Implications of small scale variation in ecological conditions for the diet and density of red colobus monkeys

In this 3-year investigation we documented patterns of density, diet, and activity of red colobus monkeys (Procolobus tephrosceles) in six areas in or near Kibale National Park, Uganda and related these patterns to availability of food resources. There were large differences in the density and behavior of the red colobus among the sites. For example, the red colobus at one site with a diverse plant community of more than 61 tree species, had a diet that included at least 42 species. In contrast, at a second site red colobus spent 92% of their feeding time eating from one species that dominated the tree community. The density of important red colobus food trees varied among sites from 32 trees/ha to 204 trees/ha, and red colobus density ranged from 0.70 groups/km² to 7.41 groups/km². Among sites, red colobus density was related to the cumulative DBH of important food trees, when one apparently anomalous site was excluded, and populations with more plant species in their diets tended to be those that were found at higher densities. Activity budgets of the red colobus populations varied markedly among sites. For example, feeding time ranged among sites from 29 to 55%, and traveling varied from 5 to 20%. When faced with increased foraging demands, red colobus reduced the time spent resting, while the time spent socializing remained fairly constant. Comparative socioecological studies typically contrast species separated by large geographical distances to ensure there is sufficient variation in the environment to detect behavioral responses. The marked differences in ecological conditions and red colobus behavior we documented over short geographical distances, suggests that small-scale contrasts are a useful tool to examine ecological determinants of behavior and community structure.     

Effect of Group Size on Activity Budgets of Colobus vellerosus in Ghana

Group size influences foraging efficiency in several primates. We examined the activity budgets of 3 groups of Geoffroy's pied colobus (Colobus vellerosus) at the Boabeng-Fiema Monkey Sanctuary in Ghana to determine whether larger group size induces scramble competition. We studied 2 groups (B1; N = 7-8 and WW; N = 31-33) occupying slightly overlapping home ranges from August to November 2000. We observed the third group, B2 (N = 15-16), comprising B1 and 7 male invaders in the same home range as B1 from August to November 2001. By comparing groups belonging to the same population and occupying sligthly overlapping or similar home ranges, we were able to control, to a certain extent, for differences in food distribution. We recorded a total of 3353 scans, yielding 14,886 activity records, over 73 days. As with other black-and-white colobus, resting was their most common activity (59%). Intergroup comparisons suggest that time spent feeding, resting and moving did not vary in relation to group size. However, intragroup comparisons between the sexes show that females in the large group spent more time feeding than males did, whereas this was not the case in the small group, which suggests that scramble competition may be occurring among female Colobus vellerosus at BFMS. It is also possible that this may be due to greater nutritional requirements because of a higher proportion of infants in the large group. In fact, the proportion is quite similar between the two groups, lending support to the idea that females in the two groups had comparable nutritional demands due to lactation. This suggests that increased feeding in females in the large group was partly an effect of scramble competition. Group size and group composition also influenced the frequency of social behavior. There was more grooming in the large group, and it was performed mostly by females. The distribution of activities throughout the day was similar to the pattern reported for other black-and-white colobus.     

Population size and density of Colobus vellerosus at the Boabeng-Fiema Monkey Sanctuary and surrounding forest fragments in Ghana

The Boabeng-Fiema Monkey Sanctuary (BFMS) is inhabited by a growing population of Ursine colobus (Colobus vellerosus), a species that is listed as vulnerable. Smaller, degraded forest fragments that surround the BFMS also contain C. vellerosus and may provide an important habitat for the monkeys. Our objectives were to 1) determine the current population size and density of C. vellerosus at BFMS and in five surrounding fragments, 2) examine the differences in demographics between the fragments and BFMS, and 3) determine whether a relationship exists between population density and fragment size and isolation distance from BFMS. The census was a complete count and was conducted for 1 month (July 2003) by S.W. and trained research assistants. Seven census routes were walked simultaneously on 13 days. The 2003 population estimate of C. vellerosus at BFMS was 217-241 individuals (15 groups), a slight increase from the 2000 census. Numbers in the fragments (58-62, six groups) have remained stable since 1997, when the only other census of these fragments was conducted. Mean group size did not differ between the fragments and BFMS. Larger fragments had larger numbers of colobus, but there was no relationship between fragment size and colobus density. Isolation distance had no effect on population density. Our data suggest that colobus probably travel between fragments. Conservation efforts should focus on treating the small forests and their connecting areas as a single conservation unit.     

Predicting the Competitive Regime of Female <Emphasis Type="Italic">Colobus vellerosus</Emphasis> from the Distribution of Food Resources

We examined the spatial and temporal distribution of the foods of ursine colobus (Colobus vellerosus) at Boabeng-Fiema, Ghana as a means to predict the monopolizablity and usurpability of their food resources. Recent evidence suggests that food may not be limiting for folivorous primates, and that male sexual coercion may be a more important influence on folivore social organization. To address the question, we collected focal data on the feeding behavior of adult females and males over 11 mo (September 2000-August 2001) on 2 groups: WW (n = 31–33 individuals) and B (n = 8–16 individuals). We also conducted phenological monitoring and a tree survey of the two-group home ranges to establish food availability and distribution. We used 2 behavioral or organism-defined indicators of feeding behavior to assess potential resource contestability: food site residence time and distance moved between food sites. The colobus fed on a high diversity of species, most of their food trees were not clumped in distribution, within-tree interfood distances were short, and food trees were large. The only condition associated with the potential for monopolization was low food tree density. However, low food tree density may be offset by the colobus’ use of large trees. Taken together, the ecological and behavioral indicators suggest the food resources of Colobus vellerosus had a low potential for monopolization. Our results also indicate mature leaves had the longest food site residence time, which may suggest they should be the most usurpable plant part, though their presumed low quality and high abundance probably counteracted the effect. The pattern implied the potential for direct feeding competition among Colobus vellerosus at Boabeng-Fiema was low and agonistic interactions over food are not expected. Instead, a group size effect on feeding efficiency should be a more predominant influence on feeding efficiency, if food is limiting for the species.     

Ecology of the Zanzibar Red Colobus Monkey: Demographic Variability and Habitat Stability

We examined the Zanzibar red colobus' (Procolobus kirkii) social structure and population dynamics in relation to the density, diversity and dispersion of food resources in ground-water forest and agricultural land, which we characterized in terms of red colobus food species density, diversity, basal area and dispersion. We used transect sampling and group follows to describe population dynamics and social systems. Two agricultural areas, SJF Shamba and Pete Village, had higher densities and more uniformly dispersed red colobus food tree species than those of the ground-water forest. Red colobus at these two sites had greater population densities and natality, and smaller home ranges than red colobus in the ground-water forest. However, these findings apply to a very small area of agricultural land (approximately 18 ha) that is contiguous with an area of the forest reserve having a high density of red colobus. It is not representative of agricultural areas elsewhere on Zanzibar which support much lower densities or no red colobus. Although agricultural areas contiguous with the forest reserve had high densities of red colobus, they appear to be very unstable. Within the agricultural areas, we observed higher intergroup variation in group size and composition, study groups that decreased dramatically in size and disappeared from the study site, significantly lower levels of juvenile recruitment, and red colobus food trees that exhibited definite signs of overbrowsing. This apparent instability in the subpopulation of red colobus utilizing agricultural systems probably reflects the lower basal area of food trees and the greater fragmentation of suitable habitat and floristic dynamics due to human activities in these areas. A fusion-fission social system occurred only in the ground-water forest subpopulation, which we hypothesize to be due to highly clumped food resources.     

Effects of Forest Fragmentation on the Abundance of <Emphasis Type="Italic">Colobus angolensis palliatus</Emphasis> in Kenya’s Coastal Forests

We documented the occurrence and abundance patterns of Angola black-and-white colobus (Colobus angolensis palliatus) in 46 coastal forest fragments ranging from 1 ha to >1400 ha in the Kwale District, Kenya. In field surveys conducted in 2001, we also recorded forest spatial, structural, resource, and disturbance characteristics to determine the effects of habitat quality and fragmentation and the factors most critical to the continued survival of the little-known species. We tested 13 hypotheses to explain variation in patch occupancy and abundance patterns of Colobus angolensis palliatus in relation to habitat attributes. Minimal adequate models indicated that the occurrence of colobus in forest fragments is positively associated with fragment area and canopy cover, whereas the density of colobus in occupied fragments is attributable to forest area, the proportion of forest change over the previous 12 yr, and the basal area of 14 major food trees. Large-scale illegal extraction of major colobus food trees in the District for human resource use, in both protected and unprotected forests, together with ongoing forest clearance and modification, are the major threats to Colobus angolensis palliatus in Kenya.     

Diets of two sympatric colobines in Zaire: More evidence on seed-eating in forests on poor soils

Recent studies have shown that the so- called folivorous African colobines eat a significant amount of seeds. There is disagreement as to whether seed-eating is due to the poor quality of tree foliage, due in turn to poor soils, or to the fact that seeds are a normal part of colobine diets. To test these hypotheses, we studied feeding of red colobus monkeys, Colobus badius tholloni,and black-and-white colobus monkeys, Colobus angolensis angolensis,in a tropical rain forest of Central Zaire (Salonga National Park). We conducted studies on soil properties, vegetation composition, and the availability and chemical contents of food plants simultaneously. Soils were very acid, with a high percentage of sand, very low cation exchange capacity, and very low exchangeable bases. The forest was dominated by legumes (45.6% of trees), among which the Caesalpinioideae were the best represented (85%). C. badiusfed mostly on leaves (61%) and seeds (33%), legumes making up 65% of their diet. C. angolensisfed mostly on seeds (50%) and leaves (27%); 39% of their diet came from legumes. The two species tended to select items richer in crude protein or lipids or both. Total phenolics and condensed tannins were abundant in the foliage and seeds but were poor predictors of colobine choice of food. Intersite comparisons show that colobines in Zaire ate a higher proportion of seeds than all other related species so far studied in Africa and that the Salonga forest had among the poorest soils and harbored the highest percentage of Caesalpinioideae. Our results confirm that seed- eating is more common among colobines living in areas where soils are poor. They strongly suggest that this link is mediated through forest composition, especially the abundance of legumes, and that the development of seed- eating results both from the high availability of nutrient-rich seeds and from the poor quality of mature tree foliage.     

Coping with Forest Fragmentation: The Primates of Kibale National Park,Uganda

A goal of conservation biology is to determine which types of species are most susceptible to habitat disturbance and which types of disturbed habitats can support particular species. We studied 20 forest fragments outside of Kibale National Park, Uganda, to address this question. At each patch, we determined the presence of primate species, tree species composition, patch size, and distance to nearest patch. We collected demographic, behavioral, and dietary data for Abyssinian black-and-white colobus (Colobus guereza). Black-and-white colobus and red-tailed guenons (Cercopithecus ascanius) were in almost all fragments; Pennant's red colobus (Procolobus pennantii) and chimpanzees (Pan troglodytes) were in some fragments; and blue monkeys (Cercopithecus mitis) and gray-cheeked mangabeys (Lophocebus albigena) were absent from all fragments. No species characteristics—home range, body size, group size, or degree of frugivory—predicted the ability of species to live in patches. No characteristics of patches—area, distance to the nearest patch, distance to Kibale, or number of food trees present—predicted the presence of a particular species in a patch, but distance to Kibale may have influenced presence of red colobus. Black-and-white colobus group size was significantly smaller in the forest patches than in the continuous forest of Kibale. For a group of black-and-white colobus in one patch, food plant species and home range size were very different from those of a group within Kibale. However, their activity budget and plant parts eaten were quite similar to those of the Kibale group. The lack of strong predictive variables as well as differences between other studies of fragmentation and ours caution against making generalizations about primate responses to fragmentation.     

The role of phytochemistry in dietary choices of Tana River red colobus monkeys(Procolobus badius rufomitratus)

We conducted a phytochemical survey of tree species growing within the riverine forests of the Tana River National Primate Reserve in Kenya to understand better the feeding ecology of an endangered resident primate, the Tana River red colobus monkey (Procolobus badius rufomitratus).Young leaves, which make up a large percentage of this monkey's diet, are significantly higher in nitrogen and lower in acid detergent fiber than more abundant mature leaves are. Phenolic chemistry had little inhibitory effect on feeding by P. b. rufomitratus.Choice among tree species by P. b. rufomitratusappears to be influenced largely by leaf availability,once an acceptable threshold of nitrogen and fiber is reached When mature leaves are eaten, they selected species that are high in nitrogen and low in fiber. A significantly higher nitrogen content was found for the mature leaves of all leguminous versus nonleguminous tree species. Consequently, the availability of certain types of mature leaf species during periods of preferred food scarcity may prove critical to groups of Tana River red colobus monkeys.     

Group size in folivorous primates: ecological constraints and the possible influence of social factors

The ecological-constraints model assumes that food items occur in depletable patches and proposes that an increase in group size leads to increased day range due to more rapid patch depletion. Smaller groups become advantageous when an increase in travel costs is not repaid by an increase in energy gained or some other fitness advantage. On the other hand, we also know that group size can be influenced by social factors. Here we contrast the diet and group size of red colobus (Procolobus badius) and black-and-white colobus (Colobus guereza) in Kibale National Park, Uganda to consider how ecological and social factors are affecting their group sizes. Subsequently, we examine whether the insights gained from this detailed comparison can provide an understanding of why the social organization and group size of mantled howlers (Alouatta palliata) and black howlers (A. pigra) differ. Two groups of red colobus and two groups of black-and-white colobus were studied over 10 months. Red colobus groups were larger (48 and 24) than black-and-white colobus groups (9 and 6). The two groups of red colobus overlap home ranges with the two groups of black-and-white colobus; 75% and 95% of their home ranges were within red colobuss home range. There was a great deal of similarity in the plant parts eaten by the two species and both species fed primarily on young leaves (red colobus 70%, black-and-white colobus 76%). In terms of the actual species consumed, again there was a great deal of similarity between species. The average dietary overlap among months for the two neighboring groups of red colobus was 37.3%, while the dietary overlap between the red colobus and the black-and-white colobus group that had its home range almost entirely within the home range of the red colobus groups averaged 43.2% among months. If ecological conditions were responsible for the difference in group size between the two colobine species, one would expect the density of food trees to be lower in the home ranges of the black-and-white colobus monkeys, since they have the smaller group size. We found the opposite to be true. Both black-and-white colobus groups had more food trees and the cumulative size of those trees was greater than those in the red colobuss home ranges. We quantify how these differences parallel differences in mantled and black howlers. The average group size for mantled howlers was 12.9 individuals, and for black howlers it was 5.3 individuals. We explore possible social constraints, such as infanticide, that prevent black-and-white colobus and black howlers from living in large groups.This revised version was published online in April 2005 with corrections to the cover date of the issue.     

Densities of Two Frugivorous Primates with Respect to Forest and Fragment Tree Species Composition and Fruit Availability

Conservation of wildlife populations requires extensive knowledge of their habitat requirements, efficient methods to evaluate habitat quality, and an understanding of the value of fragments and edges. Kibale National Park, Uganda has areas that differ in the densities of 2 species of frugivorous monkeys—Cercopithecus mitis and Lophocebus albigena—including one on an edge and forest fragments outside the park that lack both species. We compared the basal area densities of important food trees with primate densities. The density of Cercopithecus mitis correlates most strongly with the basal area density of all types of food trees combined. The density of Lophocebus albigena does not correlate with the basal area densities of any category of food trees or with fruit availability. An index of their density—number of groups seen per km walked—correlates to fruit availability but with marginal significance. Lack of a relationship between the basal area densities of food trees and density of Lophocebus albigena may be the result of a mismatch in scale between the forest area measured and their large home ranges. We compared the unused area of forest to the other areas of the forest and the fragments and found it had higher basal area densities in all food tree categories for both species than the fragments and lower basal area densities of most categories than the other parts of the forest, indicating that the fragments are poor quality and would probably be unused even if dispersal were likely.     

Feeding ecology of the long-tailed macaque(Macaca fascicularis) in Kalimantan Tengah,Indonesia

I studied long- tailed macaque (Macaca fascicularis)feeding behavior and ecology as part of a larger behavioral ecological study at the Natai Lengkuas Station, Tanjung Puting National Park, Kalimantan Tengah, Indonesia. I collected data on feeding behavior via scan sampling of all visible individuals in the focal group (approximately 800 observation hours). I established vegetational plots and monitored them monthly to determine food availability and abundance. I found long- tailed macaques to be primarily frugivorous;leaves, flowers, insects and bark provided the remainder of the diet. They used at least 33 plant species as food sources, but >60% of the diet was provided by only 5 species. Based on previous vegetational analyses, these tree species were among the highest in relative density. However, selection ratios for 19 food species indicate that 13 of them were selected more often than expected. Long- tailed macaques appear to be selective feeders but can exploit a variety of food sources during periods of food scarcity.     

Seminomadic Ranging in a Population of Black Colobus (Colobus satanas) in Gabon and its Ecological Correlates

We observed ranging patterns in a black colobus population in the Forêt des Abeilles, Central Gabon. We compared the results with those for two other populations (Lopé Reserve in Central Gabon, Douala-Edéa in coastal Cameroun) in order to estimate the extent of specific variability in population structure and ranging behavior and to identify ecological factors influencing interpopulation differences. The mean number of monkeys in a group is 17, and all groups had a multimale structure. Home ranges were large, and the fact that they continued to increase with increasing number of observations indicated that the monkeys did not frequently resample their habitat. Ranging patterns varied according to the staple food consumed: distances travelled daily increased with increasing seed intake and decreased with increasing leaf intake. The ranging patterns of groups of Colobus satanas are seminomadic. Up to 6 or 7 groups shared the same space, and two group ranges could overlap by as much as 65–75%. Comparisons with the two populations previously studied showed that group size and group structure are broadly similar. At all three sites, black colobus were mainly seed eaters and ate large amounts of leaves in the season of fruit shortage. In the Forêt des Abeilles, however, group home ranges were much larger than at other sites, and this population had the lowest density. This is correlated with vegetation composition and with harshness of the main dry season. This colobus population appears limited by both recurring food shortage in the dry season and episodic periods of seed shortage resulting from irregular fruiting of the dominant family Caesalpiniaceae. Their seminomadic ranging would constitute the least costly strategy to cope with the low carrying capacity of their habitat.     

Constraints on Group Size in Red Colobus and Red-tailed Guenons: Examining the Generality of the Ecological Constraints Model

The ecological constraints model proposes that an increase in group size will increase intragroup feeding competition and thereby constrain group size. Although this model has received wide acceptance, tests of it are based only on a few studies of species that have similar ecological requirements and social organizations, and there are reasons to question the widespread acceptance of the assumptions underpinning it. Via a 2-year study, we explored determinants of group size in species that feed on markedly different types of foods: the folivorous red colobus (Procolobus pennantii) and the frugivorous/insectivorous red-tailed guenon (Cercopithecus ascanius). We established 4 study sites approximately 15 km apart in Kibale National Park, Uganda, to examine the relationship between average group size and food availability. In both species, we quantified interdemic variation in diet, density of food trees, rate of travel, and group size. Red colobus at all sites relied heavily on leaf resources (75.5%–86.9%), but fruit (6.4%–13.9%) and flowers (2.0%–13.9%) were important in some populations. In general, red-tailed guenons fed on fruit (35.7%–59.7%), insects (14.5%–17.6%), and young leaves (12.2%–32.8%), but the amount of time allocated to these foods varied among sites. Average monthly density of trees bearing food items ranged among sites from 45 to 79 trees/ha for red colobus and from 19.6 to 67.3 trees/ha for red-tailed guenons. For both species, rate of travel was similar among sites, with one exception for red colobus. Average red colobus group size varied among sites from 14 to 40 (28 groups counted). Red-tailed guenon group size varied among sites from 11 to 24 (16 groups counted). As predicted by the ecological constraints model, group size increased with food tree density across sites for both species.     

The status ofColobus polykomos dollmani Schwarz

The two West African black-and-white colobus taxa,Colobus polykomos andC. vellerosus, are distinct species. A supposedly intermediate subspecies,C. polykomos dollmani, is actually a hybrid swarm, in whichC. vellerosus genes greatly predominate. We propose a hypothesis to explain this situation.     

Competing pressures on populations: long-term dynamics of food availability,food quality,disease, stress and animal abundance

Despite strong links between sociality and fitness that ultimately affect the size of animal populations, the particular social and ecological factors that lead to endangerment are not well understood. Here, we synthesize approximately 25 years of data and present new analyses that highlight dynamics in forest composition, food availability, the nutritional quality of food, disease, physiological stress and population size of endangered folivorous red colobus monkeys (Procolobus rufomitratus). There is a decline in the quality of leaves 15 and 30 years following two previous studies in an undisturbed area of forest. The consumption of a low-quality diet in one month was associated with higher glucocorticoid levels in the subsequent month and stress levels in groups living in degraded forest fragments where diet was poor was more than twice those in forest groups. In contrast, forest composition has changed and when red colobus food availability was weighted by the protein-to-fibre ratio, which we have shown positively predicts folivore biomass, there was an increase in the availability of high-quality trees. Despite these changing social and ecological factors, the abundance of red colobus has remained stable, possibly through a combination of increasing group size and behavioural flexibility.     

Charcoal Consumption by Zanzibar Red Colobus Monkeys: Its Function and Its Ecological and Demographic Consequences

The Zanzibar red colobus monkey is the only primate, aside from humans, known to eat charcoal in the wild. All age classes and both sexes eat charcoal, but only those groups living in perennial gardens or near human dwellings do so. The habit appears to be transmitted from mother to offspring by imitation, but how it developed in the first place is unknown. Sources of charcoal include charred stumps, logs, and branches, as well as that produced in kilns by humans. These charcoals adsorb organic materials, such as phenolics, particularly well and, as a consequence, remove these compounds, which have the potential to be toxic or interfere with digestion or both. The extreme inertness of charcoal makes it an unlikely source of minerals to the colobus. We conclude that, by eating charcoal, monkeys living in gardens with a high density of food species dominated by exotic trees — Indian almond and mango — are able to exploit this abundant food resource that is high in total phenolic content much more effectively than in the absence of charcoal. The young leaves of these exotic tree species are also very high in protein and highly digestible. The benefits of charcoal eating are most likely due to the fact that charcoal adsorbs phenolics better than proteins. This may explain in large part why the birth rates and population densities of the colobus living in the Indian almond and mango habitat adjacent to the Jozani Forest are significantly higher than those in the ground-water forest. The population density of colobus in this small area is the highest ever recorded for a nonhuman anthropoid (700/km ² ). It may not, however, be a stable situation, as there are indications of higher levels of aggression, lower recruitment into the medium-juvenile size class, and overbrowsing.     

The diet of the capped langur (Presbytis pileata) in a moist deciduous forest in Bangladesh

Capped langurs (Presbytis pileata) in Madhupur National Park in north-central Bangladesh have an annual diet that is comprised largely of mature leaves (42% of 20,460 total feeding records). Among colobine monkeys, only some populations of red colobus (Procolobus badius) have a diet richer in mature leaves. New leaves (11%) and fruit (24%) are the other annually important dietary items. Seasonal breakdown of this diet, however, revealed that during the monsoon months of May through September theP. pileata diet is approximately 50% fruit, including pulpy ripe fruit. This is also the period of maximum fruit availability. Data on diet and food availability indicate that while capped langurs subsist on mature leaves during the dry season (80% of diet from November to March), they select fruit and new leaves and switch to these foods whenever they are available. These data support the hypothesis that the colobine feeding strategy is adapted to cope with seasonal food scarcity.     

How do differences in species and part consumption affect diet nutrient concentrations? A test with red colobus monkeys in Kibale National Park,Uganda

Within a primate species, diet can be highly variable in composition, even at small spatial scales within the same forest, or temporally, suggesting that primates use different plant species and parts to meet similar nutritional needs. To test whether such differences in the plant species and parts that primates eat affects the nutrient concentrations that they obtain, we observed feeding of seven groups of red colobus monkeys ( Procolobus rufomitratus) residing in Kibale National Park, Uganda. The different groups consumed mostly young leaves from many of the same plant species, but spent different amounts of time feeding on them. As protein and fibre are suggested to be important determinants of colobine food choice and abundance, we analysed multiple samples of 47 food species for protein and fibre. Despite the differences in the plant species and parts eaten, the protein and fibre concentrations for the seven red colobus groups were similar. Our results suggest that colobus monkeys eating diets with differing amounts of species and parts may ultimately receive similar concentrations of nutrients.     

Effects of habitat disturbance on the behavioral ecology and demographics of the Tana river red colobus (Colobus badius rufomitratus)

Annual surveys in 1985–1987 revealed that, since 1975, the total population of the Tana River red colobus (Colobus badius rufomitratus)declined by approximately 80%. An intensive study in 1986–1988 of two groups of colobus in the Tana River Primate National Reserve indicated that habitat disturbance from the changing river course and shifting agricultural practices were primarily responsible for the decline. Clearcutting around Mchelelo forest in the late 1960s compressed colobus populations to levels probably above the carrying capacity. Between 1975 and 1986 primate population density declined dramatically, the number of red colobus groups in Mchelelo forest decreased by half, and the size of the remaining group was greatly reduced. In 1986, there were fewer solitary colobus and small parties in the forest, harem male takeovers did not occur, infant survivorship increased, and demographic parameters generally had improved. The colobus groups in Mchelelo in 1973–1975, living at higher densities, showed different feeding and ranging behaviors than 1986–1988 groups. Range size was smaller in 1975, range overlap occurred, and a greater portion of the forest was used per day and per month. Mature leaves accounted for a much higher proportion of the diet. Time spent feeding and resting was the same in both studies. Social organization in predominantly one- male groups was maintained and adult and subadult females transferred between groups.