Mammalian reproductive strategies: genes, photoperiod and latitude.

This paper considers how and why natural selection might promote or block the photoperiodic regulation of a mammal's reproduction. The factors most important in making this decision would seem to be the following: life expectancy, length of the female's cycle, feeding strategy, the presence or absence of survival mechanisms like hibernation, and the nature of the seasonal challenges offered by the mammal's habitat. A speculative scheme is offered for the potential utility of this type of regulation dependent upon life expectancy and latitude of residence.