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