Brian Garrett/ FlickrMercury has been implicated in the homosexual behavior of polluted white ibises.
Researchers have found that a pollutant from coal-fired power plants may cause a species of bird to exhibit homosexual behavior, reducing successful mating and nesting behavior.
Mercury seems to cause male ibises to nest together, according to scientists at the University of Florida in Gainesville.
But they caution that what happens in birds doesn't necessarily happen in people.
Indeed, the lead author of the study, Peter Frederick, worries that "people will read this and immediately jump to the conclusion that humans eating mercury are going to be gay," he told the journal Nature. "I want to be very explicit that this study has nothing to say about that."
Mercury is a product of coal-fired power plants. It is also introduced into the environment via the burning of medical and municipal waste.
Mercury is converted into methylmercury, the most toxic and easily absorbed form of the metal found in the environment and is prevalent in wetlands and marine food chains across the globe.
To test whether mercury has an effect on white ibis reproductive behavior, Frederick and his colleagues gathered 160 nestlings in south Florida and split them into four groups. Each group had 20 males and 20 females.
When the birds reached 90 days of age, the researchers began adding methylmercury (the product of mercury in the environment) to their food. One group of birds was given a small amount of mercury, another a medium amount and the third group a lot. The last group, the control, was given no mercury.
Then, for three years, the researchers measured mercury levels in the blood and feathers of the birds and monitored their behavior.
And here's what they found: Not only did mercury accumulate in the birds over time but their behavior and reproductive ability was altered.
Indeed, roughly 13 to 15 percent of the ibis nests failed. And a lot failed because they were being "manned" by two males.
All of the groups, except the control, showed less courtship behavior. As the mercury levels increased, so did the degree, frequency and persistence of homosexual pairings. They also produced fewer eggs than the birds that weren't exposed.
The levels of mercury in all three groups are typical of those found in the birds' natural environment, which suggests that this may actually be occurring in the wild, Fredericks told Nature.
Males that coupled with other males were also less likely to switch partners after their nests failed – a common behavior of ibises whose nests have failed.
The researchers say the next step is to observe animals in the wild, and see whether or not mercury is having an effect there, too.
The study was published Wednesday in the Proceedings of the Royal Society B.
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