reproduction

Chimpanzees live in social communities.  Their reproductive rituals demonstrate this fact.  Males are capable of reproducing by 16 years of age.  Females reach estrus at 10 years old.  Estrus is characterized by anogential swelling which is swelling of the anus/genital area.  This swelling lets the males know they are old enough to reproduce.  Traditionally, female chimpanzees will leave their “home” communities for another social community.  During this period of transition, females are infertile although they still show the signs of maturity, swelling.  During this transition period, females will participate in sexual relations with males even though they are incapable of becoming pregnant.  This is thought to be a form of protection for the females and their young.  If a female chimpanzee enters her new social community  and gives birth without her offspring being from a member of that community then she has a chance of being rejected by the community and having her young killed by the males of the group.  This is called infanticide.  Infanticide is thought to attribute to sexual selection theory.  Infanticide induces a female’s cycle allowing her to reproduce before the 3-5 year interbirth interval period.  Once her cycle begins and is ready to mate, then the males of the new community will know the offspring is in fact a part of their community and will refrain from killing it.  Research has shown that not only males partake in infanticide.  Females have also been shown to kill the offspring of other females for reasons researchers are not definite about.  The two possible reasons for this are isolated cases of pathological behavior and/or dominance rank in females.

When is a good time? Anytime!

There has been no record of a birth season for chimpanzees but there is evidence to show that the number of estrus females in a community does change.  The number of estrous females in a community is positively related with food abundance.  The logic behind this observation is that when females become pregnant they will need more food than when they are not so they go where the food is.

Monogamy?No, thank you!

Most of the time, chimpanzee mating is very promiscuous, as stated earlier, they do live in social communities so why wouldn’t they be overly social? Although females have multiple mates throughout their estrus, they reach the max amount during the 10- day period of tumescence (swelling period).  Research has shown 3 main types of mating patterns exhibited by chimpanzees

1.      Opportunistic, non-competitive mating: characterized by a female who can mate with any male in the group

2.      Possessiveness: occurs when a males develops a short bond with a female and prevents lower- ranked males from mating with her

3.      Consortships: when a male and female leave the group to live on their own, avoiding other chimpanzees.

Mating preferences? Not so much...

Human males are typically more attracted to younger human females because of her ability to reproduce.  This is not the case in the life of a chimpanzee male.  Research has shown, males prefer females who are older than they are.  Human reproduction is restricted by female menopause which comes with age.  Chimpanzees lack this characteristic so males are not attracted to females for that reason.

References

http://obit-mag.com/articles/scientists-publish-first-chimpanzee-mourning-videos

http://www.scholastic.com/browse/article.jsp?id=3756740

http://pin.primate.wisc.edu/factsheets/entry/chimpanzee/behav

http://www.ncbi.nlm.nih.gov/pubmed/6934311

http://www.sciencedaily.com/releases/2006/11/061120130545.htm