Brief communication: Puncture and crushing resistance scores of Tana river mangabey (Cercocebus galeritus) diet items.

Cercocebus mangabeys are characterized by dental traits that have been interpreted as adaptations to eat hard diet items. Although there are data that mangabeys include a large proportion of fruit and especially seeds in their diets, no hardness measurements have been done on mangabeys' food items. This study measured puncture and crushing resistance of food items in the diet of the Tana River mangabey (C. galeritus). Feeding data were collected by the use of scan samples from one mangabey group from August 2000 to July 2001 and from July 2005 to June 2006. Food items were collected during the latter period only, and from the same tree in or under which mangabeys had been observed eating. A portable agricultural fruit tester was used to measure the puncture resistance of fruit and a valve spring tester was used to measure the crushing resistance of seeds. The average puncture resistance of fruit was 1.7 kg/mm(2), and the average crushing resistance of seeds was 12.8 kg. There were no correlations between puncture resistance, crushing resistance, or all resistance scores and frequency contribution to the diet. Resistance scores measured in this study were within the range of hardness scores of fruit and exceeded hardness scores of seeds eaten by other hard object feeders. Although this study supports the interpretation that Cercocebus dental traits are adaptations to hard object feeding, future research should investigate other material properties of food, as well as the role hard diet items play in niche separation and as fallback foods.

Links between habitat degradation, and social group size, ranging, fecundity, and parasite prevalence in the Tana River mangabey (Cercocebus galeritus).

We investigated the effects of anthropogenic habitat degradation on group size, ranging, fecundity, and parasite dynamics in four groups of the Tana River mangabey (Cercocebus galeritus). Two groups occupied a forest disturbed by human activities, while the other two occupied a forest with no human disturbance. We predicted that the groups in the disturbed forest would be smaller, travel longer distances daily, and have larger home ranges due to low food tree abundance. Consequently, these groups would have lower fecundity and higher parasite prevalence and richness (number of parasite species). We measured the abundance of food trees and anthropogenic activity in the forests, the groups' daily travel distances and home range sizes, and censused social groups over 12 months. We also analyzed fecal samples for gastrointestinal parasites from three of the groups. The disturbed forest had a lower abundance of food trees, and groups in this forest traveled longer distances, had larger home range sizes, were smaller, and had lower fecundity. The groups in the disturbed forest had higher, although not statistically significant, parasite prevalence and richness. This study contributes to a better understanding of how anthropogenic habitat change influences fecundity and parasite infections in primates. Our results also emphasize the strong influence of habitat quality in determining daily travel distance and home range size in primates.

Shifting forest composition and primate diets: a 13-year comparison of the Tana River mangabey and its habitat.

We compared the feeding behavior of a group of Tana River mangabeys (Cercocebus galeritus), densities of 25 diet species, and fruit availability of nine species in a 16.25 ha Tana River forest in southeastern Kenya studied in 1988 and in 2000-2001. For both studies, we enumerated all reproductively sized individuals of the 25 diet species and sampled nine of those species monthly for fruit availability. Mangabey feeding data were collected monthly from January to December 1988 and August 2000 to July 2001 using identical methods. We found a 17% increase in stem number of the 25 species between studies. Estimates of fruit production were lower in 2000 for five of the nine species monitored. Species composition of the mangabey diets shifted between 1988 and 2000-2001. We suggest that changes in forest composition may be due to declining human disturbance, elephant loss, changes in the river's hydrologic regime, and the 1997/98 ENSO event. Possible reasons for lower fruit availability are a younger demographic profile of the forest and changes in the river's hydrological regime. Only some of the changes in the mangabey diet mirrored changes in stem abundance and/or fruit availability. Mangabey dietary changes underscore their high degree of flexibility that allows them to persist in such a dynamic forest habitat.

Examination of increased annual range of a Tana mangabey (Cercocebus galeritus) group.

A group of Tana mangabeys (Cercocebus galeritus) has greatly expanded its annual range over three decades: from 17.25 hectares (ha) in 1974 (Homewood [1976] Ph.D. dissertation, University College London) and 18.75 ha in 1988-1989 (Kinnaird [1990a] Ph.D. dissertation, University of Florida) to 46.75 ha in 2000-2001. Utilizing 5-min mapping samples, phenological samples, vegetation data, and statistical and descriptive comparisons with previous data, three hypotheses concerning this range increase were postulated. The hypothesis with the strongest support is an increase in intragroup feeding competition, which was measured by a decrease in fruit availability per hectare and an increase in group size. Fruit biomass estimates of four species individually and of eight species combined showed significant decreases between earlier findings (Kinnaird [1990] Ph.D. dissertation, University of Florida) and this study. Group size decreased from 36 in 1974 to 17 in 1988-1989, and is now 50 individuals. There is no support for the hypotheses that the group is no longer constrained in home range size by neighboring groups or by the extent of forest cover. The changes in group and home range size are also discussed in the context of historical forest loss in the lower Tana River. The ability of the Tana mangabey to increase its home range, especially by traveling through nonforest habitat, is an important aspect of its ecological flexibility in a fragmented and threatened habitat.

Ecological correlates of abundance in the Tana mangabey (Cercocebus galeritus).

I investigated the ecological correlates of abundance in the Tana mangabey (Cercocebus galeritus), one of the world's most endangered primates, with the goal of recommending management strategies. I systematically selected 31 forest fragments throughout the mangabey's 60-km distribution along the lower Tana River in southeastern Kenya. Within the 31 fragments, I measured vegetation structure, food abundance, and human forest product use in 107 belt transects, and conducted 370 mangabey surveys. I used a weighted multiple regression analysis to determine whether there was a dependence between the selected forest attributes and the mean number of mangabey groups per fragment. Fragment area and density of trees > or =10 cm diameter at breast height (DBH) were the only variables that significantly correlated with the variation in mangabey abundance. No additional variables were significant when the analysis was limited to forest fragments inside the Tana River Primate National Reserve (TRPNR) or to fragments outside the TRPNR. When I estimated the resources available before recent human forest product use by adding nonharvested and harvested variables, the total basal area of the top 15 food species became significant. This was only within the TRPNR, however. Management, therefore, should focus on increasing forest area, density of trees > or =10 cm DBH, and coverage of food trees throughout the mangabey's distribution. Solutions must be found for the problem of forest clearing, and forest product use must be better managed to protect the habitat of this critically endangered primate. The significance of food abundance only within the TRPNR suggests a need to collect dietary data from mangabey groups in fragments toward the southern limit of the mangabey's distribution, where plant species composition differs from that in fragments in which dietary data have been previously collected.