Southern right whale Aerial Survey - Press Release 2020

Unfortunately, this year the numbers of southern right whales along our shores appear to be very low again.

A preliminary count survey conducted at the end of August indicated the presence of 71 females with calves and 11 unaccompanied adults, leading to a total of 153 southern right whales, between Hermanus and Witsand.

This is about half of what was seen last year around the same time, and likely to become the second lowest count in over 30 years. Current information from other breeding grounds, including Australia and Brazil, also indicate a dramatic decreased presence of southern right whales this year.

As we all know, sightings of southern right whales in their breeding grounds haven’t been normal in the past decade. Within South Africa, sightings of females with calves decreased dramatically in 2015, 2016 and 2017, increased above normal-levels in 2018 and dropped again substantially in 2019. Sightings of unaccompanied adults (males and non-calving females) have decreased drastically in 2010 and have not yet returned to normal levels. This suggests that only pregnant females, which are about to give birth, complete their migration to the South Africa coast to increase their calf’s survival chances, whereas the others are not undertaking their migration to the full extent. Additionally, data continues to show a decreased calving success, with females giving birth to a calf every 4 to 5 years instead of every 3 years. Successful calving in southern right whales relies on having an adequate body condition (blubber thickness or “fatness”), which is directly influenced by their feeding “success”. Because of this, our working hypothesis is that a decreased availability of food in the southern right whale feeding grounds in the Southern Ocean lies at the heart of these changes.

And indeed, new results of our ongoing work show that the South African southern right whale population has drastically changed their feeding locations in the past two decades, suggesting that their previously productive feeding grounds have changed over time. Considering the vast oceanic range of the southern right whale feeding grounds, our recent findings point toward large-scale ecosystem changes in the Southern Ocean. The observed limited migratory behaviour and decreased calving success of southern right whales in South Africa further indicate that while these changes in feeding behaviour may be an attempt to keep up with a changing ocean, they may in fact not be sufficient for the whales to obtain an adequate body condition which will ensure their calving success. In this regard, we are further investigating the whales’ nutritional condition using overhead drone images and analysis of blubber stress hormone levels. These results should be available at the end of this year.

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 recovery and the new challenges these whales face.

The MRI Whale Unit’s 2020 survey will be flown in association with Silvercross Aviation. It will be run with the support of the 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 Environment, Forestry and Fisheries 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.

Stay closely up-to-date on the status of our southern right whale research through our adopt-a-whale programme, in which everyone can 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