Seasonal Regulation of Reproduction in Muroid Rodents

Abstract

Synopsis. This paper offers a conceptual scheme dealing with the way environmental factors influence reproduction in muroid rodents. The combination of small size, short life span, and the fact that most environments are relatively unpredictable for short-lived animals, suggests that opportunism must be a key element in the reproductive strategies of most of these animals. Flexibility is assured by the use of dynamically changing multiple reproductive strategies within populations, simultaneous multiple cueing in individuals, modification of an individual's responses to these cues by earlier experiences, and the use or lack of use of predictors of different kinds. Fundamental to understanding the reg? ulation of the size of a mammal's popula? tion is an understanding of the factors that influence its reproduction. As emphasized by Sadleir (1969), however, it is exceedingly difficult to investigate the environ? mental regulation of a mammal's repro? duction in natural habitats. Many facets of the environment can influence a mammal's reproduction, and in the wild most of these factors vary in unison, both momentarily and on a seasonal basis.