New research in SA that southern right whales off its coast are getting thinner, having fewer calves and leaving these breeding grounds sooner provides further evidence for research conducted in the Americas that climate change shifts in the Southern Ocean could cause population decline.
Dr Els Vermeulen, research manager at the University of Pretoria’s (UP) whale unit, said: “Southern right whales are a sentinel species and, if climate change is affecting them, it is undoubtedly affecting other smaller species. They are an iconic animal and important to our country.”
Among the threats to the whales’ population, which was increasing until about 10 years ago, is ocean warming, which can harm their food supply, including krill.
International research, published last October, found whales may not only be affected by climate change, but may help to mitigate it.
“(Whales) may play a role in mitigating climate change and supporting the Antarctic krill (Euphausia superba) population, a keystone prey species that sustains the entire Southern Ocean (SO) ecosystem,” reported the authors from the Federal University of Santa Catarina in Brazil and the University of Utah, US.
This research was based on a five-decade (1971 to 2017) data series of individual southern right whales, photo-identified at the Península Valdés in Argentina.
“We found a marked increase in whale mortality rates following El Niño events. By modelling how the population responds to changes in the frequency and intensity of El Niño events, we found that such events are likely to impede SWR population recovery and could even cause population decline,” the scientists warned.
Vermeulen said of the SA findings: “Recent research has shown that right whale mothers have decreased in body condition by 24% since the late 1980s, indicating clearly that their feeding is less successful.”
It is not unique to our country. They have seen the same in the Australian population and the Americas, but not to the same degree.
— Dr Els Vermeulen, UP whale unit manager
“Body condition”, or fatness, is crucial to successful pregnancies and calf rearing among these whales, which depend on foraging and stored energy supplies to achieve this, she said.
“Since commercial whaling stopped, the recovery of the southern right whale population was a great conservation success story. But now the science is telling us that these marine mammals are coming under renewed pressure from a more modern problem, likely linked to climate change,” she added.
The number of unaccompanied adults (males, resting and “receptive” females) visiting SA has dropped noticeably since 2009, showing that non-calving whales are also migrating in lower numbers to these shores compared with the previous decade.
Vermeulen, who runs the second-biggest right whale research project in the world and one of the longest-running, said of this concern: “It is not unique to our country. They have seen the same in the Australian population and the Americas, but not to the same degree.”
The whale unit’s research project started in 1969 and falls within UP’s Mammal Institute. The WWF-SA (World Wide Fund for Nature-SA) last week announced a partnership with the unit to help fund the data set of global value.
“The impact of changes in the Southern Ocean is a large global issue,” said Vermeulen, noting that changes in the right whale population migrating to SA shed light on larger environmental problems. “This shows how important long-term monitoring is.”
Craig Smith, WWF’s senior manager: marine programme, said supporting their research would promote the protection of an iconic species which was vital to SA’s coastal tourism industry.
“There is no doubt we are experiencing major changes in our oceans as a result of climate change, which in turn could have severe implications for marine species and livelihoods,” he said.
When commercial whaling in the US was reaching its peak, hunting was the biggest threat to (sperm whale) Moby Dick and other species of whales.
But since the 1982 moratorium on commercial whaling (which Japan and Norway did not join) the harpoon and modern weapons are no longer the worst danger to this endangered species — six out of the 13 great whale species are classified as endangered or vulnerable, according to WWF.
Instead, man’s land activities are compromising the whales in the Southern Ocean.
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