Researchers of the Whale Unit of the University of Pretoria’s Mammal Research Institute will spend the next few months researching the reasons behind the fluctuating number of southern right whales spotted this year along our coast and those of Australia and South America.
According to Dr Els Vermeulen, Research Manager at the Whale Unit, the recently completed 40th annual aerial survey revealed that only 190 females and calves (95 pairs) and 10 unaccompanied adults were spotted along the coast from Nature’s Valley to Muizenberg. Most female-calf pairs were observed in De Hoop Nature Reserve and Walker Bay.
“A total of 14 hours and 18 minutes of flying time, spread over 4 days, was required to complete the survey, which marked the second lowest number of right whales along our shores in October since 1995. After the extremely low numbers recorded in 2016 (55 pairs) this year shows a massive decrease from last year’s all-time record of 536 cow-calf pairs on the same stretch of coastline,” said Vermeulen.
“At the same time, it is also a strong decrease from the 131 cow-calf pairs that we counted in August this year between Hermanus and Infanta, only a few months ago. Reasons for this apparent shift in peak presence over the past years could be related to female right whales giving birth earlier and therefore leaving the South African breeding grounds earlier, or that female right whales are leaving too soon, possibly with a calf that is not ready to migrate. Also, the number of unaccompanied adults (males, resting females and receptive females) remain extremely low, as it has been since 2009. This tells us that non-calving right whales are still not migrating up to the South African coast as they used to do prior to 2009,” according to Vermeulen.
She said scientists still need to determine whether these trends are temporary or not. “We are busy investigating this matter, with preliminary results indicating a strong correlation with climate conditions in the Southern Ocean and fluctuations in food availability and therefore energy reserves. Similar trends are being recorded in South America and Australia, which has led to the MRI Whale Unit co-leading a research project under the auspices of the Southern Ocean Research Partnership of the International Whaling Commission.”
The objective of the research is to develop research projects to better understand how southern right whales use their foraging grounds. It is believed that a greater understanding of the links between foraging ecology and population dynamics will provide insight into the recovery and persistence of southern right whale numbers, now and in the future.
During the aerial survey all whale and dolphin species encountered were recorded, with a special focus on southern right whales. All southern right whales observed along this stretch of coastline were counted, and photographs were taken of the unique callosity pattern on the heads of all individual females with calves, as well as all individuals of a brindle grey colouration or white blaze.
Now that the survey has been completed, all photographs taken will be analysed in the coming weeks for individual identification and compared to the Whale Unit’s southern right whale photo-identification catalogue, which contains over 2 300 recognisable adults from the previous 39 annual surveys. This analysis will be done with a computer-assisted image recognition system, followed by final matching of the whales by eye.
“Through such analysis, 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 as well as their overall reproductive success, with considerable accuracy. These aspects are vital in monitoring the recovery of the South African population, which has increased at an annual rate of 6.5% since their international protection against whaling. The analysis will also allow us to investigate further possible causes and consequences of the concerning decrease in sightings along our shores in recent years,” said Vermeulen.
This year celebrates the 50th anniversary of the aerial surveys, and the 40th year of consecutive photo-identification data collection. The MRI Whale Unit invites everyone to a celebration on 24 October from 17:00 to 19:00 in the Municipal Auditorium. Prof Ken Findlay, Research Chair of Oceans Economy (CPUT) and previous head of the Whale Unit will speak on the history of whale research in South Africa and Dr Els Vermeulen, Research Manager of the Whale Unit, will provide information on the current research projects and results related to South Africa’s southern right whales. Drinks will be provided by Creation Wines. For attendance, please RSVP to firstname.lastname@example.org. For further enquiries, contact Els Vermeulen on 060 971 4301 or Chris Wilkinson (Technical Manager at the Whale Unit) on 083 580 8247.