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.

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