Socioecological Adaptations by Chimpanzees from Animal Behaviour

Researchers Hockings, Anderson, and Matsuzawa, authors of "Socioecological adaptations by chimpanzees, Pan troglodytes verus, inhabiting an anthropogenically impacted habitat" as published in the scholarly journal, Animal Behaviour collected data in Bossou, Guinea over a year long period to examine the living conditions of a group of chimpanzees there. In examining "party size" in both crop raids and wild feeds, they were able to observe the ways in which chimpanzees band together in various ecological environments. This particular study explores the ways in which this particular group of chimpanzees behaves within an agricultural-forest region.

The introduction of the study briefly discussed the realities of human invasion of the forest regions of Guinea and suggests that such intrusions may have a significant affect on chimp resource consumption, activity budgets, party cohesiveness, and other factors directly affecting life for the chimps in the region. One important point of discussion in the beginning portion of the article is the idea that agricultural development by humans directly affects all species of a particular region, both in ways that we can observe directly and others that take more exploration and foresight.

Behavioral flexibility is noted as a process that occurs not just in instances of agricultural development, but also in situations where climate and seasonal changes warrant adaptation from a given species to benefit survival. Climate changes can limit availability of food, but heightened access to human food can change the behaviors particular species exhibit in a given region. The authors cite a study that found that other species of monkeys were found to spend less time foraging for food with an increased access to human food.

Behaviors observed by the researchers were divided into several categories- feeding, moving, resting, and social. Single focal individuals were noted, and the researchers also included mention that the other individuals being observed were not always exhibiting the same behavior as the focal individual.

This article in particular is important in that it gives us an insight into the affect human populations have on the well-being of various animal species. Minor intrusions can make significant changes in the overall lifestyle of an animal. In some respects, small differences were found in instances such as party cohesiveness, but significant differences were found in the area of activity budgets. More studies focusing on similar and different animal behaviors will allow for a more definitive outlook on chimp life.

Source: Socioecological adaptations by chimpanzees, Pan troglodytes verus, inhabiting an anthropogenically impacted habitat from Animal Behaviour by Kimberley J. Hockings, James R. Anderson, and Tetsuro Matsuzawa. USD students may find the article via Copley Library at http://0-www.sciencedirect.com.sally.sandiego.edu/science/article/pii/S0003347212000036.

Territorial Behavior

What is a territory? In order to understand the territorial behaviors of chimpanzees, its important to know what we mean by territory. A territory is an area that is taken up by a community which includes all of its resources like food, mates, or breeding sites.  A home range is an area where chimpanzees can eat, breed, and raise their young. What's the difference you ask?  Not much, the main difference is a territory is defended by the group where a home range is unprotected.Chimpanzees exhibit a behavior known as boundary (territory) patrolling.  The males chimpanzees of a social community will walk around their territory in a straight line.  These chimps walk along the edge of their territory  and the neighboring territory in slience, searching for any predators or other chimpanzees from other communities.  If the group comes across another chimpanzee they will attack it in attempt to kill the chimp.  These attacks do not stop at other male chimpanzees, they have been recorded attacking female chimpanzees and their young and eating the remains.  How can animals that seem so sweet have these episodes of hatred and violence?  Most researchers feel the main reasons behind patrolling are: food availability, hunting activity, presence of estrous females, intruder pressure, and male party size.  Other studies confirm the idea that patrolling takes place in order to increase the size of their territory.  It makes sense that with a larger territory comes more food and larger variety of estrous females.  These patrol groups are usually made up of males, on occasion a female will join the group but they are usually infertile.  The average patrol time is 2- 2.5 hours.  Research on the Ngogo Community shows there is strength in numbers, especially when there is an increase of males within the community.  

We see the positive side of patrolling, females, food, larger territory, dominance over other communities, but to anything positive there is something negative.  What are the negative outcomes of patrolling?

A study by Sylvia J. Amsler attempts to find the costs to patrolling.  She hypothesized that chimpanzees spend more time walking and less time eating when they are on patrol.  She studied the Ngogo community for 14 months and observed 29 patrols.  The amount of work these patrollers are putting in takes a toll on their physical well being.  Needless to say, a patroller should be in tip top physical condition to perform successfully during a patrol.  If a chimp lacks the physical strength then their chances of surviving during a fight with other chimpanzee communities shrinks.  Amsler study shows that patrolling takes a toll on a chimpanzee physically.

Territorial behaviors may seem like a male- dominated characteristic but females are impacted by it as well.  Most females move from one tribe to another around puberty and will stay there through adulthood.  Other females move from one group to another depending on the males territorial behaviors.  The more a female moves from one group to another the less likely her offspring is to survive.  A main predictor of female moving is based on two things: food availability and male territorial behaviors.


References
http://onlinelibrary.wiley.com/doi/10.1002/ajp.20757/abstract
http://chimpanzeeinformation.blogspot.com/2011/01/chimpanzees-do-boundary-patrolling.html
http://www.sciencedaily.com/releases/2005/10/051018072735.htm
http://www.eva.mpg.de/primat/staff/boesch/pdf/jour_prim_ter_char.pdf
http://www.sciencedirect.com/science/article/pii/S0003347201919165

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