White Shark Travels Shocking Distance
Why did the great white shark cross the Indian Ocean? It sounds like a chicken joke, but it's a genuine puzzler among shark scientists after the announcement that a female great white shark was tracked crossing and then re-crossing the Indian Ocean.
What's more, the shark, named Nicole in honor of the shark-admiring actress Nicole Kidman, made its 6,900-mile round trip in just nine months, which is faster than any known marine traveler, said Nicole's discoverers. That's some pretty efficient traveling for a shark traditionally thought of as a lifetime coastal local.
"We know very, very little about great white sharks," explained Ramón Bonfil, a shark researcher for the Wildlife Conservation Society's Marine Conservation Program. Bonfil is the lead author of a report on Nicole's remarkable journey that appears in the Oct. 7 issue of Science.
The first half of Nicole's transoceanic round trip was recorded using a 12-inch-long electronic satellite tracking device temporarily attached to Nicole's back fin. The satellite tracker provided Bonfil and his colleagues with detailed information about Nicole's 99-day journey from South Africa to Australia. Its return trip is a mystery, since by that time its tracking had broken free, as it was designed to do so it could be retrieved by researchers. The shark was only identified back in the coastal waters of South Africa by its dorsal fin, the white shark equivalent to a fingerprint.
The detailed data from Nicole's first crossing, however, raise a lot of questions about the much-hyped sharks, such as how Nicole navigated a remarkably straight course from South Africa to Australia and why she made the trip at all. Among other things, the tracking data show that Nicole spent 60 percent of its trip to Australia unusually close to the surface, within one meter of the surface, in fact.
"That leads us to believe she needed to be on the surface for a reason," said Bonfil. Perhaps the shark used some cue, like the sun or the moon, to help it navigate? No one knows. Another question: Why did it make the long trip? It wasn't for food, said Bonfil, since the waters off South Africa are amply supplied with prey. "It's an awful long trip for a meal," agreed shark researcher John Stevens for the marine sciences branch of Australia's Commonwealth Scientific and Industrial Research Organization. The next most likely reason fro a shark to cross the ocean — sex — doesn't fit either, said Stevens, since Nicole was not quite sexually mature.
And how does Nicole's trip fit into the genetic picture of white sharks? Recent genetics work on white sharks supports the idea that two separate populations reside in South Africa and Australia, with only a small amount of mixing. Was Nicole just checking out future prospects? "Now we have more questions than answers," admits Bonfil. The answers will only come with more tagging and tracking of great white sharks — something he'll do as soon as he finds more funding.
Oct 07, 2005
Larry O'Hanlon, Discovery News
Why did the great white shark cross the Indian Ocean? It sounds like a chicken joke, but it's a genuine puzzler among shark scientists after the announcement that a female great white shark was tracked crossing and then re-crossing the Indian Ocean.What's more, the shark, named Nicole in honor of the shark-admiring actress Nicole Kidman, made its 6,900-mile round trip in just nine months, which is faster than any known marine traveler, said Nicole's discoverers. That's some pretty efficient traveling for a shark traditionally thought of as a lifetime coastal local.
"We know very, very little about great white sharks," explained Ramón Bonfil, a shark researcher for the Wildlife Conservation Society's Marine Conservation Program. Bonfil is the lead author of a report on Nicole's remarkable journey that appears in the Oct. 7 issue of Science.
The first half of Nicole's transoceanic round trip was recorded using a 12-inch-long electronic satellite tracking device temporarily attached to Nicole's back fin. The satellite tracker provided Bonfil and his colleagues with detailed information about Nicole's 99-day journey from South Africa to Australia. Its return trip is a mystery, since by that time its tracking had broken free, as it was designed to do so it could be retrieved by researchers. The shark was only identified back in the coastal waters of South Africa by its dorsal fin, the white shark equivalent to a fingerprint.
The detailed data from Nicole's first crossing, however, raise a lot of questions about the much-hyped sharks, such as how Nicole navigated a remarkably straight course from South Africa to Australia and why she made the trip at all. Among other things, the tracking data show that Nicole spent 60 percent of its trip to Australia unusually close to the surface, within one meter of the surface, in fact.
"That leads us to believe she needed to be on the surface for a reason," said Bonfil. Perhaps the shark used some cue, like the sun or the moon, to help it navigate? No one knows. Another question: Why did it make the long trip? It wasn't for food, said Bonfil, since the waters off South Africa are amply supplied with prey. "It's an awful long trip for a meal," agreed shark researcher John Stevens for the marine sciences branch of Australia's Commonwealth Scientific and Industrial Research Organization. The next most likely reason fro a shark to cross the ocean — sex — doesn't fit either, said Stevens, since Nicole was not quite sexually mature.
And how does Nicole's trip fit into the genetic picture of white sharks? Recent genetics work on white sharks supports the idea that two separate populations reside in South Africa and Australia, with only a small amount of mixing. Was Nicole just checking out future prospects? "Now we have more questions than answers," admits Bonfil. The answers will only come with more tagging and tracking of great white sharks — something he'll do as soon as he finds more funding.
Oct 07, 2005
Larry O'Hanlon, Discovery News
