The oestrous cycle of the Damaraland mole‐rat revisited: evidence for induced ovulation

• Published in: Journal of zoology (1987) Vol. 314; no. 2; pp. 85 - 95
• Main Authors: Voigt, C., Medger, K., Bennett, N. C.
• Format: Journal Article
• Language: English
• Published: London Blackwell Publishing Ltd 01.06.2021
• Subjects: Bathyergidae; Corpus luteum; Dispersal; Estrus cycle; Females; Fukomys damarensis; Histology; Hormones; Housing; induced ovulation; Males; mole‐rats; oestradiol; Ovaries; Ovulation; Progesterone; Reproduction; Seasonal variations; Seasonality; Social conditions; Social organization; Wire cloth
• ISSN: 0952-8369; 1469-7998
• DOI: 10.1111/jzo.12860

African mole‐rats (family Bathyergidae) show a wide variety of social organization, from strictly solitary to highly social. Within the family, both modes of ovulation, spontaneous and induced, have been found and are thought to relate to seasonality of reproduction and opportunities for dispersal. Damaraland mole‐rats (Fukomys damarensis) are cooperative breeders, which breed year‐round and exhibit high reproductive skew. Reproduction is monopolized by a single female (queen) in each group, and non‐reproductive females in the presence of the queen are anovulatory. The species was previously described as being a spontaneous ovulator; however, subsequent attempts to determine the length of the oestrous cycle have failed. Therefore, we revisited this subject by studying the urinary progesterone and oestradiol profiles over a period of 7 weeks and the ovarian histology of females kept under different social conditions. The first experiment shows that average urinary progesterone concentrations of breeder females paired with a vasectomized male (full physical contact) are significantly higher than those of breeder females kept singly, non‐breeder females kept singly and non‐breeder females kept within their natal group. In the second experiment, we subjected females consecutively to different experimental conditions: full physical contact (stage 1), isolation (stage 2), non‐physical contact (stage 3) and measured their steroid hormone profiles. The females showed elevated concentrations of urinary progesterone during the phase of full physical contact and basal concentrations during the subsequent single housing phase. Correspondingly, no corpora lutea of ovulation were found in the ovaries of these females in the latter phase. During stage 3, in which females were separated from a male by wire mesh (non‐physical contact), one of three females showed elevated progesterone and oestradiol concentrations throughout the sampling period and analysis of ovarian histology revealed a corpus luteum. Together, these results support the view that Damaraland mole‐rats are induced ovulators, in which non‐coital male cues are able to induce ovulation. In order to identify the ovulation mode in Damaraland mole‐rats (Fukomys damarensis), a cooperatively breeding, subterranean rodent with a high reproductive skew, we monitored urinary steroid hormone profiles of females over an extended period of time under different social conditions and analysed their ovarian histology. The females showed elevated concentrations of urinary progesterone when in full physical contact with a male, and basal concentrations during the subsequent single housing phase. Correspondingly, no corpora lutea of ovulation were found in the ovaries of singly housed females. These data provide evidence that Damaraland mole‐rats are induced ovulators.