Scientists left giant eyeballs on Denmark’s coast for 46 days, and the reason is fascinating

The fishermen of the Western Baltic have long faced a feathered dilemma. Great cormorants and gulls are not just looking at the sea; they are expert thieves. Birds have transformed traditional pound nets, big stationary traps used to catch migrating fish, into personal buffets. This is a win for the birds, but a nightmare for the local fishing industry. The situation is dangerous for the animals, who often become entangled in the mesh or face the wrath of frustrated fishermen, aside from the loss of money.

The struggle to find a balance between protecting a livelihood and conserving wildlife led a team of researchers to try something a little unconventional. They decided to try to trick the birds psychologically. They hoped that by placing floating windmills with giant, staring eyes, they could simulate the approach of a predator. The idea was simple: if the birds thought something was after them, they would stay away from the nets.

High-stakes game of peek-a-boo

The device, formally known as the Looming-Eye Buoy or LEB, is basically a small windmill attached to a buoy. On each wing of the windmill, there are sketches of eyes in different sizes. The wind catches the blades, and they spin fast. This creates a " looming " effect. Above, the differing sizes of the eyes create an impression of a predator closing in fast. The sensory trick is supposed to trigger a natural flight response, sending the birds scurrying for safer waters.

The researchers used these “spooky peepers” in this way, as described in a study titled Looming-Eye Buoys temporarily reduce the number of piscivorous seabirds around fish traps, published in the journal Royal Society Open Science. The first results were nothing less than a triumph for the scientists. The difference was clear just four days after the LEBs were bobbing in the water. The sites with the googly-eyed guardians had almost four times fewer birds than control sites with no devices. For a moment, it seemed that the valuable catch of herring and mackerel had at last been protected by a low-tech, harmless answer.

Previous efforts to solve the problem had often backfired. Some fishers tried to cover the traps with extra netting, but the cormorants proved to be Olympic-level swimmers, diving deeper and getting into the traps from below. Other efforts included constructing small “hiding chambers” in the nets for the fish. This kept the fish safe, but created a new tragedy: birds would get trapped in these smaller spaces and drown. The LEB was supposed to be the humane option that kept everyone- fish, birds, and humans- safe and happy.

When the scare factor wears off

But nature is rarely so easily fooled for long. But as the weeks went by, the spinning eyes began to lose their effect. But on the 46th day of the trial, the researchers saw a frustrating trend. The ‘fear factor’ had gone. The birds, including the clever herring gull and the greater black-backed gull, had worked out that these staring eyes were all bark and no bite.

The study showed that the populations of birds had fully habituated to the device about one month after the implementation of the LEB. The terrible predator they used to be afraid of turned out to be just a harmless, spinning toy. The difference in bird numbers between the "protected" nets and the regular nets was not significant any more. The birds had called the researchers' bluff and returned to their perches on the wooden poles of the pound nets to wait for their next easy meal.

This habituation phenomenon is a huge hurdle in wildlife management. Animals, and especially very smart seabirds, are very good at assessing real risks and false alarms. The Looming-Eye Buoy is a beacon of hope, but also a reminder that the battle between human industry and animal instinct is a constant cat-and-mouse game or in this case, a gull and buoy. For now, the search is on for a way to keep the dinner plate safe without losing the “scare” in the scarecrow.