Added by David Sandercock on December 6, 2010
Poisonous metal compounds polluting our water systems are affecting bird sexuality, say a recent study.
It is reported that even small amounts of methylmercury in the water supply of white ibises, has caused male birds to pair up with each other. As a result, fewer female birds are able to breed and offspring is reduced.
It is the first study to show how a pollutant can change sexual preference, although Peter Frederick, who led the study, explained that he was aware that mercury could reduce the level of male testosterone, “But we didn’t expect this. In the worst-case scenario, the production of young would fall by 50 percent,” he said.
The study analysed 160 white ibises and their response to being fed low levels of methylmercury; one group was fed 0.3 parts per million (ppm), regarded as too high a level for human consumption; one group was fed 0.1ppm; one 0.05ppm, a level the birds are thought to be exposed to frequently; and the last group ate food free of poison.
All three groups that received methylmercury in their diet reported significantly more homosexual males. The effect increased with the level fed; the 0.3ppm group reported 55 per cent of males displaying this behaviour.
Overall, 81 per cent of nests reported as unproductive was attributed to male-male mating.
Although the researchers expect that a similar effect is possible in other birds, it is unclear what the effect in mammals would be.
Methylmercury is a kind of mercury, also known as quicksilver. It has been known to enter our waterways from various industries for many years.