of course, the likelihood of conceiving or producing a son or a daughter remains a mystery. The barn swallows nest readily in wooden boxes constructed and placed in a convenient location by the investigator, and large numbers of them can be captured relatively easily in nets. We know, therefore, that male swallows with longer tail streamers tend to have fewer fleas and other external parasites than males with shorter tails, and that females prefer to mate with such males. Other reasonably well-studied natural systems include North American prairie dogs, song sparrows, and a few of the African carnivores, such as lions and hyenas. For none of these do we even approach the degree of understanding we have of what makes lab rats or Drosophila work, particularly in terms of their genetics, but we have some idea about the forces that govern their lives in evolutionary terms, that is, what makes an individual likely to produce more or fewer offspring. Model systems are a good thing, aren’t they? Yes and no. They are a good thing because it would be frustrating in the extreme to have only a rudimentary amount of information about a large number of species, so that we might know a little bit about the mother-infant relationships of seventy-five species of primates but nothing about the adolescence or adulthood of any of them. If we had to reinvent the wheel every time we wanted to study a question about behavior in any species, we would still not have reached the stage where we could, for example, reliably predict the outcome of a dominance interaction between two red deer stags. They are also a good thing because armed with a detailed knowledge of a few species, we can have some hope of coming up with generalizations that will apply, with a few modifications, to many other species—the true definition of a model system. Few people study rats because they are interested in rats per se; they are interested in how to describe general principles of learning, or in the factors governing nerve control of penile erections, or in the inheritance of aggression during early adulthood. This ability to transcend the specific case at hand and make a statement about the way an entire, if small, piece of the universe functions is what science is all about, and it is the strength of the model system. Many of us, of course, are in fact interested in our study animal for its own sake, and spend long hours watching pandas or magpies because pandas and magpies capture our imaginations, appeal to the same sense of belonging that Wing Bamboo had with his loon. It would be difficult to maintain the enthusiasm necessary for the hard work of doing science
sex and the death of a loon
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