title: Characterization of the oestrous cycle and mating season of squirrel monkeys from copulatory behaviour.
abstract: Observations of the behaviour of squirrel monkeys, including 8 opposite-sex pairs during daily 30-min social encounters and 2 mixed-sex permanent groups during daily 30-min observation sessions, over a 14-month period were used to determine the periodicity of the oestrous cycle and annual mating season. The median and modal length of the oestrous cycle was 8 days, within which copulations were limited to a 1--2 day period. In a cyclic female, plasma progesterone levels over a 24-day period dropped from 85--151 ng/ml to 25 ng/ml 2 days before oestrus. In non-cyclic females plasma progesterone values were less than 15-4 ng/ml. Males exhibited a 6-8--19-7 week 'season' of copulation and ejaculation. The onset of this 'mating season' in August coincided with the annual peak in male body weight (the 'fatted male' phenomenon).
mesh_terms: D000818:Animals; D003307:Copulation; D004971:Estrus; D005260:Female; D000882:Haplorhini / Q000502:physiology*; D008297:Male; D011247:Pregnancy; D011374:Progesterone / Q000097:blood; D012453:Saimiri / Q000097:blood / Q000502:physiology*; D012621:Seasons; D012726:Sexual Behavior, Animal / Q000502:physiology*
chemical_list: D011374:Progesterone