An increase in annual loon deaths from a strain of botulism is sounding alarms among wildlife officials in Michigan.
It's been common over the years for common loon deaths to hit the hundreds but the numbers reached several thousand in 2010 and 2012, according to The Detroit News.
Invasive species such as mussels and gobies, and algae called Cladophora may be factors in the increased deaths, experts say.
"Before these outside factors were introduced, the number of loon deaths from botulism wasn't as bad as it is now," JoAnne C. Williams, state coordinator for Michigan Loon Watch, a volunteer organization, told the newspaper. "But they are increasing the instances and the severity of the die-offs."
Botulism thrives in the Great Lakes sediments that have low oxygen. That sediment is picked up by bottom-feeding invasive species. When larger fish and birds eat the infected fish and mussels, the botulism moves up the food chain to the loons. Officials estimated the number of loon deaths in Michigan reached a high of 7,500 in 2007. The deaths were less than 200 each of the next two years, but climbed to 2,677 in 2010 and 3,947 in 2012.
Other migratory birds have been affected by die-offs but the deaths of loons tend to gain the most attention.
"I would say it has to do with the call of the loon," said Wendy Tater of the Michigan Audubon Society. "It's really kind of ... a lot of people describe it as haunting. It travels over several miles.
"There's something about being out in the wilderness and hearing it that's just very special."
Determining where loons are exposed to botulism is difficult because of the vastness of the Great Lakes, said David Blehert of the U.S. Geological Survey's National Wildlife Health Center in Wisconsin. But scientists need to do that to help figure out a solution.
"If we can identify the places and the situations where (where botulism is transmitted), then it may be possible for us to go in and manipulate the conditions there," Blehert said.
Information from: The Detroit News