Study: Southern Right Whales Shift Reproduction; Lack Of Food Means 1 Calf Every 4 Years, Not 3 Years
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Historically, southern right whale females would give birth to a calf every three years. They’re now calving every four years, said Claire Charlton, a lead author of the study and associate researcher at Flinders University in South Australia. The study found the extended calving interval has been evident since about 2015, with climate change identified as a primary cause because of changes melting Antarctic ice has had on ocean food webs. “This reproductive decline represents a threshold warning for the species and highlights the need for coordinated conservation efforts in the Southern Ocean, in the face of anthropogenic climate change,” the study states.
A Changing Southern Ocean
Southern right whales congregate in Antarctic and sub-Antarctic waters each year from about January to June to gorge on krill, their preferred prey. Each whale can eat more than 800 pounds of the tiny crustaceans a day. The energy they store from consuming this amount over several months is meant to sustain them during long migrations, where they won’t eat for months, back to warmer breeding grounds in Australia, South Africa or Argentina.
“These whales depend on building up fat reserves in the Southern Ocean so they can support pregnancy and nurse their calves,” said Matthew Germishuizen, a postdoctoral fellow at the Mammal Research Institute’s Whale Unit at the University of Pretoria in South Africa, who led the study’s environmental analysis. But the Southern Ocean is changing rapidly. As global temperatures rise, intensifying marine heatwaves and melting sea ice are reshaping entire marine food webs.
Krill, for instance, rely on sea ice to survive for shelter, especially as juveniles. They also feed on algae that grows beneath the ice. But in recent years, sea ice coverage in Antarctica has reached record lows. As their frozen habitat dissipates, the crustaceans are moving farther south into colder waters, or disappearing altogether from some locations, forcing their predators to travel greater distances and expend more energy while feeding.
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https://insideclimatenews.org/news/27022026/warming-ocean-southern-right-whales-fewer-calves/