Researchers pumped the stomachs of baby tiger sharks to find out what they eat. Photo by Field Museum
May 22 (UPI) -- To better understand the diets of baby tiger sharks, scientists have been catching young shark specimens and making them throw up. Analysis of DNA in the shark vomit showed baby tiger sharks consume songbirds.
Tiger sharks are known as the garbage bins of the ocean. When it comes to eating, they're rather indiscriminate. Researchers have previously found evidence that tiger sharks eat seabirds, but scientists were surprised to discover the DNA of backyard bird species -- the genetic signatures of sparrows, woodpeckers and doves -- in the barf of baby sharks.
"Tiger sharks will see an easy meal and snatch it up, but I was surprised to learn that the sharks were eating songbirds -- I assumed that they'd be seabirds," Kevin Feldheim, a researcher at Chicago's Field Museum, said in a news release. "It was one of the coolest projects I've been associated with using DNA to tell a story."
For the study, scientists pumped the stomachs of 105 baby tiger sharks. The stomach contents of 41 sharks featured bird remains. But half-digested birds aren't easy to identify, so scientists sent the remains to the lab for DNA testing.
The test results, published this week in the journal The Scientific Naturalist, showed the baby tiger sharks regularly eat backyard bird species.
"None of them were seagulls, pelicans, cormorants, or any kind of marine bird," said Marcus Drymon of Mississippi State University. "They were all terrestrial birds."
In Hawaii, adult tiger sharks have been documented picking off juvenile albatrosses learning to fly. Authors of the latest study estimate the baby sharks targeted tired or injured birds migrating across the Gulf of Mexico.
"The tiger sharks scavenge on songbirds that have trouble flying over the ocean," said Field Museum researcher Kevin Feldheim. "During migration, they're already worn out, and then they get tired or fall into the ocean during a storm."
The population numbers of most shark species have declined over the last few decades. By better understanding the behaviors of vulnerable shark species, scientists can potentially improve conservation strategies.