Female reproductive cycles and birth data from an Old World Monkey colony

Observations on reproductive cycles and births for a variety of captive Old World monkey species are reported. The majority of the subjects have been group living animals, housed with conspecifics in large outdoor compounds. Reproductive cycles were measured by notation of changes in the degree of female sex skin swellings. Three types of cycles are distinguished: estrus, intrapregnancy, and pubertal. Cycle length periods and the duration of the period of swelling are described for each cycle type. Birth distributions are analyzed for the occurrence of seasonality, and a marked seasonal effect tied to the onset of cycling in pubescent females is noted. The influence of a group formation effect on the timing of the reproductive season in one species is discussed.