Tiger sharks are among the most dangerous shark species for humans. But a new study shows that songbirds are far more likely to fall victim to the predators.
Image: picture-alliance/WILDLIFE/D. Perrine
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When it comes to unprovoked attacks on humans, tiger sharks are in the same class as great whites and bull sharks.
Still, the statistical likelihood of a swimmer, surfer or diver actually getting bitten by one is rather low.
Marcus Drymon and his team took the samples directly from the stomachs of young sharksImage: Marcus Drymon
DNA from shark stomachs
To reach this conclusion, a team of reseachers around Marcus Drymond at Mississippi State University caught 105 juvenile sharks by boat in the Gulf of Mexico.
The animals were less than a meter long (three feet), meaning they had not reached adulthood. The scientists pumped the sharks' stomachs and found that 41 of them had bird remains inside, including bones and feathers. After taking the samples, the researchers released the predators back into the water unharmed.
The biologist and his team then extracted genetic information from the stomach contents and, to their surprise, found DNA traces of a large variety of bird species. They included typical land-living sparrows, swallows, pigeons and even woodpeckers, some of which also are migratory birds.
But what surprised the biologists most was that they found no traces of water birds.
"None of them were seagulls, pelicans, cormorants or any kind of marine bird," Dryman said.
The sharks don't leave the water to go hunting on land, of course. So how do they obtein their prey? It has do with the migratory routes of the birds.
The sharks were in the Gulf of Mexico during the birds' migration season. "In every instance, the timing of the tiger shark eating the bird coincided with the peak sighting for that species of bird off our coast," Drymon explains.
Kevin Feldheim, who works as researcher at Chicago's Field Museum and was a co-author of the study, adds, "The tiger sharks scavange on songbirds that have trouble flying over the ocean ... They're already worn out, and then they get tired or fall into the ocean during a storm."
The biologists found these feathers in the shark's stomachs, none of which came from marine birdsImage: Marcus Drymon
Birds that can't swim, he suggests, are probably easier for sharks to prey on than marine birds, which can handle themselves better in water.
It is known, however, that adult tiger sharks do also prey on young albatrosses.
"There's a site of Hawaii, where baby albatrosses learn to fly, and adult tiger sharks pick them off," Feldheim says.
Since Jaws, great white sharks have had a reputation for being bloodthirsty man-eaters. The Jungle Book remake shed light on threatened pangolins. Do movies help endangered animals? It depends.
Image: picture-alliance/Everett Collection
When Bambi's mom dies
In Disney's cartoon from 1942, a fawn named Bambi watches his mother die as she gets shot by a hunter. At screenings, many parents swiftly exited cinemas with crying children during the scene. According to researchers, the film had a big impact on public opinion about hunting since the villain of the movie is a hunter.
Image: picture-alliance/Everett Collection
Image of a man-eater
In the 1975 movie "Jaws", a great white shark violently attacks and kills beachgoers. The blockbuster hit created an infamous image of sharks as being bloodthirsty, vengeful predators. But this perception is inaccurate: Sharks only occasionally attack humans, and many other animals are actually far more dangerous. Experts believe "Jaws" has contributed to sharks being threatened with extinction.
Image: picture-alliance/United Archives
Orcas are killers
In the 1977 movie "Orca: The Killer Whale", a male orca seeks revenge on a captain for killing his pregnant mate. 16 years later, in "Free Willy," killer whales appear in a positive light. A foundation successfully fought for the release of the male orca portraying Willy.
Image: picture-alliance/United Archives/Impress
What's all this hype about a fish?
Pixars' cartoon "Finding Nemo" from 2003 put clown fish in the limelight. In the film, Nemo gets caught and kept in an aquarium; he has to struggle for his freedom. Although viewers sympathized with Nemo's cartoon character, the demand for pet clown fish for home aquariums subsequently rose.
Image: picture-alliance/dpa/Disney/Pixar
Cartoons highlighting conservation
The 2006 animation film "Happy Feet" draws attention to the problem of overfishing. The emperor penguin Mumble worries about the lean fishing season. Plastic garbage is also a topic: In one scene another penguin gets entangled in plastic rings of a Six Pack. The movie has a happy end: Governments around the world ban all Antarctic fishing.
Image: picture-alliance/Mary Evans Picture
Freedom for birds
The cartoon "Rio" from 2011 also has strong messages for biodiversity conservation: The last two remaining Spix’s macaws have to secure the future of their species but bandits try to smuggle the exotic birds out of the country.
The 2016 remake of the Jungle Book had an extraordinary guest, one that wasn’t included in the original: a pangolin. According to the director, employees of the Los Angeles zoo proposed the idea to include the pangolin in order to raise awareness about the threatened animal. And the media have since reported more about the plight of pangolins. Just a coincidence? Who knows.