Pollution ‘makes male birds mate with each other’, say scientists
Water pollution is posing a threat to bird populations by causing males to mate with each other.
Scientists believe poisonous metal compounds entering the food chain can affect sexuality, causing a reduction in offspring.
They found that even relatively low levels of methylmercury in the diet of male white ibises caused the birds to pair up with each other, snubbing females.
Close bond: The white Ibis is one of the birds that is being badly affected by mercury in its diet, new research has shown
As a result fewer females breed and fewer chicks are produced.
Methylmercury is a form of mercury – the metal which is liquid at room temperature and is better known as quicksilver. It has been seeping into groundwater from industry for years.
This is the first scientific study to show how the pollutant appears to alter sexual preference.
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.
‘We knew mercury could depress their testosterone levels,’ explained Dr Frederick.
‘But we didn’t expect this. In the worst-case scenario, the production of young would fall by 50 per cent.’ Other birds would probably be similarly affected, he said.
However, Dr Frederick, of the Florida University, and fellow researcher Nilmini Jayasena, of the Peradeniya University, Sri Lanka, admitted it was far from clear if methylmercury could be linked to similar effects in mammals.
● One of Britain’s most endangered birds has made a comeback.
The stone-curlew reached a low of around 160 breeding pairs in the 1980s, but this year 370 pairs are known to have bred.
Farmers in the South-West and South-East have been working with conservationists to protect nesting areas.
The Nuremberg Code
1) The voluntary consent of the human subject is absolutely essential.
This means that the person involved should have legal capacity to give consent; should be so situated as to be able to exercise free power of choice, without the intervention of any element of force, fraud, deceit, duress, over-reaching, or other ulterior form of constraint or coercion; and should have sufficient knowledge and comprehension of the elements of the subject matter involved, as to enable him to make an understanding and enlightened decision. This latter element requires that, before the acceptance of an affirmative decision by the experimental subject, there should be made known to him the nature, duration, and purpose of the experiment; the method and means by which it is to be conducted; all inconveniences and hazards reasonably to be expected; and the effects upon his health or person, which may possibly come from his participation in the experiment.
The duty and responsibility for ascertaining the quality of the consent rests upon each individual who initiates, directs or engages in the experiment. It is a personal duty and responsibility which may not be delegated to another with impunity.
2) The experiment should be such as to yield fruitful results for the good of society, unprocurable by other methods or means of study, and not random and unnecessary in nature.
3) The experiment should be so designed and based on the results of animal experimentation and a knowledge of the natural history of the disease or other problem under study, that the anticipated results will justify the performance of the experiment.
4) The experiment should be so conducted as to avoid all unnecessary physical and mental suffering and injury.
5) No experiment should be conducted, where there is an apriori reason to believe that death or disabling injury will occur; except, perhaps, in those experiments where the experimental physicians also serve as subjects.
6) The degree of risk to be taken should never exceed that determined by the humanitarian importance of the problem to be solved by the experiment.
7) Proper preparations should be made and adequate facilities provided to protect the experimental subject against even remote possibilities of injury, disability, or death.
8) The experiment should be conducted only by scientifically qualified persons. The highest degree of skill and care should be required through all stages of the experiment of those who conduct or engage in the experiment.
9) During the course of the experiment, the human subject should be at liberty to bring the experiment to an end, if he has reached the physical or mental state, where continuation of the experiment seemed to him to be impossible.
10) During the course of the experiment, the scientist in charge must be prepared to terminate the experiment at any stage, if he has probable cause to believe, in the exercise of the good faith, superior skill and careful judgement required of him, that a continuation of the experiment is likely to result in injury, disability, or death to the experimental subject.
“Trials of War Criminals before the Nuremberg Military Tribunals under Control Council Law No. 10″, Vol. 2, pp. 181-182. Washington, D.C.: U.S. Government Printing Office, 1949.]