Behavioural responses of lion-tailed macaques (Macaca silenus) to a changing habitat in a tropical rain forest fragment in the Western Ghats, India

Terrestriality across the primate order: A review and analysis of ground use in primates

Terrestriality is relatively rare in the predominantly arboreal primate order. How frequently, and when, terrestriality appears in primate evolution, and the factors that influence this behavior, are not well understood. To investigate this, we compiled data describing terrestriality in 515 extant nonhuman primate taxa. We describe the geographic and phylogenetic distribution of terrestriality, including an ancestral state reconstruction estimating the frequency and timing of evolutionary transitions to terrestriality. We review hypotheses concerning the evolution of primate terrestriality and test these using data we collected pertaining to characteristics including body mass and diet, and ecological factors including forest structure, food availability, weather, and predation pressure. Using Bayesian analyses, we find body mass and normalized difference vegetation index are the most reliable predictors of terrestriality. When considering subsets of taxa, we find ecological factors such as forest height and rainfall, and not body mass, are the most reliable predictors of terrestriality for platyrrhines and lemurs.

Feeding ecology of free-ranging long-tailed macaques in East Java, Indonesia: Relationship with human food availability

Food availability is an important factor affecting the feeding strategies of animals. Primate species living in habitats with high human activity have the potential to employ unique strategies to utilize human food resources. This study describes the feeding ecology of provisioned free-ranging long-tailed macaques (Macaca fascicularis) inhabiting Alas Purwo National Park, East Java, Indonesia. The activity budgets, dietary compositions, vertical usage, and ranging patterns of macaques were recorded between October 2021 and March 2022, and their relationships with the number of visitors (a proxy of human food availability) were examined. The macaques consumed more human food (mean ± SD: 53.9 ± 25.6%) than natural food (43.8 ± 25.5%), followed by unidentified food (2.3 ± 6.3%). Human food has several effects on the behavioral ecology of macaques, including reduced movement and increased social activity in response to the number of visitors, decreased consumption of natural food, frequent use of the ground and subcanopy strata, and decreased home range when the number of visitors increases. Thus, the relative importance of human food has substantially changed the essential behavioral ecology of provisioned macaque troops. Understanding the behavioral plasticity of macaques, particularly their responses to anthropogenic effects, could guide and contribute to the formulation of conservation policies and management plans.

Behavioral responses to riparian and anthropogenic edge effects in mantled howler monkeys (Alouatta palliata) in a disturbed riverine forest

Fragmented forests contain natural edges, including riparian zones, and anthropogenic edges. Edges generally have lower plant density and fewer large trees than forest interior. Riparian edges, however, contain gap-specialist trees yielding leaves with high protein content, providing primates with important resources. We examined mantled howler monkeys' behavioral responses to riparian and anthropogenic edges at La Suerte Biological Research Station (LSBRS), Costa Rica. We predicted the monkeys would spend more time resting and feeding and less time traveling, and be less spatially cohesive, in both anthropogenic and riparian edges compared to forest interior due to lower resource abundance in edges, and in anthropogenic compared to riparian edge due to higher leaf quality in riparian zones. From 2017 to 2020, we collected data across forest zones on activity and spatial cohesion patterns via focal sampling, recording data every 2 min. Howler monkeys were significantly more likely to rest and significantly less likely to travel in both anthropogenic and riparian edges compared to forest interior; however, there were no differences between these edge types. There were significantly more monkeys within a 5-m radius of focal subjects in both anthropogenic and riparian edges compared to forest interior, but no differences between these edge types. While prior research found no differences across zones when only anthropogenic edge and forest interior were compared, results of this study demonstrate that howler monkeys at LSBRS modify their activity patterns in anthropogenic and riparian edge zones compared to forest interior, highlighting the importance of focusing on both natural and anthropogenic edge zones to fully understand primates' behavioral responses in fragmented landscapes.

Personality as a Predictor of Time-Activity Budget in Lion-Tailed Macaques (Macaca silenus)

Simple Summary

Time-activity budgets describe how animals divide their day into various behaviours and activities, e.g., time spent foraging or resting. Activity budgets can serve as crucial indicators of energy intake and expenditure, providing better knowledge of a species’ lifestyle. The conventional trend has been to explore group-level time-activity budgets; however, individuals may also vary in their time-activity budgets (e.g., one individual foraging more than another), with the influencing mechanisms still poorly understood. We propose that animal personality, a behavioural and cognitive profile that makes one individual different from another, may explain why individuals vary in their time-activity budgets. We used a multi-method approach comprised of behavioural observations and experiments to assess the personality traits of lion-tailed macaques. The observed traits were used to predict individual time-activity budgets, broadly categorised into food-related, active, and resting behaviours. We then discuss the significance of this novel approach in light of lion-tailed macaque ecology, conservation, and welfare.

Abstract

Time-activity budget, i.e., how a population or an individual divides their day into various behaviours and activities, is an important ecological aspect. Existing research primarily focused on group-level time-activity budgets, while individual variations have only been reported recently. However, little is known about how consistent inter-individual differences or personalities influence time-activity budgets. We examined the personalities of lion-tailed macaques (Macaca silenus) and investigated their influence on individual time-activity budgets. The resulting personality traits, namely persistence, sociability, affiliation, and anxiety, were used to predict the three broad categories of the time-activity budget—food-related, active, and resting behaviours. We found that persistence and sociability positively predicted the time spent being active. Food-related behaviours were positively predicted by persistence, while anxiety was found to influence them negatively. The time spent resting was negatively predicted by persistence. We did not find an effect of affiliation on the time-activity budgets. We discuss these findings in light of the ecology of lion-tailed macaques. Our study highlights the importance of a novel approach that uses animal personality traits as predictors of individual time-activity budgets and offers insights regarding the use of personality assessments in conservation and welfare activities.

Epidemiology of the zoonotic malaria Plasmodium knowlesi in changing landscapes

Within the past two decades, incidence of human cases of the zoonotic malaria Plasmodium knowlesi has increased markedly. P. knowlesi is now the most common cause of human malaria in Malaysia and threatens to undermine malaria control programmes across Southeast Asia. The emergence of zoonotic malaria corresponds to a period of rapid deforestation within this region. These environmental changes impact the distribution and behaviour of the simian hosts, mosquito vector species and human populations, creating new opportunities for P. knowlesi transmission. Here, we review how landscape changes can drive zoonotic disease emergence, examine the extent and causes of these changes across Southeast and identify how these mechanisms may be impacting P. knowlesi dynamics. We review the current spatial epidemiology of reported P. knowlesi infections in people and assess how these demographic and environmental changes may lead to changes in transmission patterns. Finally, we identify opportunities to improve P. knowlesi surveillance and develop targeted ecological interventions within these landscapes.

Feeding ecology and diet of the southern geladas (Theropithecus gelada obscurus) in human-modified landscape, Wollo, Ethiopia

Studying the dietary flexibility of primates that live in human-modified environments is crucial for understanding their ecological adaptations as well as developing management and conservation plans. Southern gelada (Theropithecus gelada obscurus) is an endemic little-known subspecies of gelada that inhabits human-modified landscapes in the northern central highlands of Ethiopia. During an 18-month period, we conducted this intensive study in an unprotected area of a human-modified landscape at Kosheme in Wollo to investigate the feeding ecology of southern geladas and their dietary responses to seasonal variations. We quantified the monthly and seasonal diet data from a band of southern geladas using instantaneous scan sampling method at 15-min intervals, and green grass phenology and availability using visual inspection from the randomly selected permanent plots. The overall average diet of southern geladas at Kosheme constituted grass blades 55.4%, grass undergrounds 13.2%, grass bulbs 5.6%, grass seeds 5.4%, herb leaves 4.0, fruits 7.3%, and cereal crops 5.6%. Grass blade consumption increased with increasing green grass availability, while underground food consumption increased with decreasing green grass availability, and vice versa. Southern geladas spent significantly more time feeding on the grass blades and herb leaves and significantly less time on bulbs during the wet season than the dry season. Underground grass items (rhizomes and corms) were not consumed during the wet season, but made up 22.3% of the dry season diet. Thus, although grass blades are staple diet items for geladas, underground diet items are important "fallback foods" at Kosheme. Our result shows insights into the dietary flexibility southern geladas adopt to cope with human-modified landscapes of the north-central Ethiopian Highlands. Thus, the study contributes to a better understanding of how changing environments shape primate ecology and evolution.

Changing ecologies, shifting behaviours: Behavioural responses of a rainforest primate, the lion-tailed macaque Macaca silenus, to a matrix of anthropogenic habitats in southern India

With the uncontrolled expansion of anthropogenic modifications of the environment, wildlife species are forced to interact with humans, often leading to conflict situations that have detrimental effects for both wildlife and humans. Such interactions are escalating globally, making it crucial for us to devise strategies for both, the management of conflict and the conservation of these often-threatened species. We studied a case of potentially detrimental human-wildlife interactions between an endemic, habitat-specialist primate, the lion-tailed macaque Macaca silenus and resident human communities that has developed in recent years in the Western Ghats mountains of southern India. Primates provide useful model systems to understand the extent and nature of behavioural changes exhibited by wildlife in response to anthropogenic habitats with varying degrees of human influence. We documented behaviours, including foraging and intra-species social interactions, to examine the decisions made by the macaques as they exploited four human-modified habitats, which, for the purpose of this study, have been qualitatively characterised to include structural features of the habitat, type of food resources available and the presence of humans. Access to human-origin food, either cooked or packaged, acquired directly from homes or garbage pits, in the human-dominated habitat appeared to significantly reduce active foraging and searching for food, allowing them to engage in other behavioural activities, such as resting. Furthermore, patterns of reciprocated affiliation dissipated in certain human-dominated habitats, with individuals seeming to have adopted novel behavioural strategies, leading to altered social dynamics in the troop, possibly in response to provisioning. This study thus highlights the importance of understanding behavioural changes displayed by animals in response to human interactions; such knowledge could be crucial for the planning and implementation of management and conservation strategies for endangered species such as the lion-tailed macaque and possibly other wildlife in the increasingly anthropogenic landscapes of the tropical world.

Forest fragments become farmland: Dietary Response of wild chimpanzees (Pan troglodytes) to fast-changing anthropogenic landscapes

Behavioral flexibility, including an ability to modify feeding behavior, is a key trait enabling primates to survive in forest fragments. In human-dominated landscapes, unprotected forest fragments can become progressively degraded, and may be cleared entirely, challenging the capacity of primates to adjust to the changes. We examined responses of wild chimpanzees (Pan troglodytes schweinfurthii) to major habitat change: that is, clearance of forest fragments for agriculture. Over 7 years, fragments in Bulindi, Uganda, were reduced in size by 80%. We compared the chimpanzees' diet at the start and end of this period of rapid deforestation, using data derived mainly from fecal analysis. Similar to other long-term study populations, chimpanzees in Bulindi have a diverse diet comprising over 169 plant foods. However, extensive deforestation seemed to impact their feeding ecology. Dietary changes after fragment clearance included reduced overall frugivory, reduced intake of figs (Ficus spp.; formerly a dietary "staple" for these chimpanzees), and reduced variety of fruits in fecal samples. Nevertheless, the magnitude of most changes was remarkably minor given the extent of forest loss. Agricultural fruits increased in dietary importance, with crops accounting for a greater proportion of fruits in fecal samples after deforestation. In particular, cultivated jackfruit (Artocarpus heterophyllus) became a "staple" food for the chimpanzees but was scarcely eaten before fragment clearance. Crops offer some nutritional benefits for primates, being high in carbohydrate energy and low in hard-to-digest fiber. Thus, crop feeding may have offset foraging costs associated with loss of wild foods and reduced overall frugivory for the chimpanzees. The adaptability of many primates offers hope for their conservation in fragmented, rural landscapes. However, long-term data are needed to establish whether potential benefits (i.e. energetic, reproductive) of foraging in agricultural matrix habitats outweigh fitness costs from anthropogenic mortality risk for chimpanzees and other adaptable primates.

Primate Infectious Disease Ecology: Insights and Future Directions at the Human-Macaque Interface

Global population expansion has increased interactions and conflicts between humans and nonhuman primates over shared ecological space and resources. Such ecological overlap, along with our shared evolutionary histories, makes human-nonhuman primate interfaces hot spots for the acquisition and transmission of parasites. In this chapter, we bring to light the importance of human-macaque interfaces in particular as hot spots for infectious disease ecological and epidemiological assessments. We first outline the significance and broader objectives behind research related to the subfield of primate infectious disease ecology and epidemiology. We then reveal how members of the genus Macaca, being among the most socioecologically flexible and invasive of all primate taxa, live under varying degrees of overlap with humans in anthropogenic landscapes. Thus, human-macaque interfaces may favor the bidirectional exchange of parasites. We then review studies that have isolated various types of parasites at human-macaque interfaces, using information from the Global Mammal Parasite Database (GMPD: http://www.mammalparasites.org/). Finally, we elaborate on avenues through which the implementation of both novel conceptual frameworks (e.g., Coupled Systems, One Health) and quantitative network-based approaches (e.g., social and bipartite networks, agent-based modeling) may potentially address some of the critical gaps in our current knowledge of infectious disease ecology at human-primate interfaces.

Ecological fragmentation effects in mouse lemurs and small mammals in northwestern Madagascar

Habitat loss and fragmentation are major ecological forces threatening animal communities across the globe. These issues are especially true in Madagascar, where forest loss is ongoing. We examined the effects of forest fragmentation on the distribution and abundance of sympatric, endemic gray, and golden-brown mouse lemurs (Microcebus murinus and Microcebus ravelobensis), the endemic western tuft-tailed rat (Eliurus myoxinus), and the invasive black rat (Rattus rattus) in two regions in northwestern Madagascar. We used systematic capture procedures in 40 forest fragments and four continuous forest sites which differed in size, shape, and degree of isolation. With a trapping effort of 11,567 trap nights during two dry seasons (2017-2018), we captured 929 individuals (432 M. ravelobensis, 196 M. murinus, 116 E. myoxinus, and 185 R. rattus). We examined the influence of study region, forest type (fragment vs. continuous), forest size, forest shape, the proportion of 50-m forest edge and distance to continuous forest on the abundance and interaction of the four species. Responses to fragmentation differed strongly between species, but no interaction could be detected between the abundance of the different species. Thus competition within and between native and invasive species may not be regulating abundances in these regions. On the contrary, the abundance of M. ravelobensis and E. myoxinus differed significantly between study regions and was negatively affected by fragmentation. In contrast, there was no evidence of an impact of fragmentation on the abundance of M. murinus. Finally, the invasive R. rattus responded positively to the increasing distance to the continuous forest. In conclusion, the response of small Malagasy mammals to forest fragmentation varies largely between species, and fragmentation effects need to be examined at a species-specific level to fully understand their ecological dynamics and complexity.

Prevalence of gastrointestinal parasites in lion-tailed macaque Macaca silenus in central Western Ghats, India

This study examines gastrointestinal parasites in the endangered lion-tailed macaque, which is sympatric with the bonnet macaque that has relocated from nearby towns or agriculture landscapes dominated by humans and livestock. One hundred and ninety-four fresh fecal samples from lion-tailed macaques were collected from a group located at Chiksuli in the central Western Ghats. Of these, 48.5% had at least one endoparasite taxon. The prevalence of endoparasites varied from 0 to 75.0%, and observed endoparasite taxa varied between 0 and 10 across different months. The prevalence of endoparasites decreased with increasing rainfall and with increasing average maximum temperature across months. Of the 17 endoparasite taxa, 11 were nematodes, two were cestodes, and four were protozoans. The prevalence of Ascaris sp. and Entamoeba coli was higher than the other taxa. The overall load, helminth load, and protozoan load did not differ between months. The overall endoparasite load was greater in immature macaques in all seasons. Helminth load was higher in adult males, especially in the summer. Comparing our findings with those from sympatric relocated bonnet macaques of Chiksuli (Kumar et al. in PLoS ONE 13(11):e0207495, 2018) and lion-tailed macaques of Anamalai Hills (Hussain et al. in PLoS ONE 8(5):e63685, 2013) revealed: (a) a much higher prevalence of endoparasites in lion-tailed macaques from fragments of Anamalai Hills than in lion-tailed and bonnet macaques of Chiksuli; (b) higher richness of endoparasites in both macaque species of Chiksuli than in Anamalai lion-tailed macaques; and (c) more similar composition of endoparasite taxa between the Chiksuli lion-tailed and bonnet macaques than with the Anamalai Hills lion-tailed macaques. We suggest a complete cessation of relocation of commensal animals to the wild habitat. If relocation is necessary, then individuals to be relocated should be thoroughly screened and treated to prevent transferring endoparasite infections to wild populations.

Activity and Habitat Use of Chimpanzees (Pan troglodytes verus) in the Anthropogenic Landscape of Bossou, Guinea, West Africa

Many primate populations inhabit anthropogenic landscapes. Understanding their long-term ability to persist in such environments and associated real and perceived risks for both primates and people is essential for effective conservation planning. Primates in forest-agricultural mosaics often consume cultivars to supplement their diet, leading to potentially negative encounters with farmers. When crossing roads, primates also face the risk of encounters with people and collision with vehicles. Chimpanzees (Pan troglodytes verus) in Bossou, Guinea, West Africa, face such risks regularly. In this study, we aimed to examine their activity budget across habitat types and the influence of anthropogenic risks associated with cultivated fields, roads, and paths on their foraging behavior in noncultivated habitat. We conducted 6-h morning or afternoon follows daily from April 2012 to March 2013. Chimpanzees preferentially used forest habitat types for traveling and resting and highly disturbed habitat types for socializing. Wild fruit and crop availability influenced seasonal habitat use for foraging. Overall, chimpanzees preferred mature forest for all activities. They showed a significant preference for foraging at >200 m from cultivated fields compared to 0-100 m and 101-200 m, with no effect of habitat type or season, suggesting an influence of associated risk. Nevertheless, the chimpanzees did not actively avoid foraging close to roads and paths. Our study reveals chimpanzee reliance on different habitat types and the influence of human-induced pressures on their activities. Such information is critical for the establishment of effective land use management strategies in anthropogenic landscapes.

Plasmodium knowlesi transmission: integrating quantitative approaches from epidemiology and ecology to understand malaria as a zoonosis

The public health threat posed by zoonotic Plasmodium knowlesi appears to be growing: it is increasingly reported across South East Asia, and is the leading cause of malaria in Malaysian Borneo. Plasmodium knowlesi threatens progress towards malaria elimination as aspects of its transmission, such as spillover from wildlife reservoirs and reliance on outdoor-biting vectors, may limit the effectiveness of conventional methods of malaria control. The development of new quantitative approaches that address the ecological complexity of P. knowlesi, particularly through a focus on its primary reservoir hosts, will be required to control it. Here, we review what is known about P. knowlesi transmission, identify key knowledge gaps in the context of current approaches to transmission modelling, and discuss the integration of these approaches with clinical parasitology and geostatistical analysis. We highlight the need to incorporate the influences of fine-scale spatial variation, rapid changes to the landscape, and reservoir population and transmission dynamics. The proposed integrated approach would address the unique challenges posed by malaria as a zoonosis, aid the identification of transmission hotspots, provide insight into the mechanistic links between incidence and land use change and support the design of appropriate interventions.

Are interspecific associations of primates in the Western Ghats a matter of chance? A case study of the lion-tailed macaque

When animals or groups of animals in their wild habitats come close to each other within a defined distance, it is termed as an association. Observing two groups of the lion-tailed macaque at Nelliyampathy and Andiparai forests of the Western Ghats of India, we asked whether the lion-tailed macaque associations with the sympatric Nilgiri langur and bonnet macaque were by chance or had any biological significance. Employing ‘all occurrences’ sampling, we recorded an association if a group of another primate species came within 30 m of the focal group of the lion-tailed macaque. Date, time, associating species, activity of the study species and of the associating species, type of interaction, aggressor and the recipient, species displaced and duration of the association were recorded. We used the Waser gas model to calculate the expected frequency and duration of associations and compared them with the observed associations. The lion-tailed macaque spent less time in associations than expected. The lion-tailed macaque and the Nilgiri langur initiated associations less often, and remained in association for less time, than expected by chance. Whereas the expected and observed initiation of associations between the lion-tailed macaque and the Nilgiri langur in Nelliyampathy was significantly different (expected rate = 153; observed rate = 64), in Andiparai, it was not (expected rate = 55.5; observed rate = 61). The expected and observed association duration was significantly different in Nelliyampathy (expected duration = 54 min; observed duration = 15 min) and Andiparai (expected duration = 48 min; observed duration = 19 min). In contrast, we detected few differences between observed and expected association frequency for the lion-tailed macaque and the bonnet macaque. Aggressive interactions were common in areas where density of the Nilgiri langur groups was high. This is the first study on Asian primates using the ideal gas approach to show that primates do not form active associations with each other.

Nearest-neighbour clusters as a novel technique for assessing group associations

When all the individuals in a social group can be easily identified, one of the simplest measures of social interaction that can be recorded is nearest-neighbour identity. Many field studies use sequential scan samples of groups to build up association metrics using these nearest-neighbour identities. Here, I describe a simple technique for identifying clusters of associated individuals within groups that uses nearest-neighbour identity data. Using computer-generated datasets with known associations, I demonstrate that this clustering technique can be used to build data suitable for association metrics, and that it can generate comparable metrics to raw nearest-neighbour data, but with much less initial data. This technique could therefore be of use where it is difficult to generate large datasets. Other situations where the technique would be useful are discussed.

Resource partitioning in sympatric langurs and macaques in tropical rainforests of the central Western Ghats, south India

In a competitive sympatric association, coexisting species may try to reduce interspecific interactions as well as competition for similar resources by several ecological and behavioral practices. We studied resource utilization of three sympatric primate species namely, lion-tailed macaques (Macaca silenus), bonnet macaques (M. radiata) and Hanuman langurs (Semnopithecus entellus) in a tropical rainforest of the central Western Ghats, south India. We studied resource use, tree-height use, foraging height, substrate use when consuming animal prey and interspecific interactions. The results revealed that across the year, there was very limited niche overlap in diet between each species-pair. Each primate species largely depended on different plant species or different plant parts and phenophases from shared plant species. Primate species used different heights for foraging, and the two macaque species searched different substrates when foraging on animal prey. We also recorded season-wise resource abundance for the resources shared by these three primate species. While there was low dietary overlap during the dry season (a period of relatively low resource abundance), there was high dietary overlap between the two macaque species during the wet season (a period of high resource abundance for the shared resources). We observed only a few interspecific interactions. None of these were agonistic, even during the period of high niche overlap. This suggests that the sympatric primate species in this region are characterized by little or no contest competition. Unlike in some other regions of the Western Ghats, the lack of interspecific feeding competition appears to allow these primates, especially the macaques, to remain sympatric year-round.

Living in forest fragments reduces group cohesion in diademed sifakas (Propithecus diadema) in eastern Madagascar by reducing food patch size

Forest fragmentation is thought to threaten primate populations, yet the mechanisms by which this occurs remain largely unknown. However, fragmentation is known to cause dietary shifts in several primate species, and links between food resource distribution and within-group spatial dynamics are well documented. Thus, fragmentation has the potential to indirectly affect spatial dynamics, and these changes may present additional stresses to fragmented populations. I present the results from a 12-month study of Propithecus diadema at Tsinjoarivo, eastern Madagascar, including two groups in fragments and two in continuous forest. Instantaneous data on activity and spatial position were collected during all-day focal animal follows. Fragment groups had much lower cohesion, being more likely to have no neighbor within 5 and 10 m. For continuous forest groups, cohesion was highest in the rainy season (when food patches are large) and lowest in winter (when the animals rely on small-crowned mistletoes), and the chance of having no neighbor within 5 m was positively correlated with mistletoe consumption. Thus their decreased cohesion in fragment groups is inferred to result from their increased reliance on mistletoes and other small resources, which causes them to spread out among multiple patches. This scenario is consistent with the reduced body mass of subordinate individuals (males and immatures) in fragments, and suggests the occurrence of steeper within-group fitness gradients. Further research is necessary to determine whether these patterns apply to other primates; however, since fragmentation tends to cause the loss of the largest trees, many primates in fragments may lose their largest food resources and undergo similar behavioral shifts.

Population dynamics of a group of lion-tailed macaques (Macaca silenus) inhabiting a rainforest fragment in the Western Ghats, India

We observed the overall population dynamics and number of births and deaths in identified individuals between January 2002 and October 2005, in a large group of lion-tailed macaques in the Anaimalai Hills of the Western Ghats in the south Indian state of Tamilnadu. The group inhabited an isolated rainforest fragment located inside a private tea/coffee garden. The group size increased from 56 in January 2002 to 84 in October 2005. All females reproduced, and the interbirth interval was 23.18 months. Of the 37 infants born between 2002 and 2005, only 1 died providing an infant survivorship rate of about 97.3%. Although births occurred in all months, most of the infants were born between February and March, and this pattern of births was consistent over the years, indicating a major birth peak in this species. The population growth rate in this unusually large group was found to be higher than even in those groups of lion-tailed macaques that inhabit large and relatively undisturbed rainforest complexes. This high growth rate could be attributed to the availability of abundant cultivated fruit plants including commercial crops such as coffee seeds. The observations provide a perspective for the management of other groups of this endangered species inhabiting rainforest fragments.

Dominance hierarchy and social grooming in female lion- tailed macaques (Macaca silenus) in the Western Ghats, India

This article reports the structure of dominance and its relationship with social grooming in wild lion-tailed macaque females. The strength of dominance hierarchy was 0.79 on a scale of 0 to 1 indicating a moderate linearity in the ranking system. Dominance scores were converted into an ordinal as well as an interval scale. Grooming scores were also converted into interval scales using standard scores. Grooming received and grooming given correlated positively and negatively respectively with dominance ranks indicating that high ranking females received more and gave less grooming. Grooming was also positively related to encounter rates for dyads of females. More grooming among adjacent ranks, and grooming being more reciprocal, occurred only in the case of dominant females. The grooming patterns, therefore, appeared to be more of despotic than egalitarian nature. While ranking macaques into different Grades of social systems ranging from despotic to egalitarian, Thierry (2004) has placed lion-tailed macaques in Grade 3 corresponding to the 'relaxed' social system. Our results indicate that the grooming and dominance relationships in this species are more despotic, and hence, the Grade for this species requires to be shifted toward 2 or 1.

Comparison of habitat quality and diet of Colobus vellerosus in forest fragments in Ghana

The forest fragments surrounding the Boabeng-Fiema Monkey Sanctuary (BFMS) in central Ghana shelter small populations of Colobus vellerosus. Little is known about these populations or the ability of the fragments to support them, despite the fact that these fragments represent potentially important habitat for the colobus in this region. We compared the diet of three groups of C. vellerosus in the fragments to two groups in BFMS. We also examined the differences in plant species composition and food abundance among fragments. The study took place from June to November 2003. Dietary data were collected using scan sampling. Plant species composition and food abundance were evaluated using tree plots and large tree surveys. As in BFMS groups, leaves constituted the highest proportion of the diet of fragment groups, yet the colobus in fragments fed on more lianas than did those in BFMS. Over 50% of all species observed eaten by colobus in the fragments were not consumed in BFMS groups during the same season. Food abundance was similar between fragments and BFMS, although species composition differed. There was no relationship between the density of colobus and the density of food trees or percentage of food species, suggesting that other factors may be influencing the number of colobus present. This study highlights the broad dietary range of C. vellerosus, which may be a factor allowing its survival in these fragments.

Population size and density ofColobus 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.

Visual information processing in the lion-tailed macaque (Macaca silenus): mental rotation or rotational invariance?

Mental rotation is a widely accepted concept indicating an image-like mental representation of visual information and an analogue mode of information processing in certain visuospatial tasks. In the task of discriminating between image and mirror-image of rotated figures, human reaction times increase with the angular disparity between the figures. In animals, tests of this kind yield inconsistent results. Pigeons were found to use a time-independent rotational invariance, possibly indicating a non-analogue information processing system that evolved in response to the horizontal plane of reference birds perceive during flight. Despite similar ecological demands concerning the visual reference plane, a sea lion was found to use mental rotation in similar tasks, but its processing speed while rotating three-dimensional stimuli seemed to depend on the axis of rotation in a different way than found for humans in similar tasks. If ecological demands influence the way information processing systems evolve, hominids might have secondarily lost the ability of rotational invariance while retreating from arboreal living and evolving an upright gait in which the vertical reference plane is more important. We therefore conducted mental rotation experiments with an arboreal living primate species, the lion-tailed macaque. Performing a two-alternative matching-to-sample procedure, the animal had to decide between rotated figures representing image and mirror-image of a previously shown upright sample. Although non-rotated stimuli were recognized faster than rotated ones, the animal's mean reaction times did not clearly increase with the angle of rotation. These results are inconsistent with the mental rotation concept but also cannot be explained assuming a mere rotational invariance. Our study thus seems to support the idea of information processing systems evolving gradually in response to specific ecological demands.

Distribution, population structure, and conservation of lion-tailed macaques (Macaca silenus) in the Anaimalai Hills, Western Ghats, India

The lion-tailed macaque is an endangered species, and hence it is necessary that the remaining populations in the rainforests of the Western Ghats, India, be located and their habitats assessed for effective conservation. The Anaimalai Hills in the state of Tamil Nadu harbor 31 groups of lion-tailed macaques. However, the rainforest in these hills is highly fragmented. Since lion-tailed macaques are typically arboreal, the groups have become isolated. Two large rain-forest complexes in these hills harbor 12 and seven groups, respectively, and the remaining 12 groups inhabit small, isolated forest fragments. Group size ranges from six to 53 individuals, with a mean size of 16.3. In the small forest fragments, the standard deviation (SD) of group size was considerably higher than it was in the larger forest complexes. The disturbed fragments also had a higher variability in group size than the relatively undisturbed habitats. It is believed that fragmentation may impede male migration. We suggest that the fragments be managed in such a way that male migration among groups can be facilitated to overcome the potential effects of isolation.