Calving season for the critically endangered North Atlantic right whale has come to a close with 23 new baby whales, the most calves born in a single year since 2009.
Part of the baby boom during the winter calving season can be attributed to females giving birth at closer intervals than in years past: 18 of this year’s moms gave birth within the last six years.
“While a healthy right whale can give birth every three to four years, we had been seeing nearly 10 years between calves for some females,” Amy Warren, scientific program officer with the New England Aquarium’s Anderson Cabot Center, said in a statement.
One explanation for the calving delay is the stress of climate change, researchers say. Small crustaceans called copepods, the main food source for baleen whales, including North Atlantic right whales, have started shifting locations over the last decade, and many whales are traveling farther to find sufficient food.
There are an estimated 384 North Atlantic right whales (Eubalaena glacialis) today, living along the East Coast of North America. At least one whale was spotted near Ireland, and many are turning up in Canada’s Gulf of St. Lawrence, over a thousand kilometers from their usual habitat. Swimming to the Gulf makes their 1,600-kilometer (1,000-mile) migration from Florida to New England roughly 50% longer. That equates to more energy put into finding food, potentially leaving less resources for raising babies, Philip Hamilton, a senior research scientist with the New England Aquarium, told Mongabay in an email.
Still, the closer birth interval suggests that “those females have been more successful at foraging and are in better condition,” Hamilton told Mongabay by email. He added that this year’s high calf numbers are also partly due to a “backlog of calving females” after several years of delayed births.
An increase in births is welcome news for the species, though scientists estimate that a sustained 50 births per year are needed to restore the population. That’s a tall order for a species with just 70 reproductively active females.
Right whales were so named because they float when killed, making them the “right” whale for commercial whalers. They’re also slow going, coastal, and spend most of their time near the surface, qualities that made them easy prey for whale hunters and still put them in danger today.
Their migration takes them through busy shipping lanes and patches of ocean dense with ropes and trap lines. The U.S. National Oceanic and Atmospheric Administration estimates more than 85% of the whales have been entangled with fishing gear at least once in their lives.
So far, this year’s calves appear to be doing well. “At last count … 18 of the 23 calves had successfully migrated to the feeding grounds around Massachusetts,” Hamilton said. At this point in 2024, at least five of the 20 known calves had already died, he added.
Banner image: A North Atlantic right whale with her calf. Image by FWC Fish and Wildlife Research Institute via Flickr (CC BY-NC-ND 2.0).
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