Photo: mauricholas/ Maureen Leong-Kee, Flickr, CC BY
Pollution has long been known to bear various impacts on animals' reproductive behavior. But rarely is the effect so pronounced as what scientists have observed happening to bird populations that ingest the poisonous metal compound methylmercury. Researchers have found that when even low levels of the compound enter their diets, male birds choose to attempt to mate with other males, and snub females.
This poses a threat to bird populations, as fewer mating groups lead to fewer birds in future generations. It was already known that male birds that ingested mercury showed lowered levels of testosterone and showed less of a proclivity to mate. But this is the first time that there's evidence that mercury could alter an animal's sexual preference.
The UK's Daily Mail has more on the experiment:
U.S. researcher Peter Frederick captured 160 young white ibises - a coastal wading bird - and gave them food laced with methylmercury. The birds were split into four groups. One group ate food with 0.3 parts per million (ppm) methylmercury, which most U.S. states would regard as too high for human consumption. A second group was fed 0.1 ppm, and the third 0.05 ppm, a low dose that wild birds would be exposed to frequently. The fourth group received food clear of the poison.
All three dosed groups had significantly more homosexual males than the control group. Male-male pairs courted, built nests together and paired off for several weeks. Higher doses increased the effect, with 55 per cent of males in the 0.3 ppm group affected. Overall, male-male mating was blamed for 81 per cent of unproductive nests in the dosed groups.
Needless to say, it's rather alarming that even trace amounts of methylmercury -- which is notorious for turning up in groundwater near industrial operations -- can have such a substantial impact on wildlife.