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"Red colobus monkey Behavior."
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A long‐term study on food choices and nutritional goals of a leaf‐eating primate
Efficient foraging plays a critical role in fitness, yet food choices and underlying nutritional goals vary among animals. To understand those choices and therefore the importance of different food resources, many studies estimate food preferences by applying electivity indices that account for resource availabilities. However, the general applicability of electivity indices in biologically relevant foraging scenarios is unclear. Our major aims were to find effective methods to estimate animals' food choices and to investigate long‐term food choices and underlying nutritional goals of the red colobus monkey (Piliocolobus tephrosceles) in Kibale National Park, Uganda, an endangered folivore. We used simulations of different foraging conditions to evaluate the applicability of electivity indices in biologically relevant scenarios to help interpret our results. Then, we used long‐term data collected between 2006 and 2016 on the feeding behavior and ecology of red colobus to determine the consumption frequencies of different foods and their food preferences. Based on these results and nutritional concentrations of young leaves of frequently consumed tree species, we investigated the importance of the protein‐to‐fiber ratio in their diet. Our simulations highlight limitations of electivity indices in biologically relevant foraging scenarios. Further, red colobus clearly chose young leaves over other plant parts, and, considering species and plant part, red colobus fed on many different items, but few dominated their diet. The availability and spatial distribution varied across the most consumed foods, but red colobus preferences remained mostly stable over time. Protein‐to‐fiber ratio had no association with preference but with consumption frequencies of different young leaves. The limitations of electivity indices in different foraging conditions underline the importance of comparing food preferences with consumption frequencies to assess the importance of different food resources. Our results provide a robust understanding of the food choices and nutritional goals of a leaf‐eating animal that can ultimately be used for implementing more effective conservation measures by directing habitat protection or restoration efforts toward these resources.
Journal Article
Longitudinal changes in the targets of chimpanzee (Pan troglodytes) hunts at Mahale Mountains National Park: how and why did they begin to intensively hunt red colobus (Piliocolobus rufomitratus) in the 1980s?
The hunting activities of chimpanzees (Pan troglodytes) at Mahale Mountains National Park exhibited a significant change over a 46-year observation period, shifting from sporadic hunting for small ungulates and primates through seizure or chasing, to a specialized hunting habit for red colobus (Piliocolobus rufomitratus). By the early 1980s, a new hunting habit had developed through the following stages: (1) occasional single kills by mature/adolescent males, (2) multiple kills by mature/adolescent males, (3) participation of mature females in both multiple and single kills, and (4) increased frequencies of multiple kills and female participation in killing. Throughout the observation period, red colobus was the most frequently hunted species, accounting for 71.0% of all hunts, 68.1% of all kills, and 70.3% of the consumed prey. Adult/adolescent female chimpanzees accounted for 23.1% of all kills and 20.4% of red colobus kills, both of which are higher than proportions reported in other areas. There are several possible explanations for these changes: (1) improved observation conditions, including familiarization of the chimpanzees with human observers; (2) environmental changes such as forest and faunal recovery, particularly an increase in the red colobus population; (3) change(s) in observation methods; (4) a new invention or (5) reinvention by the Mimikire (M) group chimpanzees; and (6) the change in intergroup relationships between the M and Kajabala (K) groups.
Journal Article
Using multiple travel paths to estimate daily travel distance in arboreal, group-living primates
Primate field studies often estimate daily travel distance (DTD) in order to estimate energy expenditure and/or test foraging hypotheses. In group-living species, the center of mass (CM) method is traditionally used to measure DTD; a point is marked at the group’s perceived center of mass at a set time interval or upon each move, and the distance between consecutive points is measured and summed. However, for groups using multiple travel paths, the CM method potentially creates a central path that is shorter than the individual paths and/or traverses unused areas. These problems may compromise tests of foraging hypotheses, since distance and energy expenditure could be underestimated. To better understand the magnitude of these potential biases, I designed and tested the multiple travel paths (MTP) method, in which DTD was calculated by recording all travel paths taken by the group’s members, weighting each path’s distance based on its proportional use by the group, and summing the weighted distances. To compare the MTP and CM methods, DTD was calculated using both methods in three groups of Udzungwa red colobus monkeys (
Procolobus gordonorum
; group size 30–43) for a random sample of 30 days between May 2009 and March 2010. Compared to the CM method, the MTP method provided significantly longer estimates of DTD that were more representative of the actual distance traveled and the areas used by a group. The MTP method is more time-intensive and requires multiple observers compared to the CM method. However, it provides greater accuracy for testing ecological and foraging models.
Journal Article
Towards an Ecological Solution to the Folivore Paradox: Patch Depletion as an Indicator of Within-Group Scramble Competition in Red Colobus Monkeys (Piliocolobus tephrosceles)
A number of socioecological models assume that within-group food competition is either weak or absent among folivorous primates. This assumption is made because their food resources are presumed to be superabundant and evenly dispersed. However, recent evidence increasingly suggests that folivore group size is food-limited, that the primates prefer patchily distributed high-quality foods, and display some of the expected responses to within-group scramble competition. To investigate this apparent contradiction between theoretical models and recent empirical data, we examined the foraging behaviour of red colobus monkeys (Piliocolobus tephrosceles) in Kibale National Park, Uganda. We found that red colobus monkeys foraged in a manner that suggests they deplete patches of preferred foods: intake rate slowed significantly during patch occupancy while movement rate, an index of foraging effort, increased. Furthermore, patch occupancy was related to the size of the feeding group and the size of the patch. These results suggest that within-group scramble competition occurs, may limit folivore group size, and should be considered in models of folivore behavioural ecology.
Journal Article
Increasing Group Size Alters Behavior of a Folivorous Primate
Group size influences many aspects of mammalian social life, including stress levels, disease transmission, reproductive rates, and behavior. However, much of what is known about the effects of group size on behavioral ecology has come from comparisons across multiple groups of different sizes. These findings may be biased because behavioral differences across groups may be more indicative of how environmental variation influences animal behavior, rather than group size itself. To partially circumvent this limitation, we used longitudinal data to examine how changes in group size across time affect the behavior of folivorous red colobus monkeys (
Procolobus rufomitratus
) of Kibale National Park, Uganda. Controlling for food availability, we demonstrated that increasing group size resulted in altered activity budgets, based on 6 yr of data on a group that increased from 57 to 98 members. Specifically, as group size increased, individuals spent less time feeding and socializing, more time traveling, and increased the diversity of their diet. These changes appear to allow the monkeys to compensate for greater scramble competition apparent at larger group sizes, as increasing group size did not show the predicted relationship with lower female fecundity. Our results support recent findings documenting feeding competition in folivorous primates. Our results also document behavioral flexibility, an important trait that allows many social mammals to maximize the benefits of sociality (e.g., increased vigilance), while minimizing the costs (e.g., increased feeding competition).
Journal Article
Hunting Behavior of Chimpanzees at Ngogo, Kibale National Park, Uganda
Chimpanzees (Pan troglodytes) prey on a variety of vertebrates, mostly on red colobus (Procolobus spp.) where the two species are sympatric. Variation across population occurs in hunting frequency and success, in whether hunting is cooperative, i.e., payoffs to individual hunters increase with group size, and in the extent to which hunters coordinate their actions in space and time, and in the impact of hunting on red colobus populations. Also, hunting frequency varies over time within populations, for reasons that are unclear. We present new data on hunting by chimpanzees at Ngogo, Kibale National Park, Uganda, and combine them with earlier data (Mitani and Watts, 1999, Am. J. Phys. Anthropol. 109: 439-454) to examine hunting frequency and success, seasonality, and cooperation. The Ngogo community is the largest and has the most males of any known community. Chimpanzees there mostly hunt red colobus and are much more successful and make many more kills per hunt than at other sites; they kill 6-12% of the red colobus population annually. The number of kills and the offtake of meat per hunt increase with the number of hunters, but per capita meat intake is independent of hunting party size; this suggests that cheating occurs in large parties. Some behavioral cooperation occurs. Hunting success and estimated meat intake vary greatly among males, partly due to dominance rank effects. The high overall success rate leads to relatively high average per capita meat intake despite the large number of consumers. The frequency of hunts and of hunting patrols varies positively with the availability of ripe fruit; this is the first quantitative demonstration of a relationship between hunting frequency and the availability of other food, and implies that the chimpanzees hunt most when they can easily meet energy needs from other sources. We provide the first quantitative support for the argument that variation in canopy structure influences decisions to hunt red colobus because hunts are easier where the canopy is broken.[PUBLICATION ABSTRACT]
Journal Article
Influence of Chimpanzee Predation on Associations Between Red Colobus and Red-tailed Monkeys at Ngogo, Kibale National Park, Uganda
Issue Title: Special Issue: Behavior, Ecology, and Conservation of Colobine Monkeys Colobines often associate with cercopithecines at various African sites. Such polyspecific associations presumably have an antipredation function. At Ngogo, Kibale National Park, Uganda, red colobus (Procolobus rufomitratus) spend considerable time in association with red-tailed monkeys (Cercopithecus ascanius), and they are also heavily hunted by chimpanzees (Pan troglodytes). I conducted behavioral observations and playback experiments to test the hypothesis that red colobus and red-tailed monkeys obtain mutual protection and predator-related benefits by associating. Despite high chimpanzee hunting pressure on red colobus and much lower hunting pressure on red-tailed monkeys, red-tailed monkeys initiate, maintain, and terminate the associations. The results suggest that rather than providing red colobus with protection against chimpanzees, the associations occur mostly because they protect red-tailed monkeys against predation by eagles.[PUBLICATION ABSTRACT]
Journal Article
Influence of chimpanzee predation on the red colobus population at Ngogo, Kibale National Park, Uganda
Frequent hunting of red colobus monkeys (
Procolobus rufomitratus
) takes place at all long-term chimpanzee (
Pan troglodytes
) study sites where both species are present. Red colobus are the most commonly selected prey of chimpanzees even when other monkey species are more abundant. In particular, the chimpanzee community at Ngogo, Kibale National Park, Uganda, preys heavily on red colobus monkeys: the chimpanzee hunting success rate is extremely high, and chimpanzees kill many individuals per successful hunt. Census data had suggested that the red colobus population is declining and that predation by chimpanzees may be contributing to this decline. In this paper, I address the impact of hunting on the red colobus population at Ngogo. To test the hypothesis that chimpanzee hunting is sustainable, I am using demographic data collected on red colobus monkeys over a period of 3 years, as well as fecundity and mortality data from previous studies of this species. I apply matrix models and vortex analyses using a sensitivity analysis approach to project future population development. Results show that current rates of hunting are not sustainable, but that chimpanzees are neither more “noble”, nor more “savage” than humans are, but that they also hunt to ensure maximum benefit without regard for the consequences for the prey population.
Journal Article
How adaptive or phylogenetically inert is primate social behaviour? A test with two sympatric colobines
Socio-ecological theories predict that females adapt their social behaviour to their environment. On the other hand, as a result of phylogenetic inertia, social behaviour may be slow to catch up when the environment changes. If social behaviour is adapted to the environment, competition and co-operation among females is predicted to reflect the characteristics of food sources. Contest competition both between and within groups is expected to result in alliances among related, philopatric, females. We compared social relationships and food characteristics of two sympatric and congeneric primate species, the red colobus and the black-and-white colobus of the Taï National Park, Ivory Coast. We found that affiliative interactions among females were comparable between the species. The differences in food characteristics could explain why black-and-white females competed more often than did red colobus females, both at the intra- and inter-group level. In contrast to socio-ecological theory, female inter-group aggression was not linked to female philopatry in black-and-white colobus. The species differed from each other and from other populations of the same or closely related species with respect to their inter-group behaviour which indicates that phylogenetic inertia did not constrain this aspect of social behaviour.
Journal Article