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UP assesses the health of southern right whales in aerial survey as study marks 50 years

Posted on October 08, 2019

The Whale Unit of the University of Pretoria’s (UP) Mammal Research Institute (MRI) is conducting its annual aerial survey of southern right whales to establish the health of the whale population. The survey, which began on 30 September, is expected to be completed mid-October

According to Dr Els Vermeulen, Research Manager at the MRI Whale Unit, the survey is flown annually between Nature’s Valley and Muizenberg at an altitude of approximately 300m and within 1km of shore using an Airbus H120B helicopter.

“During the survey, all encountered whale species will be recorded, but special focus will be given to encounters of southern right whales. All southern right whale females with calves as well as all individuals with distinctive brindle colouration or markings will be photographed in order to allow individual identification,” she said.

Dr Vermeulen explained that despite a large number of southern right whale calves present on the Cape’s shores last year, this year numbers appear to be low again. “A preliminary survey was conducted in mid-August, indicating the presence of 131 females with calves and 26 unaccompanied adults, leading to a total of 288 southern right whales between Hawston and Witsand. This is considerably less than last year when over 700 calves were counted, and less than expected.”

Sightings of southern right whales in their breeding ground have not been at normal levels in the last few years. Within South Africa, sightings of females with calves decreased dramatically in 2015, 2016 and 2017 and increased to above-normal levels in 2018. Sightings of unaccompanied adults (males and non-calving females) decreased drastically in 2010 and have not yet returned to normal levels.

She said the exact reason for these enormous fluctuations in numbers is under investigation. “Preliminary data strongly suggest that whales might not be finding enough food in their feeding grounds of the Southern Ocean to sustain the energy cost of migration and reproduction. Female right whales are now giving birth on average every four years instead of three years, thereby reducing the rate at which the population is increasing.”

Dr Els Vermeulen

To this end, the MRI Whale Unit is investigating the whales’ nutritional condition using overhead drone images, as well as the effect of climate change on the productivity of their feeding grounds. Similar trends have been observed in the breeding grounds of Argentina and Brazil, as well as in Australia. It is a concerning situation because if climate change lies at the heart of this problem, it might not easily be solvable. Also, southern right whales are a species still recovering from the whaling days, when their population was hunted to near extinction. Today, the global population is only at 30% of its original numbers and still needs plenty of time to recover.

Southern right whales received their name from the historic whalers who believed them to be the “right whale” to hunt, as they are predictable in distribution, generally slow swimming and, most importantly, float when killed. 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 this 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 at just over 6 000 individuals, with a global population size of just under 15 000 individuals. “One of the main objectives of the annual aerial survey is to monitor this recovery and the new challenges these whales face,” said Dr Vermeulen.

Data collected from all whale sightings will be used to investigate the vital parameters of the population, including abundance estimation, population growth rate, survival, calving intervals, and age at first parturition (age at when a female has her first calf), which allows researchers to accurately model the population demographic parameters over the long term.

During the survey, vertical images of both the heads and the backs of the southern right whales will be taken, which will allow recognition of the pattern formed by the wart-like callosities on their heads and, in some cases, of the white and grey pigmentation patterns on their backs. Photography of each group usually takes less than five minutes, during which time the helicopter decreases its altitude to hover some 150-200m above the whales. Once sufficient photographs are obtained, the helicopter returns to 300m altitude to continue searching for whales, although in areas of high whale densities the aircraft may move directly from group to group at the lower altitude.

After the survey, the collected photographs and associated data are analysed. The best images of each individual will be selected from each encounter and compared to all other selected images from the 2019 survey as well as to the Whale Unit’s catalogue of identification photographs of just over 2 300 recognisable adults from the previous 39 annual surveys, explained Dr Vermeulen.

“Sorting of images is initially done using a computer-assisted image recognition system, followed by final matching of the whales by eye. These analyses allow for sighting histories of known individuals to be compiled and a subsequent investigation of individual movement and distribution patterns as well as the reproductive / calving histories of females,” she explained.

The MRI Whale Unit’s 2019 survey will be flown in association with Silvercross Aviation with the support of the De Hoop Collection, Denel Overberg Test Range and private citizens along the route.

“This year celebrates the 50th anniversary of the aerial surveys, and the 40th year of consecutive photo-identification data collection. It is therefore one of the longest running datasets on any marine mammal worldwide,” said Dr Vermeulen.

The MRI Whale Unit invites the public to its anniversary celebration on 24 October 2019 between 17:00 and 19:00 in the municipal auditorium of Hermanus. Guest speakers include Director of the UP Mammal Research Institute Professor Andre Ganswindt, who will give the welcome address. Professor Ken Findlay, former head of the MRI Whale Unit, will speak on the history of whale research in South Africa, and Dr Vermeulen will provide information on the current research projects and results related to South Africa’s southern right whales.

Dr Vermeulen encouraged members of the public to also support the southern right whale research through the adopt-a-whale programme “in which everyone can join our community by symbolically adopting a whale.”

“By doing so you will be supporting whale research and conservation in South Africa. All funds raised go to cover the costs of our fieldwork,” she said. For more information, go to www.adoptawhale.co.za

Published by Hlengiwe Mnguni

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