out under a permit from the Department of Forestry, Fisheries and the Environment to approach whales and under specific Marine Protected Area permits from the relevant conservation authorities. We also wish to thank fellow whale researcher, Dr Gwen Penry, for the warm welcome when we flew over Plettenberg Bay main beach (see photograph attached).

Should you wish to support this very important research and conservation programme, and stay up-to-date on the status of our southern right whale research, please contact us to find out more about our exciting and informative adoption programme. Symbolic whale adoptions make unique and exciting gifts, and are an authentic opportunity for corporate environmental responsibility. All funds raised in this way directly support our fieldwork.

You can also follow our activities through our FB page https://web.facebook.com/MRIWhaleUnit

For further enquiries please contact Dr Els Vermeulen (Research Manager at the Whale Unit) on els.vermeulen@up.ac.za or 060 9714301 or Chris Wilkinson (Technical Manager at the Whale Unit) on 083 580 8247