The adaptive significance of reproductive delay phenomena in some South African Microchiroptera

In the last 8 years, examples of prolonged sperm storage, delayed implantation and retarded embryonic development have been reported from some South temperate Old World Microchiroptera. It is suggested that in the species concerned, hibernation or prolonged periods of hypothermia restrict all reproductive processes to the summer months (September to April) and that this 8‐month period is too short to accommodate a ‘typical’ microchiropteran reproductive cycle. Consequently some form of reproductive adaptation, in which a period of delay occurs in the reproductive cycle, is one requirement for hibernating bats in subtropical and temperate latitudes. The inclusion of a period of reproductive delay during winter effectively lengthens the reproductive cycle and allows gametogenesis to be initiated in the middle of one summer, and parturition to occur early the following summer. It is suggested that the type of reproductive delay evolved by a species may be related to its pattern of winter activity. SUMMARY It is suggested that in the hibernating members of the Vespertilionidae and Rhinolophidae the typical tropical reproductive strategy of seasonal monoestry has been modified by the inclusion of a period of reproductive delay. The principal effect of this is to lengthen die reproductive cycle so that gametogenesis is initiated in the middle of one summer, and parturition and lactation occur during the following summer, when food is abundant. The diree reproductive delay phenomena recorded in Microchiroptera from Soudi Africa should be regarded as different ways of lengthening the reproductive cycle, possibly determined by the winter activity of the species. Although these ideas are based on observations of the reproduction of African bats, they can equally be used to explain die evolution of reproductive delays in north temperate bats.