Emily Miller
M.A. Conservation Biology, 2010
Mixed-Species Associations of Blue
Monkeys (Cercopithecus mitis) and
Black-and-White Colobus (Colobus guereza)
in the Kakamega Forest, Kenya
My study examined the costs and benefits of mixed-species associations of two primate species: blue monkeys (Cercopithecus mitis) and black-and-white colobus (Colobus guereza),
also known as guerezas, in the Kakamega Forest, Kenya to understand the
nature of the associations between primates with divergent feeding
habits. I observed one group of blue monkeys and three groups of
colobus whose home ranges overlapped with heterospecifics, collecting
data on the frequency and duration of associations, as well as feeding,
aggression and vigilance rates. I rejected the null hypothesis that
associations are the result of chance by using a gas model
(Hutchinson and Waser 2007) that predicts the expected number of associations
that would occur by chance. I found that the association durations,
however, were not longer than predicted by chance except for one
guereza group, which supports a modified null hypothesis that groups
are independently drawn to the same location where they meet. I
examined potential predation avoidance and foraging benefits of
associations. Neither species reduced individual vigilance rates, alarm
call frequencies, nor intense alarm responses in associations, nor did
they increase ingestion rates. Individuals occupied lower forest strata
more often, and had a wider niche breadth in association, suggesting
some foraging benefits, possibly resulting from improved predation
detection when associated. The associations frequently occurred at
forest edges and around human settlements which have exposed
sodium-rich soil (important in both speciesŐ diets), visible insects,
and high-energy cultivated foods (occasionally eaten by blue
monkeys). Both species may be receiving some predation avoidance
benefits of having a larger group at vulnerable edge locations, but it
appears that ultimately they are drawn to these sites, not each other,
because they do not maintain their associations once initiated.
After finishing her MA, Emily completed her PhD at UC Davis studying sturgeon ecology.