Seasonal Variation in Gonadal Steroids of Males and Females in the Cape Mole-Rat (Georychus capensis): The Potential for Opportunistic Breeding

Abstract

Urinary testosterone concentrations in males and urinary progesterone and oestradiol concentrations in females were measured in the Cape mole-rat (Georychus capensis) and compared for the summer and winter periods. The Cape mole-rat breeds seasonally, with sexual activity and subsequent pregnancy recorded during the winter months in the southern hemisphere. Despite the fact that it has a distinct breeding season, seasonal differences in urinary hormone concentrations of both male and female Cape mole-rats were not statistically significant. This finding supports the notion the Cape mole-rat may have the opportunity to operate as an opportunistic breeder if fortuitous environmental conditions arise, such as unseasonal rainfall, occurring at these normally non-favourable times of the year.

Pre- and postcopulatory competition affect testes mass and organization differently in two monophyletic mole-rat species, Georychus capensis and Fukomys damarensis

“…Cape mole-rats (CMR), Georychus capensis, are solitary, territorial, and aggressive toward conspecifics outside the breeding season (Bennett and Jarvis 1988a). Territoriality and aggression stop during a short breeding season in May-June (Bennett and Jarvis 1988a;Oosthuizen and Bennett 2009) when males signal to females by drumming with their hind feet (Bennett and Jarvis 1988a)-both males and females may mate with multiple partners (Oosthuizen and Bennett 2009)…”

“…Cape mole-rats (CMR), Georychus capensis , are solitary, territorial, and aggressive toward conspecifics outside the breeding season ( Bennett and Jarvis 1988a ). Territoriality and aggression stop during a short breeding season in May–June ( Bennett and Jarvis 1988a ; Oosthuizen and Bennett 2009 ) when males signal to females by drumming with their hind feet ( Bennett and Jarvis 1988a )–both males and females may mate with multiple partners ( Oosthuizen and Bennett 2009 )–and females are induced ovulators ( van Sandwyck and Bennett 2005 ). There is therefore a high rate of female multiple mating, with female-biased operational sex ratios in populations across different geographic areas ( Visser et al 2017 ), reducing male competition for females and precopulatory aggression.…”

The pattern of reproduction in the mole-ratHeliophobiusfrom Tanzania: do not refrain during the long rains!

“…All solitary South African species of bathyergid mole-rats studied to date have been reported to be seasonal breeders with their reproduction linked to rainfall Herbst et al 2004;Hart et al 2006). In contrast, the majority of social mole-rats breed throughout the year 2011;Oosthuizen and Bennett 2008). There are, however, two social species which breed seasonally with rainfall; the common mole-rat, Cryptomys hottentotus hottentotus (Lesson, 1812) which occurs sympatrically with the solitary mole-rats Georychus and Bathyergus mole-rat genera (Spinks et al, 1997;1999), and the highveld mole-rat, Cryptomys hottentotus pretoriae (Roberts, 1913)(van Rensburg et al 2002, van der Walt et al 2001.…”