How are sharks in the Gulf of Mexico eating critters from your backyard?

Game Warden Field Notes
March 6, 2015
3 mammoth bass caught in Texas lakes in one afternoon
March 9, 2015

Tiger sharks are known for their voracious appetites, so researchers aren’t surprised when a big one eats something like a manatee or a sea lion.

But woodpeckers, tanagers, yellow throats, king birds, flycatchers, doves?

A University of South Alabama scientist who has been studying Gulf of Mexico tiger sharks for 10 years said he and his colleagues have been surprised at how many backyard birds end up in sharks’ tummies.

“We know for sure that they are eating a fair amount of these birds,” said Marcus Drymon, a University of South Alabama assistant professor of marine science and researcher at Dauphin Island Sea Lab, a consortium of 22 Alabama universities.

Beyond its prevalence, researchers know little about how Gulf sharks end up eating songbirds, which has led Drymon to make a pitch for crowd-source funding on the website His goal is to raise $6,800 to pay for four satellite tagging devices known as SPOT tags.

These high-tech tags would help Drymon determine where tiger sharks are finding their bird meals.

His earlier research has included tagging sharks with $1 plastic tags that require recapture of the same animal — a fairly unlikely outcome — to be most useful, Drymon said.

Since 2006, Drymon has been studying juvenile tiger sharks, including contents of their stomachs. That can be determined by a technique called “gastric lavage,” in which researchers put a hose in the shark’s mouth and catch what comes out in a sieve, he said.

One particular shark about five years ago “coughed up a bunch of feathers,” Drymon said. When DNA analysis showed that the feathers came from terrestrial, or land-based, birds, it piqued the professor’s interest in how this could happen.

The university team catches sharks along the entire coast of Alabama, in water whose depth ranges from a few feet to more than a mile, he said. The area is within 10 to 15 miles of oil platforms, which raises the question of whether the birds are attracted to the oil platform lights, he said.

“This is the preliminary approach I’m taking, just to get baseline information to see if we can understand more about the interaction (of sharks and songbirds),” Drymon said Friday.

Recent public interest in sharks — not as something to be feared but as an important part of ocean ecosystems — has made crowd funding possible, he said.

“This is a new avenue for researchers and scientists to be able to involve the public in their research questions,” he said. “I think it’s going to be the way science moves forward. When the public can have a vested interet, I think it makes the process work best.”


Comments are closed.