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Toxins may have caused skewed sex ratio in killer whale calves: researcher

Image Credit: Center for Whale Research
March 26, 2016 - 6:30 PM

VANCOUVER - The high number of male babies in a group of killer whales living off the coast of British Columbia is cause for concern, researchers say.

Eight babies have been born into the Southern Resident Killer Whale population since Dec. 30, 2014, but only one of the calves has been confirmed as a female, which could spell trouble for the whales' future.

The Washington-based Center for Whale Research recently received confirmation that yet another of the baby whales is male.

"We had pretty good hints of it before, but now with some very good pictures, we know it's a male," said scientist Ken Balcomb.

The calf, known as J54, is one of five confirmed to be a male. Another is suspected to be male and the sex of the last calf is currently unknown.

The skewed sex ratio will make it difficult for the whales to reproduce when they get to breeding age, because female killer whales only give birth about once every three years.

The male whales will not breed with animals outside of their group, Balcomb said.

"Ideally, you get more or less a 50-50 ratio in the sexes," he said. "And that is true of populations that have been studied around the world, and it was true of this population when we began the study 40 years ago."

Researchers are looking at why there are so many more males in the latest baby boom.

"We're wondering if that has anything to do with the toxic environment that's affecting the fetus," Balcomb said.

Other species, such as seals, have shown similar trends when exposed to toxins, he said.

Those toxins could come from several different places, including spills, agriculture or sewage.

"Sooner or later we have a problem. And we're seeing it in the whales," Balcomb said.

More research is needed in order to find out what impact toxins are having on the whales, which could take years, he said.

The Southern Resident Killer Whale is made up of 84 killer whales living in three different pods in the Salish Sea off the south coast of B.C. and the north coast of Washington state.

News from © The Canadian Press, 2016
The Canadian Press

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