Mate choice rules in animals

We identify several fundamental properties of how females choose mates and propose statistical methods to test hypotheses about them. Virtually, all studies of mate choice have implicitly assumed that choice involves what we call strict preference. By that we mean that all the properties of a stimulus can be reduced to a single preference value that is independent of other stimuli, and that the stronger a female's preference for a male, the more likely she is to choose him. An important consequence of strict preference is that it guarantees that females cannot show intransitive choice (where male X1 is preferred over male X2, and X2 over X3, but X3 is preferred over X1). We find general conditions for the strict preference paradigm to apply in the simple situation where females choose between two potential mates. We illustrate how these conditions can be tested statistically using data on mate choice in túngara frogs, Physalaemus pustulosus. The results were not consistent with any of the standard models for strict preference. On the other hand, we also failed to find statistical support for intransitive choice. We suggest that understanding mate choice will require deeper analysis of the most basic properties of the choice rules.