Mystery deaths of southern right whales

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Experts are meeting this week to try to solve the mystery of the largest ever recorded die-off of great whales.

More than 300 southern right whales, most of them young calves, have been found dead in the last five years in the waters off Argentina’s Patagonian coast – one of the most important breeding grounds for the species.

Possible causes being examined include biotoxins – naturally occurring poisons which include the venom of some snakes and spiders and the “flesh-eating” bacteria Necrotizing fasciitis – disease, environmental factors, and lack of prey, particularly the tiny krill which make up the bulk of the southern right’s diet.

Another theory put forward has been the effect of gulls, which can act like parasites, gouging skin and blubber from the whales’ backs.

The main evidence that will be examined is tests on samples taken from beached whale calves, which have shown “unusually thin” blubber, said the US-based Wildlife Conservation Society, which described the die-off as “a perplexing and urgent mystery”.

“We need to critically examine possible causes for this increase in calf mortality so we can begin to explore possible solutions,” said Marcela Uhart, one of the WCS scientists who first discovered the problem. “Finding the cause may require an expansion of monitoring activities to include the vast feeding grounds for the species.”

Southern right whales are one of three species of right whales, so called because fishermen considered them the “right whale” to hunt, because they are slow swimmers, easy to approach, live close to shore and float when dead.

In the first half of the 1800s about 45,000 right whales were killed, driving them close to extinction, before they became protected in 1937.

Since then the southern right whale