Aspects of reproduction and reproductive behaviour inMacaca arctoides

Abstract

Observations are reported from 7 years of breedingM. arctoides in a small caged colony. From a stock of two males and six females 18 offspring have been born and 17 reared despite leaving young with the mother for approximately 2 years and restricted access between sexes. Overt menstrual bleeding is inconspicuous and external signs of oestrus are minimal. Colour change and slight swelling indicate the cycling condition, not the stage of the oestrous cycle. Mean length of cycles was 29.4 days. Copulatory ties have been observed on 15 occasions. Pregnancies lasted 168–183 days. The mean of five exactly timed pregnancies was 178 days. Pregnant animals became lethargic during the last two months of gestation. Nipple enlargement occurred during some pregnancies and females sucked and manipulated their nipples expressing milk. This was also seen in two non-pregnant females caged beside nursing mothers. All 17 successful births occurred at night. Caging mother, latest offspring, and previous offspring together proved successful. Mothers tolerated quite extensive investigation of the newborn by her previous baby, and the interactions that develop subsequently. Older female siblings frequently direct components of maternal behaviour to their younger sibling. Males showed marked interest in young in neighbouring cages, giving the soft “grunt-purr” typically shown to white furred young by adults other than the mother. The age of menarche of females born in the laboratory has steadily decreased through the period of captivity. Sexual behaviour is first seen long before puberty in both sexes, some aspects of its development are described. Two sub-adult males appeared to have failed to develop mature sexual behaviour until it was found that their incompetence was a reversible effect of the presence of an adult male.