Optimal duration of male-female exposure to optimize conception in the grasscutter (Thryonomys swinderianus)

Abstract

The optimal duration of male-female exposure needed to achieve pregnancy in grasscutters was investigated. Sexually mature male and female grasscutters were paired until mating had occurred. The outcome of the pairing namely: the female’s acceptance to mate (sexual receptivity), conceive and deliver were investigated by separating the female from the male immediately after mating and subsequently monitoring the female until parturition. The females accepted mating after spending between 18 to 192 hours with the male. The first three days of a two-week male-female exposure resulted in 80% (n = 30) sexual receptivity, 76.3% (n = 29) conception and 71.4% (n = 28) parturition compared to the remaining eleven days, which resulted in 16.7% (n = 30) receptivity, 17.2% (n = 29) conception and 17.9% (n = 28) parturition. The difference in duration of exposure for the first three days of pairing and the rest of the exposure period (eleven days) was significant. Duration of pairing and pairing outcome for the two periods were cross-tabulated and noted to be negatively associated for sexual receptivity, conception and parturition, suggesting that the optimal duration of pairing grasscutters to achieve pregnancy is three days. It is concluded that the common practice of permanently pairing the male and female to achieve pregnancy, which sometimes results in cannibalism of the neonates by the male, is avoidable and the overly long duration of exposure is not necessary.