For 25 years, a mysterious killer has been released in 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 at or near Lake DeGray, Arkansas. At first, the birds seemed untouched. But during an autopsy, scientists discovered lesions in the brain and spinal cord, a condition they called avian vacuolar myelinopathy (AVM). Researchers at the Department of Fish and Wildlife searched for diseases or toxins such as DDT that could cause this debilitating disease, but found nothing.
The mystery remained unsolved.
The killer reappeared a few years later in Carolinas, Georgia and Texas. In addition to bald eagles, he had begun attacking waterfowl, such as Canadian geese, flakes, and Mallard ducks. First he made the birds unable to fly. They stumbled around, their wings fell, they looked catatonic or paralyzed. Then – in just five days – they died.
Now in a paper published today in Science, An international team of researchers from Germany, the Czech Republic and the United States has finally identified the culprit, a previously unknown neurotoxin called aetochtonotoxin, which could be caused 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 Georgia-South Carolina border. “I have seen the death of the eagle in previous events, but this was the reservoir in which I had done my dissertation research,” she says. “It was an interesting mystery, but a kind of success at home. This was the tank I was working on and I saw a lot of eagles flying over. ”
When Wilde collected dissertation data in the mid-1990s, there was not much vegetation growing in the tank. But when he returned a few years later, the lake was 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 hydrilla was originally launched in the US in the 1950s when it overtook an aquarium and someone threw it into a waterway in Florida. Since then, it has become one of the most dangerous aquatic weeds in the country, thriving in freshwater lakes from Washington to Wisconsin to the Carolinas.) Wilde began to wonder if the death of the eagle and the presence of this new plant were linked.
But Wilde had to interrogate all potential suspects. It began by sampling the water and sediments of the lake for bacteria. He came empty-handed. But when he began examining the leaves of the hydril plant, he found colonies of previously unknown cyanobacteria. She called her Aetokthonos hydrillicola, “The Eagle Killer Growing on the Hydra.”
