Changes in forest fragment sizes and primate population trends along the River Tana floodplain, Kenya

The Tana River forest patches significantly decreased in total area by 1875 ha (34.5%), from 5439 to 3564 ha between 1979 and 2000. The area covered by forests outside the Tana River Primate National Reserve declined by 1246 ha (38%) from 3283 to 2037 ha. This loss was higher than that inside the reserve, where total forest area reduced by 629 ha (29%) from 2156 to 1527 ha. The numbers of Tana River red colobus (Procolobus rufomitratus) and Tana crested mangabey (Cercocebus galeritus galeritus) groups were significantly correlated with forest sizes suggesting that both red colobus and crested mangabeys are likely to be affected by forest loss and fragmentation. However, comparison of the 1974/75 and 2001 census data did not reveal any significant change in the number of groups of either the red colobus or crested mangabey. The two endangered primates may have developed strategies to cope with a shrinking habitat. © 2005 African Journal of Ecology.