For 25 years, a mysterious killer has been freed throughout South America, responsible for the deaths of more than 100 eagles and thousands of other birds. The first victims were found in the fall of 1994 and the winter of 1995, when 29 bald eagles died in or near Lake DeGray, Arkansas. At first, the birds looked intact. But during an autopsy, the scientists found injuries to the brain and spinal cord, a condition they called avian vacuolar myelinopathy (AVM). Researchers from the Department of Fish and Wildlife looked for diseases or toxins like DDT that could cause this debilitating disease, but found nothing.
The mystery was not solved.
The killer reappeared a few years later in the Carolinas, Georgia and Texas. In addition to bald eagles, it had begun attacking waterfowl such as Canada geese, coots and mallards. First he made the birds unable to fly. They stumbled on their drooping wings, looking catatonic or paralyzed. Then, in just five days, they were dead.
Now, in an article published today in Science, an international team of researchers from Germany, the Czech Republic and the United States have finally identified the culprit, a previously unknown neurotoxin called aetoctonotoxin, which could be produced by a deadly combination of invasive plants, opportunistic bacteria and chemical pollution in lakes and reservoirs.
To find this new toxin, the scientists had to work together as detectives, assessing the crime scene and questioning the suspects. Susan Wilde, a professor of aquatic sciences at the University of Georgia, began investigating the mystery in 2001 when 17 bald eagles died in Lake J. Strom Thurmond, an artificial reservoir on the border between Georgia and South Carolina. “I had seen the death of the eagle before in past events, but this was the reservoir where I had done my dissertation research,” he says. “It was an interesting mystery, but it was a success. That was the reservoir where I had worked and I saw many eagles flying overhead.
When Wilde had been collecting data for his dissertation in the mid-1990s, there was not much vegetation growing in the swamp. But when he returned a few years later, the lake had been overtaken by an invasive plant called hydrilla, which is easy to grow and had become a popular plant for fish tanks. (It is rumored that the hydrilla was initially launched in the United States in the 1950s when it overtook an aquarium and someone threw it into a Florida waterway. It has since become one of the aquatic weeds. most pernicious in the country, which thrived in freshwater lakes From Washington to Wisconsin, Carolinas.) Wilde began to wonder if the death of the eagle and the presence of this new plant were related.
But Wilde had to question all possible suspects. He began by taking samples of the water and sediment from the lake to find bacteria. He came out empty-handed. But when he began examining the leaves of the hydrangea plant, he found colonies of an unknown cyanobacterium. She named him Aetokthonos hydrillicola, “The Killer of the Eagle Growing in the Hydra.”
