How choosy should you be?

To come to their conclusions, the researchers used a mathematical model to assess how general features ruling the life schedule of the animals, such as how often individuals meet, can mate and die, impact the rate at which individuals mate. Because it takes time to reject a potential mate and find another, the choosier an individual is, the less often it can mate. Thus, although being choosy helps an animal to find partners of higher quality, being choosy also comes with a cost. Although matters can sometimes get complicated -- the evolution of higher choosiness in one sex can either promote or impede selection for choosiness in the other, depending on the conditions -- the researchers find that, if the ecological circumstances are such that individuals spend a large part of their lives searching for mates (e.g., male Mormon crickets, many male spiders), then the cost of choosiness is also high -- and individuals can be expected not to be particularly choosy (it takes too much time). Conversely, when successfully finding a mate takes a small part of the lifespan, choosiness can evolve more readily.

Following this logic, the authors of this study -- published in the scientific journal The American Naturalist -- predict that the species in which everybody is very choosy should be those where both females and males need to wait for a while after mating before being able to mate again -- irrespective of the specific reason for needing to wait. Possible reasons include looking after offspring for a long time or refilling one's semen reserves.