Detection of mating, pregnancy and imminent parturition in the grasscutter (Thryonomys swinderianus)

Abstract

This study was undertaken to establish methods for detecting mating, pregnancy and imminent parturition in the grasscutter to aid in the captive breeding of the species. Nineteen female grasscutters were hand-mated and subsequently individually caged to determine the outcome of male-female contact (i.e. mating, conception and parturition) and the cardinal signs that accompany them. The signs of mating were detected by monitoring changes in the perineum of the female before and after mating; the signs of pregnancy by monitoring changes in the perineum of the female, changes in weight gained post-mating and presence of foetuses in utero by abdominal palpation; while the signs of imminent parturition were detected by monitoring expectant mothers with distended abdomens for change in feeding/drinking habits, behaviour and posture. The findings of the study suggest that mating in grasscutters is always manifested by vulval congestion, which is sometimes accompanied by vulval oedema and protrusion of the vaginal wall. Pregnancy is manifested by a definite change in body weight four weeks after mating and by intermittent vaginal bleeding and palpation of foetuses in utero five weeks after mating. Parturition is imminent within three days when the expectant mother stands on only its hind legs, and it is a day away when the change in posture is combined with frequent looks at the lower abdomen. The grasscutters give birth to precocious young after 148-158days of gestation. Mating, pregnancy and imminent parturition are therefore detectable in the grasscutter by visible cardinal signs.