With Shark Week, the Discovery Channel’s annual paean to the ocean’s apex predators, in full swing, many of us have sharks on the brain. At Smithsonian, Megan Gambino interviewed ichthyologist George Burgess—curator of the International Shark Attack File, an archive of thousands of attacks spanning the last five centuries—about an unusual chapter of the animals’ past: Over the course of two weeks in July 1916, a great white shark attacked five people along the Jersey Shore, killing all but one. The bizarre string of attacks inspired the book, and later the film, Jaws.
Initially, however, as Burgess recounted in the interview, people didn’t even believe a shark was to blame:
The thinking was it couldn’t be a shark, because we don’t have sharks here. It must be a sea turtle. Someone suggested it was a school of turtles that was coming in and biting things. Of course, turtles don’t school, and they don’t bite human beings, but it sounded good. A killer whale was suggested as well. The theories abounded and were allowed to get out unchecked into the media simply because there was not a forceful scientific authority that really knew what was going on to step right in and try to level the conversation.
Om nom nom…oh, you caught me in the middle of dinner!
While conducting a survey of fish in an area of the Great Barrier Reef, scientists stumbled upon this little tableau: a tasselled wobbegong, or “carpet shark,” in the midst of devouring a brown-banded bamboo shark. (Either that, or they’re just sharing a very intense kiss.) The carpet shark, which hides in the sand and springs out at its prey, has never been photographed eating another shark before, though scientists could tell from poking around in their stomach contents that their distant cousins were sometimes on the menu. Carpet sharks seem to be slow eaters, though: the team hung around for a full 30 minutes to see if it would suck in more of the bamboo shark, but to no avail.
Maybe it just has stage fright.
Images courtesy of Tom Mannering and the journal Coral Reefs
Fresh shark fins drying on sidewalk in Hong Kong. Credit: cloneofsnake / flickr
On Friday, California governor Jerry Brown signed into law a bill outlawing the trade in shark fins, making it illegal for them to be imported, possessed, or distributed in the state. Chinese chefs were angered by the decision, since the fins are the prime ingredient in shark fin soup, a prized and expensive delicacy (although most Chinese voters in California support the ban… and so does retired NBA player Yao Ming). Other parts of shark meat are not highly valued, though, so most sharks caught are “finned” and thrown back into the ocean, where they slowly bleed to death. As many as 73 million sharks are killed each year, most for this purpose, and shark populations around the world are in serious decline—perhaps 30 percent of shark species are endangered.
What’s the News: Researchers found that squalamine, a steroid present in the bodies of the dogfish shark, has a protective effect against several human viruses, all of which are difficult or impossible to cure with existing drugs. The chemical has so far been shown to be relatively safe in humans and can be synthesized, suggesting it could have promise as an antiviral drug in humans.
When you’re nature’s ideal killing machine, perhaps color vision is merely an unnecessary affection. New research argues that sharks could be completely colorblind.
An Australian team led by Nathan Scott Hart investigated 17 shark species, peeking at the structure of their rod and cone photoreceptor cells in the retina. Human eyes come with red, green, and blue cone variations, allowing us to see in color. But not shark eyes. They appear to have just one kind of cone.
“Our study shows that contrast against the background, rather than color per se, may be more important for object detection by sharks,” Hart said. [CNN]
That, Hart says, may explain the common wisdom that sharks love yellow (and therefore you ought to avoid sunny swimsuits). It may be the reflective quality of yellow that catches a shark’s eye, not the hue itself.
“Bright yellow is supposed to be attractive to some sharks, presumably because it appears to the sharks as a very bright target against the water,” said Dr Hart. “So perhaps it is best to avoid those fluoro-yellow shorts next time you are in the surf.” [BBC News]
The movie was called Jaws for a reason. The great white shark’s powerful chompers make it a feared marine killing machine. However, researchers have found, it takes a while to grow into that ferociousness—adolescent great whites don’t yet have strong enough jaws to complete an attack on tougher prey without harming themselves, and it takes until adulthood for that jaw strength to develop.
The study by Toni Ferrara and colleagues, forthcoming in the Journal of Biomechanics, used the scanning technique called computerised tomography (CT) to take a look at the great white’s developing jaw, and compare it to a relative: the sand tiger shark (also called the grey nurse shark).
With these scans, they were able to create digital three-dimensional models of the sharks’ heads. The models revealed that the great white’s jaws are reinforced by layers of tough “mineralised cartilage”, which take years form. So until the sharks grow to approximately 3m [10 feet] long, they are unable to gouge chunks out of larger, tougher prey, such as sea mammals. [BBC News]
When Chrysoula Gubili from the University of Aberdeen compared the DNA of white sharks from around the world, she found a big surprise. The great white is the most genetically diverse shark studied so far but the Mediterranean fish are only distantly related to nearby populations in the North-West Atlantic, or even in South Africa. Their closest kin actually live half a world away in the Indo-Pacific waters of Australia and New Zealand….
Gubili thinks that the European population was set up by a single founding female who got lost. Female great whites undergo long migrations of thousands of kilometres, but they tend to return to the place where they were born. However, it’s possible that some individuals lose the bearings on these monster treks. These navigational problems rarely amount to anything. But if the wayward female is pregnant, she might end up setting up an entirely new splinter group in a far-off corner of the world.
Not Exactly Rocket Science: Prehistoric Great White Shark Had Strongest Bite in History
80beats: In Stereo: Hammerhead Sharks Have Human-Like Vision
80beats: The Secret Lives and Loves of Great White Sharks
Image: flickr / hermanusbackpackers
80beats aims to bring you all the science news that’s fit to turn into bytes of digital information, but sometimes DISCOVER’s other bloggers get to the juicy news stories first. To make sure you don’t miss anything, here are a couple of links:
Call it the green Nobels: Tonight in the San Francisco Opera House, six people will each receive a $150,000 Goldman Environmental Prize for their efforts to protect sharks and elephants, to promote sustainable agriculture, and to fight for other green causes.
The awards go out by region. Here in North America, the winner was Michigan’s Lynn Henning, a self-described “redneck from Michigan” who investigated huge factory farms there. Henning, 52, began testing water herself to track discharges from the farms into local waters. She has been threatened and sued and had dead animals dumped on her porch. But her tireless detective work has contributed to the state closing one factory farm and fining others more than $400,000 for 1,077 violations since 2000 [Detroit Free Press]. As Michigan’s Department of Environmental Quality suffered staff cuts, Henning’s determination kept regulators focused, former department head Steve Chester says.
South and Central America’s winner, Randall Arauz of Costa Rica, turned his attention to stopping the wasteful practice of shark finning. Arauz used a secretly recorded video to expose a ship illegally landing 30 tons of shark fins, which led to the death of an estimated 30,000 sharks. The video caused outrage in Costa Rica, which Arauz used to mobilize opposition [San Francisco Chronicle]. The Costa Rican government banned the practice, and its rules are now the model for those trying to work up international agreements against shark finning. (Worldwide restrictions were just shot down at the Convention on International Trade in Endangered Species.)
The other winners:
In Europe, Malgorzata Gorska of Poland, who stopped a highway project that would have cut through a forest.
In Asia, Sereivathana Tuy of Cambodia, who taught farmers how to ward of wandering Asian elephants rather than kill them.
In Africa, Thuli Brilliance Makama of Swaziland. This environmental lawyer won a fight for local residents to have more say in environmental decisions by the government, especially those regarding the expansions of game parks that would force people off the land.
And for island nations, Cuban Humberto Rios Labrada, who pushed for more crop diversity and less pesticide use in Cuban agriculture.
DISCOVER: Man’s Greatest Crimes Against Earth, in Pictures
80beats: Proposal to Regulate De-Finning of Sharks De-feated
80beats: Endangered Species Meeting Brings Good News for Elephants, Bad News for Coral
80beats: 9 Eco-Rules Humans Shouldn’t Break if We Want To Survive