Ecological Adaptation and Mammalian Reproduction

摘要: Some of the major variations in mammalian reproductive cycles are discussed from viewpoint their broad adaptive values. In natural populations a nonpregnant cycle is an exception long-lived animals and disaster short-lived prey species. Acceptable alternatives either to safeguard agaisnt occurrence or recover recycle as quickly possible. Mammalian female categorized Type I II III. both ovulation pseudopregnancy spontaneous. Subtype A includes medium length B long cycles. induced spontaneous with similar subtypes. III corpus luteum formation but via release luteotropin following copulation. Induced delayed implantation seasonal breeding postpartum estrus serve different functions population. It appears that more widespread phenomenon occurs restricted number Delayed implanatation widely scattered species groups within many orders also physiological controls vary. At least some degree seasonality activity almost universal natural.a Postpartum seems have developed independently times its distribution sporadic throughout speices. The necessity trying understand significance seen stressed. After basic patterns established appropriate can be selected test hypothesis rather than haphazardly studying forms just because they available.