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Dolphins suffer in extreme weather


Study finds decrease in numbers in coastal dolphins battling El Niño and heavy rain. Andrew Masterson reports.


Bottle nose dolphins are at risk from climatic events.
Bottle nose dolphins are at risk from climatic events.
Getty Images/Gabriel Barathieu

Severe weather events can disrupt coastal dolphin populations – and even potentially lead to the death of some of the animals – a study has found.

A paper in the journal Global Change Biology reports on the fates of a dolphin community affected by the 2009 El Niño event combined with a decrease in sea surface temperature and above-average rainfall.

Researchers found that the group, usually resident in coastal waters off the Western Australian town of Bunbury, experienced a sharp drop in numbers.

Lead researcher, Kate Sprogis of the Cetacean Research Unit of Australia’s Murdoch University, found the outcome was the result of a combination of factors that led to extreme weather conditions.

Sprogis and her colleagues have studied the Bunbury dolphin community extensively since 2007. They found that their numbers went into “sharp decline” during the El Niño event – an outcome they linked to the concurrent weakening of the predominant coastal ocean driver, the Leeuwen Current.

“Bottlenose dolphins in Bunbury are selective feeders and their abundance in coastal waters is likely linked to the abundance and distribution of their preferred prey,” Sprogis says.

“We believe that dolphins moved away from the area in search of an adequate food supply and, of those that stayed in the area of changing conditions, many found it harder to locate their preferred prey.”

The researchers note in their paper that several studies exist examine the effects of climate events on peak predators in deep ocean ecosystems – but this is the first tracking the effects of those events on peak species living closer to shore.

Don’t miss our profile of dolphin expert Kate Sprogis, published on Friday, October 13.

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Andrew Masterson is news editor of Cosmos.
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