Why Are Dolphins Dying?

May 19, 2018

Mercury….

Why Are Dolphins Dying?

In a white-tiled lab at London Zoo, just across the street from the giraffes, two investigators are slowly and painstakingly dissecting a porpoise.

Rescue workers recovered the stranded animal on a beach in Somerset a week before. It was maimed by brutal red gashes – from a boat’s propeller, they thought.

Investigators Rob Deaville and Matt Perkins are not so sure. Over the next two hours, they will try to uncover what killed this particular porpoise. They will also look for clues to a much bigger puzzle, one that involves all of marine life, answering questions like: what is the state of our oceans? What are the biggest threats? And what can we as humans do to help?

Deaville and Perkins conduct post-mortems on more than a hundred porpoises, dolphins and whales a year for the Zoological Society of London. Their work has uncovered surprising threats, from long-banned chemicals lingering in the water to the devastating impact of fishing nets. But it has also revealed good news about the power of policy change and the return of endangered species.

“We use a dead body on a beach to shed light on its life, not just its death,” says Deaville, who leads the UK’s Cetacean Strandings Investigation Programme – or CSIP for short – at the Zoological Society.

Cetaceans are dolphins, porpoises and whales, and the UK’s waters host an incredible range of them. About a quarter of the world’s known species have been found here, from bus-sized, singing humpback whales, to sleek, leaping bottlenose dolphins.

Some 600 cetaceans wash up on UK shores every year. CSI scientists have systematically examined 4,000 of the strandings since 1990, more recently adding large sharks to their remit to deepen our understanding of sea life.

In the lab, surrounded by intriguing jars labelled “penguin” and “mountain chicken”, Deaville and Perkins are taking a closer look at this particular porpoise’s wounds. The tools they use are basic – a scalpel, tweezers, a pair of garden shears – but having seen hundreds of bodies, they quickly form a view of how the porpoise died.

The injuries are too shallow for propeller damage; pecking seagulls are probably to blame. Deaville gently slices off a strip of skin and blubber to be tested later for accumulated chemicals. A putrid, rotten smell rises from the body. I realise now why I was asked before the post-mortem if I had a strong stomach, and warned that some observers faint.

“As we’ll go through this, you’ll see a lot of similarities between us and them, because they are mammals,” Deaville says as he lifts out the dark purple liver. “But you’ll see differences as well.”

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