Vaginal Fatty Acids Produced by Chimpanzees during Menstrual Cycles
Akiko Matsumoto-Oda, Ryo Oda, Yukako Hayashi, Hiroshi Murakami, Norihiko Maeda, Kiyonori Kumazaki, Keiko Shimizu, Tetsuro Matsuzawa
It is suggested that an olfactory signal is a proximate factor in menstrual synchronisation and ovulation suppression, as well as being a sexual attractant [Jolly, 1967; Michael and Keverne, 1968, 1970; Wallis, 1985]. Adult female chimpanzees (Pan troglodytes) are in maximal swelling for 10ñ13 days of their 32- to 36-day sexual cycle, and ovulation occurs during the last 1 or 2 days of the maximal swelling period [Graham, 1981]. Although observers are unable to determine from physical appearance when ovulation starts, male chimpanzees are reported to change their behaviour between quiescent swelling and maximal swelling or early tumescence and periovulatory periods [Tutin, 1979; Hasegawa and HiraiwaHasegawa, 1983; Takasaki, 1985; Matsumoto-Oda, 1999]. If males can determine the timing of ovulation, one cue may be an olfactory signal. Fox  identified six fatty acids from the vagina of chimpanzees. No significant change in levels, however, has been seen between the cycling and noncycling periods. Females have a fixed rhythm of sex hormone production that is said to influence the grade of substance secretion and olfaction [Wallis, 1992]. Swelling of sexual skin is related to secretion of oestrogen in the follicle period, and diminution is related to a decrease of oestrogen and increase of progesterone [Graham, 1981]. Vaginal mucus and low-grade fatty acids responding to the swelling in captive chimpanzees were quantified during this study.
Olfactory signal, Sexual attractant, Fatty acids, Periovulatory period, Pheromone, Chimpanzees