Diversity and adaptation in rodent copulatory behavior.

Copulatory patterns of muroid rodents provide an ideal locus for comparative behavioral research. Such patterns are highly stereotyped within and between the individuals of a given species, variable across species, readily elicited in the laboratory, and of great biological significance. Detailed behavioral comparisons of a broad range of muroid species have revealed extensive behavioral diversity that was not anticipated from research confined to laboratory rats. Various muroid species display postejaculatory compulations without sperm transfer, locking, thrusting, and other behavioral patterns. This behavioral diversity appears not to be the result of a simple linear pattern of evolutionary history. Rather, patterns appear to have evolved repeatedly in response to particular selective pressures acting on particular species. While understanding of the adaptive significance of these behavioral patterns remains rudimentary, important beginnings have been made.