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Wednesday, December 3, 2014

Grey seals identified as killers behind mystery harbour porpoise deaths » Focusing on Wildlife

Grey seals identified as killers behind mystery harbour porpoise deaths » Focusing on Wildlife


“This is a new behaviour. They’re normally
fish eaters, they can eat a large fish, around half a metre. It’s a switch from
fish-eating to mammal-eating. I don’t think it’s indicative of lower fish
stocks, they just learned a new trick,” Mardisk F Leopold, who led the
research, told the Guardian.
“They are very social and when they go
hunting, they do it alone, so it was surprising they can transfer this
behaviour to others. It’s not just one seal. This is everywhere along the Dutch
coast.”
He said there was no reason to think the
behaviour, which took off in a big way from 2006 onwards, would not be replicated
by other seals in northern Europe. “We know
there is exchange between ‘Dutch’ seals and ‘English’ or ‘Scottish’ seals, so
there’s ample opportunity for dispersal of this behaviour.”
The porpoises are targeted by the seals
for their blubber, with healthy and fat juvenile the favoured prey. The
scientists speculate as to whether porpoises will adapt to the threat of being
eaten by seals by becoming leaner and faster swimmers, though this would put
them at risk of dying from emaciation, another major cause of their death.
The paper concludes that many of the
porpoises were found on beaches used by swimmers and surfers and there was no
evidence to suggest why “humans may not be at risk from grey seal attacks.”


Leopold said there had been reports of
seal-human incidents in northern Europe, but
no deaths. “Attacks is maybe a big word – people have been bitten while
swimming. I don’t think there have been attacks that have not been provoked.”

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