The black-and-white colobus monkeys (Colobus angolensis palliatus) of Diani forest, Kenya : behavioural responses to habitat fragmentation

Abstract: The loss of habitat is one of the greatest threats to global biodiversity today. Consequences to a species inhabiting fragmented habitats include: group size changes, altered diets and altered foraging behaviours. In my study I observed Colobus anlgolensis palliatus troops living in the forests of Diani, a highly developed area on the Kenyan coast. I looked for differences in behaviours between three troops inhabiting pristine forest patches and three troops inhabiting highly degraded forest areas. I used focal animal sampling with instantaneous sample points. Morning and evening observations were carried out over two months during the rainy period. The results of my study imply that during the long rains period colobus monkeys in Diani are mainly leaf eaters, fruit or the seeds of these fruit being their next most consumed food item. There were very little differences in sex and age class behaviours except for juveniles. They rested less, groomed themselves less, were more social and moved more than adults. Colobus monkeys foraged more in the evening and rested more in the morning, which may be due to differences in temperature or food digestion time. The troops in the degraded forest areas spent more time in the morning foraging than the troops in the pristine forests, which may be related to diet. The troops in the pristine forests foraged mostly from native plants, and the troops in the degraded forest areas foraged more from exotics than the troops in the pristine forests. The troops in the degraded forest areas also had a higher dietary diversity per observation period than the troops in the pristine forests. Ranging behaviours differed between forest types, possibly reflecting home range quality. The troops in the pristine forests home ranges were slightly bigger than the troops in the degraded forest areas home ranges on average. Home range over lap was a lot higher for the troops in the degraded forest areas, and the troops in the degraded forest areas had to travel further each day. Overall the troops in the pristine forests seemed to be in better shape than the troops in the degraded forest areas. I conclude that if habitat fragmentation continues in Diani, then these highly florivorous monkeys will have a hard time adapting.