Reproductive Cycles and Environment

Abstract

In all organisms, reproduction is timed through natural selection to occur during those periods of the year that are most propitious for the survival of both parent and young. According to Baker (1938), these favourable conditions are the “ultimate cause” of a particular breeding season; the “proximate causes” which are another set of factors, initiate the sexual cycles at the appropriate time of the year (see Chap. 6). In the following account I will firstly discuss cycles according to the climatic zones, then discuss multi-year cycles and then some special adaptations to unpredictable or extreme environments. The focus of this chapter is on gonadal, mating and nesting cycles, and their timing.