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T. E. ROWELL

Summary.

Some of the behaviour of rhesus monkeys, including mating, associating with males, and fighting, is related to seasonal variation, long-term reproductive cycles, and to the menstrual cycle of the females. There was a recognizable breeding season in the colony studied. No behavioural modifications were associated with ovulation, and maximum mating frequency occurred at an infertile stage of the cycle. There were striking behavioural changes associated with menstruation. It is suggested that the term oestrus is not very useful when applied to this species or others with comparable patterns of behaviour.

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T. E. ROWELL

Summary.

Reproductive cycles of female vervets and Sykes' monkeys living in caged breeding groups were followed over 2 years, using a vaginal lavage technique. Both species showed menstrual cycles, and both showed leucocyte peaks in mid-cycle which were assumed to be associated with ovulation. Vaginal cornification patterns were dissimilar in the two species. Sykes' monkeys showed some limitation of copulation to an oestrous period but this was not at a constant stage in the cycle. Vervets appeared to be in continuous oestrus. The gestation period of vervets was confirmed at 165 days and that of Sykes' at about 140 days, which was correlated with a slower rate of development in the infant Sykes'. The caged Sykes' showed two breeding seasons annually, conceptions occurring in the dry seasons but free-living animals are reported as having one breeding season a year. Vervets had a single, long birth season as in the wild but not at the same time as nearby wild groups and not apparently associated with wet or dry seasons.

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T. E. ROWELL and A. F. DIXSON

Summary.

Two adjacent troops of talapoin monkeys were studied near Mbalmayo, Cameroon, during a predicted 3-month breeding season. Mating continued for just over 2 months. One troop began to mate at least 2 weeks before the other, suggesting that, though climatic changes were probably important, precise timing was mediated through some intra-troop social facilitation effect.

Before the breeding season, adult males and females lived in separate sub-groups. Males began to move into female sub-groups before there was any sign of the perineal swellings characteristic of receptive talapoin females. Copulation occurred only with females with medium or large swellings, except towards the end of the season. It is probable that the majority of females were monoestrous. At the height of the mating period, females joined mainly male sub-groups, leaving their infants with the mainly female groups which also included a few males. Copulations were observed in both these types of sub-groups. Consort behaviour was not observed, males frequently returning to all-male sub-groups immediately after ejaculation. Intersexual grooming was not characteristic of sexual interactions. At the end of the season, adults were seen more frequently in groups of their own sex or with juveniles only, and there was some indication that increased aggressiveness by newly pregnant females might be partly responsible for this separation.