Regulation of reproduction in female common mole-rats (Cryptomys hottentotus hottentotus): the effects of breeding season and reproductive status

Abstract

The effects of breeding season and reproductive status on female reproduction were investigated in the common mole-rat, Cryptomys hottentotus hottentotus, a co-operatively breeding rodent that exhibits seasonal breeding and a reproductive division of labour. Body mass, reproductive tract morphometrics, ovarian histology and plasma testosterone concentrations were studied in 80 females from 42 wild-caught colonies. Although the birth of offspring is restricted to the summer, qualitative analysis of ovarian histology revealed that females retained reproductive function during the winter non-breeding period. Seasonal differences were found in ovarian morphometrics and testosterone concentrations and are probably associated with the occurrence of pregnancy in reproductive females during the breeding period. The continuance of reproductive function during the non-breeding period in female common mole-rats parallels the situation in males, and is believed to be important in dispersal in C. h. hottentotus. The non-breeding period coincides with the period of maximal dispersal opportunities in the winter rainfall areas inhabited by the common mole-rat. Reproductive activation in dispersing animals may aid intersexual recognition, assist pair-bond formation and thereby facilitate independent reproduction. Reproductive and non-reproductive females exhibited a similar degree of reproductive function, and as for season, the only clear-cut status-related differences were associated with the occurrence of pregnancy in reproductive females. This absence of a physiologically well-defined suppression of reproduction in female common mole-rats is similar to the situation in males. Incest taboos between philopatric siblings may negate the need for a rigorous suppression of reproduction in subordinate colony members of this obligate outbreeder.