The 41st annual Aerial Survey of Southern Right whales by the Whale Unit of the University of Pretoria’s Mammal Research Institute (MRI) is set to begin on 28 September through to mid-October. The main objective of the survey is to monitor the recovery and population growth of these whales since their international protection in 1935 after being heavily whaled between 1780 and 1835, reducing the global population from 80 000-70 000 to about 60 reproductive females when Right whaling was terminated in 1935.
The survey is conducted by an airbus H120B helicopter between Nature’s Valley and Muizenberg, with all encountered whale species recorded. However, special attention is given to Southern Right whales with calves and individuals with distinctive brindle colouration or markings. Carrying out the survey requires pristine weather conditions, between 08:00-16:00, to evade potential glare that could hinder the survey photography undertaken.
Analysis of the data in the form of photos is used for comparison and identification of individuals that were sighted during the previous 40 annual surveys. The acquired data is used for further investigation and to compile population parameters and demographics of Southern Right whales, such as population growth rate, survival rate, calving intervals, and the age at which a female whale has her first calf.
A preliminary count survey conducted at the end of August revealed a decrease in sightings of these whales with a total of 153, consisting of 71 calving females and 11 unaccompanied adults. The sightings of calving females has not been frequent for the past decade and has had a drastic decline between 2015 to 2017, as well as in 2019. However, the total number of adult males and non-calving females is far less than females with calves. This suggests that only pregnant females complete their migration to South African coasts. The changes in whale migration can be attributed to the changes in the ecosystems of the feeding and breeding locations. Longer calving intervals may point to insufficient nutrition that does not allow adequate body conditions for reproduction and increasing survival rate.
The survey is administered under a permit from the Department of Environment, Forestry and Fisheries, and from relevant conservation authorities. People can join in the project by symbolically adopting a whale. The funding generated through this is used to cover this field work. More information can be found on www.adoptawhale.co.za and on https://web.facebook.com/MRIWhaleUnit
Illustration: Marchall Potgieter