Captive breeding is the last hope for some animal species that have been all but exterminated in the wild. This is often complicated and frequently unsuccessful, however. In monomorphic species (where the sex of the individual bird cannot be established from external distinguishing marks), which includes many eagles, breeding efforts often founder on the difficulty of identifying potential breeding pairs.
Billy Lee Lasley, after earning a doctorate in physiology from the University of California at Davis, was working as a research endocrinologist at the San Diego Zoo when he received a 1976/78 Rolex Award for his project to develop a non-invasive method to identify the sex of these types of birds.
Lasley’s preliminary laboratory studies indicated that faecal steroid analysis — the examination of bird droppings — offered a promising approach to assessing gonadal function in most, if not all, bird species, and hence to verifying their sex. The method also offered the advantage of being simple, economical, and stress-free for the birds. However, the technique needed validation through laboratory work on a large number of species.
Twenty Years’ Work
The only valid way to check on reliability was to correlate the hormonal findings with an autopsy at the time of the bird’s death. Such a complicated procedure was unrealistic at a single site. Lasley therefore proposed setting up an international centre at the San Diego Zoo Research Department where the gonads and faecal samples of endangered birds that had died would be sent for evaluation.
Lasley’s plans to develop an international evaluation centre in his own country have progressed slowly. "Progress has not been as good as I would have liked," he observes, "simply because this type of research does not attract the same amount of money as research on humans or commercially valuable animals."
Furthermore, applying the sex identification procedure to the hundreds of species that exist would take a lifetime. And the biggest obstacle has been the severe restrictions on biological samples imported into the United States. Therefore, Lasley explains, in order to achieve the goal of an international exchange of information, "we have concentrated on exporting this technology to research centres in countries such as Costa Rica."
At the same time, competing methods of identifying the sex of monomorphic birds have been developed, although they are stressful for the birds. One method involves inserting a tube into their abdominal cavity to visualise the gonads, and the other requires a blood sample which has the added disadvantage that it has not yet been developed for all species.
Lasley remains convinced that his method is better because of its reliability and non-invasive nature. "The method has shown to be successful in every species attempted to date with the single caveat that the birds must be examined in their breeding season. The application of faecal steroid evaluations has reached virtually every zoo in all developed countries and is now being used by field biologists for assessing reproduction in free-ranging animals."
Application to Humans
Interestingly, the most significant application of Lasley’s work may apply to humans rather than birds. Most recently, Lasley has adapted his method to analyse the concentration of hormones in women’s urine and thus monitor the reproductive health of patients who may have been exposed to environmental chemicals. This is a growing area of concern, particularly in industrialised countries, where experts believe many cases of infertility or birth defects may be attributed to environmental causes.
Lasley has moved on from the San Diego Zoo to become a full professor at the Schools of Veterinary Medicine and Medicine at the University of California at Davis. His work there continues to focus on research into human and animal reproduction, but he is also closely involved in training young researchers preparing for their doctorates.
"Winning the Rolex Award brought recognition to me and my field of interest," says Lasley. "I have no doubt that my research career would not have progressed as well without it." The 50,000 Swiss francs from the Award was entirely invested in science since Lasley donated it to the San Diego Zoo for its research programme. However, he confides, "the most important part was the gold chronometer. It is a constant reminder to me and everyone I meet that I did something that others thought was of value."
Published in 1996