They were one of the triumphs of conservation worldwide. Grey whales were hunted to the brink of extinction in the 1850s after the discovery of calving lagoons, and again in the early 1900s with the introduction of floating whaling factories. In 1937, they were given partial protection by the International Whaling Commission (IWC), and full protection 10 years later. From then on, the eastern North Pacific grey whale started its remarkable recovery. By 1993, the population had increased to around 25,000. The following year, grey whales were the first great whales to be removed from the endangered species list.
But now scientists are worried. Grey whales, whose numbers in the eastern Pacific have fallen to around 18,000 in recent years, have been arriving at their breeding grounds off the coast of Mexico looking decidedly slender. Experts have declared that they are suffering from what they term "skinny whale syndrome". "I went down to Mexico this winter and my colleagues and I were finding whales that were starving," says Dr William Megill, whose work is funded by the Earthwatch charity. "You can tell because the fat has disappeared from the back of their heads. There are these big divots."
Nor do the whales appear to be breeding. Conception usually occurs between November and January. Grey whale females usually are pregnant over a two-year cycle, producing a single calf every other year. "It's pretty obvious when whales are breeding. The penis of a grey whale is about 9ft long and bright pink. You can't miss it. Usually when tourists come ashore in Mexico they are talking about having seen them. This year there was no talk of it, really. We have a feeling that the animals are looking for food," says Dr Megill.
In recent years, lack of food has killed thousands of grey whales. Between 1998 and 1999 an El Niño weather pattern reduced the population from around 25,000 to 18,000. It warmed up the water, which reduced oxygen levels, resulting in less of the tiny crustaceans that whales eat. "The result was that we had a lot of starving whales and it was a big enough crash in the population to have a lot of people worried," he says. Eastern Pacific grey whales eat small shrimp called amphipods, which live at the bottom of the Bering Sea. In recent years, however, they appear to have vanished. "Now, when you look there is no mud or amphipods - there's just rock. Our whole ecosystem has disappeared from that part of the Bering Sea. We don't know why the amphipod beds disappeared. It might be to do with global warming or overfishing. It might also be that the whales have finished them off. What we may be seeing is a classic predator/prey cycle."
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