“We have been fortunate that on every whale watching trip we have seen whales. In addition there are sharks, penguins, seals and an abundance of seabirds thrown into the deal,” says Wilfred Chivel of the Dyer Island Conservation Trust and whale and shark watching companies, Dyer Island Cruises and Marine Dynamics.
This follows the publication last week of the findings of the 41st annual aerial survey done by the Whale Unit of the University of Pretoria’s Mammal Research Institute. The survey found that it has been a slow season in as far as our visiting sea mammals are concerned.
The 2020 survey, which monitors the South African population of southern right whales, was conducted under the watchful eye of Dr Els Vermeulen, Research Manager at the Whale Unit based in Hermanus, between 27 and 29 September.
All southern right whales observed along the stretch of coastline between Nature’s Valley and Muizenberg 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.
A total of 12 hours and 52 minutes of flying time, spread over 3 days, was required to complete the survey, using an Airbus EC120B under charter from Silvercross Helicopters. In total, 136 females and calves (68 pairs) of southern right whales were counted and photographed, as well as 29 adult whales without a calf (so-called ‘unaccompanied adults’), bringing the total to 165 southern right whales between Nature’s Valley and Muizenberg. Most female-calf pairs were observed in De Hoop Nature Reserve and Walker Bay.
“Although these numbers mark the second-lowest number of right whales along our shores in October in the past 32 years, we must remember that the population of southern right whales is increasing annually by 6.5%,” says Vermeulen.
“So while we are seeing fewer whales, their world-wide numbers are increasing. In 2018 a large number of whales were counted along our shores with many females mating. The gestation period is three years, so we can make an educated guess that there will be an increase in whale numbers in our area over the next couple of years.”
It has been found that females return to where they were born to calve, hence the return visits every year.
Despite the lower counted numbers there are still numerous sightings reported every day via social media. The Overberg Whale and Dolphin Group was started on WhatsApp to assist in alerting residents and visitors to sightings. To join the group simply send a message with your name and number to 082 746 5579 .
According to Vermeulen, this year’s number is also slightly lower than the 142 females with calves (71 pairs) counted at the end of August of this year between Hermanus and Witsand, re-indicating female southern right whales continue to limit their residency time in the South African breeding ground, with possible negative effects on the chances of calf survival.
The number of ‘unaccompanied adults’ (males, resting females and receptive females) also remained 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 do before 2009.
Findings point to changes in the Southern Ocean
“In general, successful calving and migration in southern right whales rely on having an adequate body condition (blubber thickness or ‘fatness’), and thus energy reserves, which is directly influenced by their feeding ‘success’. It is therefore believed that a decrease in their feeding success lies at the heart of these anomalous trends.
“As our research continues, this hypothesis is being confirmed by our scientific data, which indicate strong correlations between the southern right whale prevalence along our shores with climate conditions in the Southern Ocean and fluctuations in food availability. In fact, new data reveal that the South African southern right whales have drastically changed their feeding locations in the past two decades, suggesting that their previously productive feeding grounds have changed over time,” says Vermeulen.
These findings point toward large-scale ecosystem changes in the Southern Ocean, likely impacting several different oceanic top predators. Data further indicate that while this shift in foraging locations may be an attempt to keep up with a changing ocean, the changes may not be sufficient to ensure an adequate body condition is obtained, negatively impacting the success of their calving and migration.
“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,” she says.
Very similar trends are being recorded in South America and Australia, resulting in the MRI Whale Unit co-leading the Southern Right Whale research theme under the Southern Ocean Research Partnership of the International Whaling Commission.
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 40 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 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, increasing at a rate of 6.5% per year, since the international protection of the population against whaling. The analyses will also allow us to investigate further possible causes and consequences of the concerning decrease in sightings along our shores in recent years.”
Stay updated on the status of our southern right whale research through the adopt-a-whale programme, in which everyone can join the 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 fieldwork. For more information, please check www.adoptawhale.co.za. You can also follow our activities through our Facebook page at MRIWhaleUnit,” says Vermeulen.
For further enquiries please contact Dr Els Vermeulen (Research Manager at the Whale Unit) on 060 9714301 or Chris Wilkinson (Technical Manager at the Whale Unit) on 083 580 8247.
It was also reported that nurdles, small plastic pellets about the size of a lentil that are used to make nearly all plastic products, have resurfaced in our area. According to marine expert Meredith Thronton, more than 7 kg was collected at Cape Infanta on Monday. She says nurdles that have been dumped in the ocean make their way from the substrate onto our shores as the winter swells shift sand on the beaches.