When a loggerhead sea turtle is hungry, he hunts for food that floats and billows in the water. What he’s after is a nice, tasty jellyfish. Unfortunately, what he sometimes finds is a discarded plastic bag that kinda looks like a nice, tasty jellyfish.
Eating one of those bags is more than unappetizing — it can be deadly.
They See It, They Eat It
Scientists recently discovered that loggerheads hunt primarily using their vision, rather than following scents or sounds, to a much greater extent than we previously knew. A team of scientists from the University of Tokyo, led by Dr. Tomoko Narazaki, set out to try to understand the foraging behavior of loggerhead turtles. Their findings were recently published in the journal PLoS ONE.
Loggerhead sea turtles are the largest hard shelled sea turtle species, with adult males growing to an average of 250 lbs. with 3 foot long shells. They are carnivores, subsisting on a diet of sea creatures, such as jellyfish, conchs, crabs, mollusks, clams, squid and the occasional fish. They can live from 30 to 50 years.
The research team discovered that loggerhead foraging can be divided into distinct phases — search, assessment, pursuit and handling of prey. As they swim, loggerheads locate their prey going by what they see.
When migrating in the open sea, loggerheads tend to eat every half hour or so, probably to keep their energy levels up. At these times, they are “opportunistic foragers.” They see what they want, they swim to it and they eat it on the move.
Loggerheads often munch on gelatinous prey like jellyfish that are floating in the water. They make a perfect, easily digestible snack. Unfortunately, the turtles’ eyes may deceive them, and they can easily mistake a plastic bag for a jellyfish.
Critter Cam Shows Researchers How Turtles Hunt
The study team figured all this out thanks to a turtle-mounted camera and 3D logger. They mounted National Geographic critter cams onto the backs of loggerhead turtles. The cameras, mounted just behind the turtles’ heads, allowed researchers to see the turtles’ food hunting behavior from the turtle’s point of view.
One of the videos captured by the critter cam shows a loggerhead swimming under the surface of the water. He sees a billowy floating mass and heads for it. It looks like a jellyfish, but by the time the turtle comes right up beside it, it becomes clear that it’s a plastic bag.
Luckily, the turtle realizes it’s not food and turns away. Had he eaten it, the bag might have become caught up in his intestines, possibly killing him. Even though he didn’t make that mistake, he’s wasted precious time and energy pursuing a piece of trash instead of the food he needs to sustain him as he swims.
Watch a BBC news clip about sea turtles and plastic bags here:
Certain populations of loggerheads are considered “endangered” under the Endangered Species Act, while other population groups are “threatened.” They are also considered “endangered” under the International Union for Conservation of Nature’s Red List.
The problem of marine debris is not easy to solve, and it’s only adding to the troubles that threaten the existence of sea turtles. Unfortunately, the abundance of plastic trash in the world’s oceans has become a distinct threat to many species that call the sea their home. This is yet another good reason to ditch plastic bags and switch to re-usable shopping bags instead.
Do it for the turtles.
Photo Credit: Thinkstock