Date Published: December 2014
Source: Pan Africa News
Institutions Involved: Duke University; Indiana University
Source: Pan Africa News
Institutions Involved: Duke University; Indiana University
Summary: A study
conducted by David Samson of Duke University and Kevin Hunt of Indiana
University explored the relation between population density of chimpanzees and
their aggression levels in an intraspecific community.
Intraspecific aggression
is hostility amongst individuals of the same species and community. Previous
studies relay the presence of various acts of aggression ranging from
undirected to lethal pinpointed acts of violence among female and male chimpanzees.
Causes of such aggression vary, from male on male competition for higher status
in the hierarchy to claiming dominance over females.
In a recent report, it
was found that population density was a factor that affected intercommunity
aggression among 18 chimpanzees. In this study, intraspecific aggression is
studied: the rates of aggression for the Semiliki chimpanzee community were
recorded and compared to known rates at Gombe and Kanyawara. It was
hypothesized that the Semiliki community would be the most peaceful in
comparison to the Gombe and Kanyawara communities as it has the lowest
population density and largest home range (area of occupancy of the
chimpanzees) among the observed chimpanzee communities.
The Toro-Semiliki
Wildlife Reserve in Western Uganda served as the study area consisting of
approximately a hundred and four chimpanzees of which thirty were male. Data
collection occurred from August 2010 to January 2011 in forty minute periods
during which visible acts of aggression were recorded. Observations that did
not last forty minutes were discarded. Behavior was categorized by the
standards of Goodall. In this study, chases, charging displays and contact
aggression were categorized as aggression.
A total of 34.7 hours of
observation were recorded. Semiliki adult males had a rate of .17 aggressive
acts per observation hour which was half the rate of the Kanyawara sample. A
strong correlation between population density and rates of aggression was
determined as r^2 = .93 for the linear regression model (as the strength of correlation increases as r^2 approaches 1).
In context of this study,
it was determined that male Semiliki chimpanzees experienced less frequent
aggression than male chimpanzees of other communities perhaps due to lower
population density.
The importance of this
study is that it is one of, if not the only, studies to compare large home
range and low population community with a small home range and more population
dense community. The conclusion of the report, as in the previously conducted
study of intercommunity aggression, suggested that “ecology and territory size
are key predictors of violent behavior in general.”
Citation:
Samson D. R. and Hunt K.
D. 2014. Is Chimpanzee Low Population
Density Linked with Low Levels of Aggression? Pan Africa News 21(2):
15-17.
Hi Mahathi,
ReplyDeleteI really like the article you chose. I think that behavior is one of the most interesting phenomenon to study because it is so diverse and so robust. There are numerous variables that regulate behavior, and it seems that population density is one of them. I have heard to territoriality sparking animal aggression, but this is the first time that I am hearing of population density sparking aggression. In regards to the research itself, it is good that these animals were monitored in their natural settings because the natural setting offsets some of the variables. The process of observing the animals must have been an interesting experience. I think that a future study may involve analyzing why population density impacts behavior. It would be interesting to see if the personality of an individual chimpanzee plays a role in its behavior.
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ReplyDeleteHi Mahathi,
ReplyDeleteThis research article that you chose is quite fascinating. There have been tons of studies done on Chimpanzee populations but this is the first time I ever read one regarding population size and their behavior. The results itself show what key role the population density plays not only chimpanzee's, but other species as well. I wonder how quickly the behavior of the populations that showed aggressive behavior would change if they were to be suddenly moved to a larger home range? In other words, I wonder how quickly their behavior would alter. This is definitely an interesting study, and it hopefully will spark more studies like this to rise and teach people more about the behavior of species in the type of communities they live in.