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The Elusive Giant

This summer off the coast of California, whale watchers and others who venture into offshore waters are enjoying a rare treat: Blue Whales are being spotted there in record numbers. At least a hundred of these huge mammals can be found near Channel Islands National Park in Southern California, while upwards of three hundred are estimated to be spending the summer months west of San Francisco in the Cordell Banks area.

Clearly the Blue Whale is making a comeback. But don't expect next month's headlines to herald its removal from the Endangered Species List. Because even the experts can't agree on the total number of these creatures.

Blue Whales inhabit all the world's oceans. No one hunted them during the early days of the whaling industry, but technological advances like machine-powered chase boats and exploding harpoons later provided whale hunters with the means to exploit this species. Then came factory ships, which let whalers process their catch without returning to port, and the Blue Whale suffered even greater losses. In 1966, the species was protected under the Marine Mammal Protection Act, and it's assumed that its numbers have been increasing ever since.

Estimates of the worldwide Blue Whale population prior to human exploitation vary from 2,000 to 300,000. That's quite a range, and the uncertainty continues to the present day: even the most studied population, that of the North Pacific Ocean, may now number anywhere from 1,700 to 3,300, depending on who's doing the counting.

The uncertainty lies in the fact that we still haven't determined the exact number of Blue Whale populations or whether there's any exchange between them. Blue Whales usually travel alone or in pairs, which makes them difficult to locate and track despite their size. To compensate for their seemingly lonely existence, the whales use low-frequency sounds to maintain contact with their kin at ranges of up to 100 miles.

Researchers monitoring open-ocean whales use these sounds to track individual whales and study their behavior. One interesting finding is that there appear to be differences between the vocalizations made by various populations, indicating that the groups may actually be separate subspecies. Another finding: the sounds created by human activity like ship propellers and sonar may be interfering with whale communication and slowing the recovery of the species. And finally, it's been speculated that human activity is influencing ocean temperatures and that these changes could affect the abundance of krill, which Blue Whales need to survive.

Still, the increased number of Blue Whales now frequenting the waters off the West Coast is surely a good sign -- both for the whales themselves and for those of us who love to watch them.

 

 

 

 

 

2007 eNature.com