Reproductive behavior in Varecia variegata.

Testicle size during the breeding season is related to age and previous social environment of the male. The size of testicles in adult males exceeds that of young males. Adult males' testicles are much larger than the testicles of young males; enlargement starts 2-3 months prior to the breeding season, peaking around copulation day. Subadult males (3-year-olds) are able to develop full-sized testicles and sire offspring, but did so only when housed with adult females and not with their family group. Although females may reach sexual maturity in their second breeding season after birth, they do not necessarily breed successfully. Vaginal estrus lasts considerably longer (2-3 days) than behavioral estrus (6-12 h). Different stages of vaginal estrus can visually be determined by the development of the vaginal region (swelling; appearance of pink point; long, pink slash; opening to round pink circle, and in the latter stage, by smears, confirming the different physiological stages, proestrus, estrus, metestrus). Behavioral estrus appears in the last hours of vaginal estrus. Captive adult females show increasingly hostile behavior to their maturing daughters. These have to be removed from the group when they are sexually mature. The same degree of hostility can be found between fathers and subadult sons during the breeding season. Dominant males show a typical 'guarding behavior' over the entire period of behavioral estrus of the female. They remain close to the female, vigorously preventing other males from approaching or mating with the female. At the beginning and the end of copulations, the female shows a sequence of aggressive behaviors towards the dominant male. Successful copulations can be determined by their duration (1-2 min), and a head-twisting movement of the male during ejaculation. Normally 16-25 copulations occur on copulation day, usually all with the same partners. The average gestation length is 102.5 days. Adult females normally give multiple births, whereas primiparous females tend to have single infants.