Scientists have found that high levels of mercury in the diet of male American white ibises (Eudomicus albus) turns them homosexual.
Researchers from Florida and Sri Lanka were trying to discover why mercury reduced fertility in the birds, but were shocked with the results. Dr Peter Frederick from the University of Florida, said: “We knew mercury could depress their testosterone levels but we didn’t expect this.”
A group of white ibises were fed food pellets containing levels of mercury equal to that measured in the shrimp and crayfish that make up the birds’ wetland diet. What was discovered was that the higher the dose, the more likely the bird was to pair up with another male, particularly as males with higher doses of mercury performed far fewer courtship displays, so they were more likely to be ignored by females.
With levels of mercury rapidly rising in aquatic environments the scientists say this could have significant consequences for all marine and wetland animal fertility. Although they don’t know exactly how the mercury does have this effect, they believe it disrupts hormonal signalling.
Dr Frederick said: “We’re seeing very large reproductive effects at very low concentrations. So we really need to be paying more attention to this.”
Gary Heinz, a wildlife researcher for the US Geological Survey in Maryland, said: “Mercury cannot be broken down, only moved about and transformed from one chemical form to another. Mercury is a serious problem in many aquatic environments.”
This story first appeared in our December 8 edition.