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- Female bonobos, like chimpanzees, have pink genital swellings that appear attractive to males
- In chimpanzees and bonobos these swellings coincide with times of heightened fertility.
- In bonobos, times of maximum genital swellings last about 13.4 days (Paoli et al 2006)
- In chimpanzees, the maximum swelling period is 2 or 3 days less. (Furuichi & Hashimoto 2002)
- Bonobos are sexually receptive for a large portion of their reproductive cycle, even when not near the time for ovulation.
- This trait has sometimes been called concealed ovulation because the male has no clear signal for the optimum time for mating.
- Bonobos also engage in sex in non-swelling phases of their cycle in about 1 out of 3 copulations.
- Chimpanzee females tend to be sexually active only during their maximum swelling phase.
- Visible swelling cycles do not correlate exactly with the menstrual and ovulation cycles, but these visible signs are the ones often documented in field studies as indicators of sexual phase. (Vervaecke et al 1999) (Reichert et al 2002)
- Time between menstrual cycles averaged around 33.8 days for six bonobos studied in managed care.
- Menstrual cycles in most published studies show considerable variation for bonobos.
- Bonobo females may be found with in mixed-sex parties, regardless of the condition of their genital swelling. (Furuichi & Hashimoto 2002, 2003)
- Chimpanzee females may seek to limit their time in groups with males due to the increased difficulty in obtaining food since males are strongly dominant;
- Bonobos may typically have more abundant food resources in their wild habitats and they are also not subordinate to males, so there is little cost to them in being in groups that include males.
- Mutual gazing occurs prior to and during copulation.
- Copulation may occur either face-to-face or with the male behind the female, as in dogs.
- Face-to face copulation occurs in about 1/3 of matings; this behavior is almost unknown in chimpanzees.
- Females may copulate several hundred times for one conception as do chimpanzees. (Hashimoto & Furuichi 2006).
- Females produce first offspring at about 13 or 14 years. (de Waal 1997)
Gestation and Birth
- 231-244 days (about 8 months)
- One animal studied at San Diego Zoo had a gestation period of 255 days. (Kuroda 1989)
- 4-6 years (Kano 1992, de Waal 1997)
Infant: birth to 2 years
- Weight of four newborns studied at San Diego Zoo: 1.27 kg (2.8 lb)
- Bonobo infants grow more slowly than chimpanzee infants, both physically and behaviorally. (Kuroda 1989)
- For the first three months not seen leaving mother.
- At 6 months venture up to 1 m (3.3 feet) away.
- At 10 months may wander up to 4 m (13 ft).
- By one year can navigate on all fours.
- Delayed development may "foster food sharing, behavioral flexibility, complicated communication, matrilineal groupings, female-centric society, and highly tolerant interaction patterns." (Kuroda 1989)
- Adults show high tolerance for young bonobos until they reach puberty around 8 or 9 years.
- Chimpanzees, by contrast, are often threatened by adult males at the time of weaning.
- Infanticide in bonobos has never been recorded. (de Waal 1997)
- Bonobos play "baby" even after weaning by rocking, whimpering, and having temper tantrums.
- More births occur in wild during rainy season.
- Females have been seen nursing two infants of different ages
- Seen in the wild and at sites where food is provided. (Furuichi & Hashimoto 2002) (Kano 1996)
- Only nutrition for offspring during the first year is from nursing; even though it may mouth solid food, it doesn't eat it.
Juvenile: 2 to 5 years
- Juvenile stage for all great apes lasts longer than that of lesser apes and monkeys.
- Play behavior develops by 2 years.
- Around 3 years can locomote nearly as well as adults but still stay within 10 m (33 ft) of their mothers.
- Around 3 years switch to being carried on the back rather than on the mother's chest.
- Weaning around 4 or 5 years.
Adult: individuals that have reached sexual maturity
- Adult body size reached around 14 to 16 years (at Wamba). (Kuroda 1989)
- Sexual maturity for males assumed to be around 9 years.
- Males never leave the group of their mother
- Female sexual maturity similar to males'.
- Females leave their birth groups around 9years.
- Age of first menstrual cycle in six females studied in managed care varied between 6 and 9 years. (Vervaecke et al 1999)
- Age of first pregnancy is usually around 11-13 years.
- Age at female menopause not known, but a 48 year old female at the Frankfort Zoo still had irregular menstrual cycles.. (Jurke et al 2008)
In the wild
In managed care
Furuichi & Hashimoto (2002, 2004)
Hashimoto & Furuichi (2006)
Jurke et al. (2008)
Lee & Guhad (2001)
Reichert et al. (2002)
Vervaecke et al. (1999)
SDZWA Library Links
Fact Sheet Index
Fact sheet index, San Diego Zoo Wildlife Alliance Library
Home page, San Diego Zoo Wildlife Alliance Library
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