Sexual swelling, receptivity, and grouping of wild pygmy chimpanzee females at Wamba, Zaïre
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- Furuichi, T. Primates (1987) 28: 309. doi:10.1007/BF02381014
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The sexual swelling and copulatory behavior of ten pygmy chimpanzee (Pan paniscus) females in a wild group were studied at Wamba, Republic of Zaïre. Since the maximum size of the sexual skin revealed great individual variations depending on age and adolescent females showed little cyclic fluctuation in size, the sexual swelling was measured according to its firmness which periodically fluctuated in all age classes. The duration of maximum swelling and the cycle length were longer inP. paniscus than inP. troglodytes. Although pregnant females and those with newborn infants were sexually inactive, females with infants older than 3 years copulated as frequently as those without dependent infants. Contrary to previous reports on the sexuality ofP. paniscus, copulation was mostly restricted to the maximum swelling phase. All females were usually found in a large mixed party containing both sexes and offspring, regardless of their sexual receptivity.