Changes in group size and composition of the blue monkeys (Cercopithecus mitis stuhlmanni) between 1984 and 2009 at Ngogo,Kibale National Park,Uganda

Group counts were conducted on five groups of blue monkeys at the Ngogo study site, Kibale National Park, Uganda between January and June 2009. Group sizes were compared with those obtained using similar methods at the same site during 1983‐84 by Tom Butynski. During the present study, group size ranged from 16 to 28 monkeys. The results show that the group size of blue monkeys (Cercopithecus mitis stuhlmanni) has increased significantly between 1984 and 2009. Mean group size has increased over two‐fold from 9 after the fission of group 33 during Butynski s study to 21.6 animals per group in 2009. These results strongly suggest that the density of blue monkeys at Ngogo has increased although census data indicate that group density has remained more or less the same.