Demography, Diet and Range Size in a Population of Black-handed Spider Monkey's

The International Primatological Society (IPS) congress takes place every two years, and this year was in Kyoto, Japan. As the name suggests, this conference brings together primate researchers from around the globe and promotes the dissemination and discussion of current research via a combination of plenary speakers, symposia, and oral and poster sessions over a week-long period. Abstracts are reviewed and published in conference proceedings, and all presentations are meant to elicit discussion and commentary. This year, I presented pilot data from a new study site I have initiated in Belize using RIG funding. I co-authored this presentation with a research colleague at the University of Calgary, who is also one of the PIs at our site. We currently co-supervise 2 graduate students working at the site, and both students presented posters at the IPS congress. I was a co-author one both posters. One of the posters (Kayla Hartwell’s poster on sex segregation) won second place in the student competition. In addition, as these students were masters students, this was their first international conference, and I played an important role in facilitating their connecting to other researchers in the discipline. In general, the conference was a success for all of us (me and my graduate students). We have been encouraged to continue our work on sex segregation, and indeed this has become the focus of Kayla’s upcoming PhD research.#1 Studies of wild Ateles geoffroyi yucatensis have occurred, or are ongoing in Mexico, Guatemala and Costa Rica, but no sites have been established in Belize. Across study sites, group composition, average sub-group size, diet and ranging patterns vary as a function of ecological and demographic variables particular to respective locations. Here we describe the age and sex compositions, average sub-group sizes, range sizes, activity budgets and diets of two recently habituated groups of spider monkeys at Runaway Creek Nature Preserve in Belize. Habituation and data collection began in June 2007 using a combination of all occurrences recording and group scans. Two separate and adjacent monkey groups were identified – Groups 1 and 2 – numbering 33 and 31 individuals respectively. Range sizes for both groups were determined using a minimum convex polygon of GPS location points. Group 1 ranged over an area of 114.43 ha (N=678) and Group 2 over 193.67 ha (N=181). Average sub-group size for all individuals of all age/sex classes in Group 1 group was 5.16 individuals, with a mode of 2 (N=415). In Group 2, average sub-group size was 4.48 individuals, with a mode of 3 (N=106). Between June 2007 and July 2009 the spider monkeys from both groups were observed feeding from 70 different plant species. These and future data emanating from this new study site represent an important addition to a small but growing number of studies that will further our understanding of within-species variability in response to differing socio-ecological variables across the range of Ateles. #2 Infant handling by adults other than the mother occurs to varying degrees across primate species and social organizations. Among males infant handling may reflect kinship-based affiliation, bond formation or a reproductive strategy that facilitates access to the mother. Spider monkeys (Ateles spp.) exhibit male philopatry and therefore males may preferentially handle male infants as they could be potential future allies. To investigate this hypothesis, all occurrence data were collected from January 2007 to December 2009 on a community of 35 wild spider monkeys at Runaway Creek Nature Reserve, Belize. During 555 hours of observation, 59 infant handling bouts and 12 infant handling attempts were recorded. All of the 11 infants were handled by individuals other than the mother during the study period. Handling of infants by adult, sub-adult and large juvenile males was the most common [N=48, or 81% of all bouts]. Infant handling by adult, sub-adult and large juvenile females was less common [N=11, or 19% of all bouts], but a higher proportion of handling bouts by females resulted in prolonged infant carries [0.36 for females; 0.10 for males]. Individual adult and sub-adult males varied with respect to their probability of handling an infant [Pearson X2=14.25, df=4, p<0.05]. The sex of the infant did not affect how often it was handled by males [Pearson X2=3.84, df=1, p=0.36]. As all infants born in a male philopatric group are presumed to share some degree of paternal kinship, we suggest that male infant handling in A. geoffroyi reflects kinship-based affiliation or tolerance. #3 Sexual segregation, the social and/or spatial separation of males and females, has been characterized in many animals; however, no systematic analysis has yet been undertaken to measure sex segregation in primates. Using data from a 7-month study on a community of spider monkeys in Belize, we used the Sexual Segregation Aggregation Statistic (SSAS) to determine if the sexes segregate or aggregate. We then determined if the patterns are driven by social, habitat, or reproductive differences between males and females. SSAS values range from 0 (complete aggregation) to 1 (complete segregation). The overall SSAS value suggests that male and female spider monkeys are slightly more segregated (SSAS=0.56) than aggregated. However segregation varies monthly; there is more segregation during the dry season months (January-April: 0.66-0.85) and more aggregation during the wet season months (May-July: 0.27-0.45). Several hypotheses have been proposed to explain the causes of segregation, such as the forage selection and predation risk hypotheses for habitat segregation and the social preferences and activity budget hypotheses for social segregation. Despite low levels of dimorphism in spider monkeys, high fission-fusion dynamics may lead to different activity budgets for males and females, which in turn favors segregation to meet different reproductive agendas. Males and females differ significantly in time spent traveling, feeding and socializing. Spider monkeys also prefer to associate with same-sex partners. Since males and females do not differ in habitat use, segregation in spider monkeys is best explained by sex differences in activity budgets and social preferences

Sex differences in the acoustic structure of terrestrial alarm calls in vervet monkeys (Chlorocebus pygerythrus)

© 2024 The Authors. Published by Wiley. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.1002/ajp.23674The alarm calls of vervet monkeys (Chlorocebus pygerythrus) have been the subject of considerable focus by researchers, owing primarily to the purported referential qualities of different alarm call types. With this focus on reference, acoustic variation among calls elicited by the same range of predators has typically been overlooked. Specifically, at least one type of alarm call—the terrestrial alarm—was described over 50 years ago as being acoustically distinct between males and females—a description that has largely eluded more systematic scrutiny. Here, we provide a quantitative acoustic analysis and comparison of terrestrial alarm calls produced by adult male and female vervet monkeys. We use a random forest model to determine which acoustic variables best distinguish between the calls of males and females, and use an unsupervised clustering technique to objectively determine whether alarms produced by each sex fall into discrete types. We found that the calls of males and females differed most in frequency-based parameters, with male alarms containing more energy at lower frequencies relative to females. Calls produced by males were also of longer duration, and consisted of longer individual call elements relative to female calls. While calls generally fell into clusters associated with either male or female alarms, we found that some fell into atypical clusters given the caller's sex, and that the clusters themselves showed evidence of intergradation. We discuss these results in terms of potential differences in the function of, and motivation for, calling by males and females. We emphasize the need for a more holistic approach to the classification of vocal signals that considers contextual, functional, and structural variation.Funding for this research was provided by National Research Foundation (South Africa) grants (S. Peter Henzi), the Natural Sciences and Engineering Research Council of Canada (Colin Dubreuil, Louise Barrett, Mary S. M, Pavelka, Peter Henzi), the Killam Trust (Colin Dubreuil) and the Faculty of Graduate Studies at the University of Calgary.Published versio

Traditions in spider monkeys are biased towards the social domain

Cross-site comparison studies of behavioral variation can provide evidence for traditions in wild species once ecological and genetic factors are excluded as causes for cross-site differences. These studies ensure behavior variants are considered within the context of a species' ecology and evolutionary adaptations. We examined wide-scale geographic variation in the behavior of spider monkeys (Ateles geoffroyi) across five long-term field sites in Central America using a well established ethnographic cross-site survey method. Spider monkeys possess a relatively rare social system with a high degree of fission-fusion dynamics, also typical of chimpanzees (Pan troglodytes) and humans (Homo sapiens). From the initial 62 behaviors surveyed 65% failed to meet the necessary criteria for traditions. The remaining 22 behaviors showed cross-site variation in occurrence ranging from absent through to customary, representing to our knowledge, the first documented cases of traditions in this taxon and only the second case of multiple traditions in a New World monkey species. Of the 22 behavioral variants recorded across all sites, on average 57% occurred in the social domain, 19% in food-related domains and 24% in other domains. This social bias contrasts with the food-related bias reported in great ape cross-site comparison studies and has implications for the evolution of human culture. No pattern of geographical radiation was found in relation to distance across sites. Our findings promote A. geoffroyi as a model species to investigate traditions with field and captive based experiments and emphasize the importance of the social domain for the study of animal traditions.Research at Barro Colorado Island was supported by grants from the National Science Foundation (SBR-9711161), the Leakey Foundation, the Department of Anthropology, University of California, Berkeley (www.berkeley.edu) and a Short-term Fellowship from the Smithsonian Tropical Research Institute (www.stri.org). Research at Corcovado National Park's Sirena Biological Station was supported by NSF award 0233248 (with R. Sussman), the Wenner-Gren Foundation, the Leakey Foundation, the American Society of Primatologists (www.asp.org), and Washington University in St. Louis (www.wustl.edu). Funds for Sirena's field lab facility were provided to L. E. Gilbert (Univ. of Texas at Austin) by NSF BSR 8315399 and a matching WWF grant, and funds for updating Sirena's trail system and installation of spatial reference system were provided by the Mellon Foundation through the Institute of Latin American Studies at UT Austin. Research at Santa Rosa and Punta Laguna was supported by The British Academy (www.britac.ac.uk), the Wenner-Gren Foundation (www.wennergren.org), the Leakey Foundation (www.leakeyfoundation.org) and the North of England Zoological Society (www.chesterzoo.org). CJS was supported by a Gladstone bursary from the University of Chester (www.chester.ac.uk) and by the Santander University Scheme (www.santander.co.uk). Research at Runaway Creek was supported by the Natural Sciences and Engineering Research Council of Canada. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Factors influencing terrestriality in primates of the Americas and Madagascar

Among mammals, the order Primates is exceptional in having a high taxonomic richness in which the taxa are arboreal, semiterrestrial, or terrestrial. Although habitual terrestriality is pervasive among the apes and African and Asian monkeys (catarrhines), it is largely absent among monkeys of the Americas (platyrrhines), as well as galagos, lemurs, and lorises (strepsirrhines), which are mostly arboreal. Numerous ecological drivers and species-specific factors are suggested to set the conditions for an evolutionary shift from arboreality to terrestriality, and current environmental conditions may provide analogous scenarios to those transitional periods. Therefore, we investigated predominantly arboreal, diurnal primate genera from the Americas and Madagascar that lack fully terrestrial taxa, to determine whether ecological drivers (habitat canopy cover, predation risk, maximum temperature, precipitation, primate species richness, human population density, and distance to roads) or species-specific traits (bodymass, group size, and degree of frugivory) associate with increased terrestriality. We collated 150,961 observation hours across 2,227 months from 47 species at 20 sites in Madagascar and 48 sites in the Americas. Multiple factors were associated with ground use in these otherwise arboreal species, including increased temperature, a decrease in canopy cover, a dietary shift away from frugivory, and larger group size. These factors mostly explain intraspecific differences in terrestriality. As humanity modifies habitats and causes climate change, our results suggest that species already inhabiting hot, sparsely canopied sites, and exhibiting more generalized diets, are more likely to shift toward greater ground use

Factors influencing terrestriality in primates of the Americas and Madagascar

Among mammals, the order Primates is exceptional in having a high taxonomic richness in which the taxa are arboreal, semiterrestrial, or terrestrial. Although habitual terrestriality is pervasive among the apes and African and Asian monkeys (catarrhines), it is largely absent among monkeys of the Americas (platyrrhines), as well as galagos, lemurs, and lorises (strepsirrhines), which are mostly arboreal. Numerous ecological drivers and species-specific factors are suggested to set the conditions for an evolutionary shift from arboreality to terrestriality, and current environmental conditions may provide analogous scenarios to those transitional periods. Therefore, we investigated predominantly arboreal, diurnal primate genera from the Americas and Madagascar that lack fully terrestrial taxa, to determine whether ecological drivers (habitat canopy cover, predation risk, maximum temperature, precipitation, primate species richness, human population density, and distance to roads) or species-specific traits (body mass, group size, and degree of frugivory) associate with increased terrestriality. We collated 150,961 observation hours across 2,227 months from 47 species at 20 sites in Madagascar and 48 sites in the Americas. Multiple factors were associated with ground use in these otherwise arboreal species, including increased temperature, a decrease in canopy cover, a dietary shift away from frugivory, and larger group size. These factors mostly explain intraspecific differences in terrestriality. As humanity modifies habitats and causes climate change, our results suggest that species already inhabiting hot, sparsely canopied sites, and exhibiting more generalized diets, are more likely to shift toward greater ground use

Lost in Transmission: Contextual Variation in Chimpanzee Pant Hoots and its Implications for Referential Communication in Primates

Pant hoots are the species-typical 'loud' call used by chimpanzees to communicate over long distances. Some previous studies have explored the possibility that there are acoustically distinct subtypes of pant hoots that communicate to distant listeners different information abou the caller's behaviour or ecological and social circumstances. As listerners are presumably able to elicit information about the caller's circumstance through the acoustic propoerties of the received call, chimpanzee pant hoots have variously been labeled "referential" in quality because theya ppear to share some of the symbolic properties of human language. However, results of previous studies to date have been either conflicting or inconclusive in establishing the existence of referential vocalizations in chimpanzees, and many of the interpreations of the functional similarities between chimpanzee calls and langugage have been based on preconceptions about chimpanzee cognition. These preconceptions are rooted largeley in phylogenetic assumptions; that is, because chimpanzees are closely reatled to humans there is a tendency to evaluate their cognitive abilities by the extent to which humans possess those abiltities. This talk will present data from an extensive acoustic analysis of chimpanzee pant hoots from the Budongo Forest, Uganda that I undertook to help resolve some of the issues raised above. I will offer an interpreation of the data that is consistent with an ecological, rather than phylogenetic approachy to explaining the functional significance of pant hoots. I will also discuss the relevance of this work to my current research program that is being established with New World primates

The meaning, structure and function of chimpanzee pant hoots from the Budongo forest, Uganda

Bibliography: p. 161-173Pant hoots are the species-typical loud calls produced by chimpanzees to communicate to conspecifics over long-distances. Previous studies have attempted to determine the degree to which pant hoots function as referential signals that communicate information specific to behavioural, social and ecological contexts but have produced mixed results. Uhlenbroek (1996, unpublished PhD thesis) identified three acoustically and functionally distinct sub-classes in pant hoots produced by chimpanzees from the Gombe Stream Reserve, Tanzania. Uhlenbroek labelled these variants "roar," "slow roar" and "wail" pant hoots and proposed they serve a referential function by being used in specific contexts. In this study, pant hoots were analyzed to determine whether similar functionally distinct vocal classes could be discerned in the Sonso chimpanzees of the Budongo Forest, Uganda. Using cluster and discriminant function analyses, three pant hoot types were identified quantitatively and a fourth type described qualitatively. Three of these pant hoot types exhibited varying degrees of production context specificity. However, contrary to Uhlenbroek, a strictly referential function for pant hoots is not proposed. Rather, I suggest that the structural characteristics of pant hoots are constrained by environmental, physiological and phylogenetic factors, and that the acoustic design of different pant hoot types conform to predictions concerning both motivational effect and propagation maximization in specific "layers" of the acoustic habitat. In addition, I propose the hypothesis that other acoustic cues, such as the presence of buttress drumming, the number of animals calling, the rate of calling per episode and the location of the caller relative to the ground, accompany many calls and are used by receivers to gauge the context and relevance of the call in determining a future course of action. In this manner, pant hoots might function referentially in a "weak" sense in that the interplay between the type of pant hoot produced and the suite of accompanying cues provide information concerning the context and "meaning" of the call

The Short-Term Effects of Hurricane Richard on Diet, Behaviour, and Sub-grouping Patterns of Spider Monkeys (Ateles geoffroyi) at Runaway Creek Nature Reserve, Belize

Two presentations were made concerning the behaviour and ecology of spider monkeys at our research site at Runaway Creek Nature Reserve, Belize. The first looked at patterns of aggression, and in particular female-directed aggression in spider monkeys (directed from males and other females). The second paper addressed the effects of a hurricane (Richard) on the study population. Spider monkeys are ripe fruit specialists and, as a result, are considered extremely vulnerable to habitat disturbance that disrupts the production of their food supply. Our expectation was that the hurricane would have devastating impacts on the monkeys in the short term. However, we were able to show that spiders may use flexible dietary and social strategies by relying on other fall-back foods like leaves, and by adjusting group size to mitigate feeding competition. Our results suggest that spider monkeys may be more resilient to habitat disturbance than previously thought, at least in the short term.“The Short-Term Effects of Hurricane Richard on Diet, Behaviour, and Sub-grouping Patterns of Spider Monkeys (Ateles geoffroyi) at Runaway Creek Nature Reserve, Belize” Studying the effects of natural disturbances such as hurricanes on primate populations provides valuable insight into species adaptability and their resiliency to major climatic events. We compared activity, diet, and sub-grouping patterns in a community of spider monkeys three months before and after a category 2 hurricane hit central Belize in October, 2010. Due to extensive damage to fruiting trees, we predicted that the monkeys would alter their diet to include more leaves, and that they would forage in smaller subgroups to reduce feeding competition. We also predicted that the monkeys would spend more time travelling in search of scattered resources post-hurricane, and allocate less time to social activities. Paired-sample t-tests determined that consumption of ripe fruit did decrease post-hurricane (P<0.001), while consumption of leaves, unripe fruit and flowers significantly increased relative to pre-hurricane levels. Average subgroup size decreased post-hurricane (P<.001), and sub-groups were more stable, as indicated by a decrease in the hourly rate of subgroup fissions/fusions. Contrary to our predictions, the monkeys spent significantly more time feeding (P=.001) and engaging in social activities (P=.023) post-hurricane, while the amount of time spent traveling and resting did not change. Our study suggests that dietary and grouping flexibility are critical to mitigating the immediate after-effects of major habitat disturbances, and that fission-fusion species such as spider monkeys may exhibit more short-term resiliency to such disturbances

Patterns of aggression in spider monkeys (Ateles geoffroyii yucatanensis) at Runway Creek Nature Reserve, Belize

Two presentations were made concerning the behaviour and ecology of spider monkeys at our research site at Runaway Creek Nature Reserve, Belize. The first looked at patterns of aggression, and in particular female-directed aggression in spider monkeys (directed from males and other females). The second paper addressed the effects of a hurricane (Richard) on the study population. Spider monkeys are ripe fruit specialists and, as a result, are considered extremely vulnerable to habitat disturbance that disrupts the production of their food supply. Our expectation was that the hurricane would have devastating impacts on the monkeys in the short term. However, we were able to show that spiders may use flexible dietary and social strategies by relying on other fall-back foods like leaves, and by adjusting group size to mitigate feeding competition. Our results suggest that spider monkeys may be more resilient to habitat disturbance than previously thought, at least in the short term.“Patterns of aggression in spider monkeys (Ateles geoffroyii yucatanensis) at Runway Creek Nature Reserve, Belize” K. Hartwell¹, H. Notman1, 2, & M.S.M. Pavelka¹ ¹University of Calgary, Calgary, Alberta, Canada ²Athabasca University, Alberta, Canada Presenter’s Email: [email protected] A number of studies looking at aggression in Ateles describe high rates of both male aggression directed at females (female-directed aggression by males, or M-FDA), as well as female aggression toward other females (or F-FDA). M-FDA may be an expression of feeding competition, direct sexual coercion, or indirect sexual coercion, and F-FDA may function to limit scramble competition. We collected detailed data on all observed incidences of aggression (N=193) in two spider monkey communities between January 2008 and August 2011. Of these, 154 were instances of M-FDA, and 29 incidents were F-FDA. Oneway ANOVA shows that adult and subadult males are significantly more likely to initiate aggression, and that subadult females are the most common targets. In instances of F-FDA, subadult females were the targets in 53% of the cases. Nonparametric tests show that contexts of aggression differed between M-FDA and F-FDA; M-FDA occurred most often during subgroup fusions (males joining subgroups containing females who were not feeding) and during feeding (37% and 31% respectively, N = 154); in contrast, F-FDA aggression rarely occurred during fusions but was more likely during feeding (14% and 41% respectively, N=29). Our results support the hypothesis that M-FDA is a form of indirect sexual coercion, and as a result may encourage sexual segregation as females try to avoid potentially aggressive males

Seasonal Variation in Sexual Segregation in spider Monkeys (Ateles GeoffroyI Yucatanensis) at Runaway Creek Nature Preserve Belize

I attended the annual meeting of the American Society of Primatologists in Austen, Texas during September 15-20. This meeting brings together society members, many of whom (despite the regional focus implicated in the society’s name) are internationally renowned in the discipline. I presented a paper in a symposium entitled “Ecology of Behaviour” on research that I and my current PhD student are working on – the mechanisms for, and variation in sexual segregation in spider monkeys. The data are derived from our on-going primate research site in Belize. The paper was well-received as this phenomenon has not been formally analyzed in this species. The originality of our approach involved the use of an index that has been applied to a similar phenomenon in ungulates, but never before in primates. We did receive feedback concerning other mechanisms to explore (as hypotheses to be tested) regarding the function of sexual segregation, and this is something Kayla Hartwell, my PhD student and co-author on the paper, will incorporate into her thesis project.Sexual segregation, the separation of males and females socially or by habitat, has been recognized as a dimension of the socio-ecology of many vertebrates, but has not been quantified or systematically examined in primates. We investigated temporal patterns of sexual segregation in a population of spider monkeys in Belize. Using data collected over a 23 month study, we applied the Sexual Segregation and Aggregation Statistic to test three hypotheses: i) the sexes segregate, ii) the sexes aggregate, or iii) the sexes associated at random. Our analysis revealed that spider monkeys live in primarily sex-segregated societies, but that patterns of segregation varied within and between years: males and females segregate most of the year, except when food availability is lowest. Males and females had significantly different activity budgets; males spent more time travelling, and less time resting and feeding, than females. However, same-sex groups were less synchronous in their behavioural activities than were mixed groups. Males had a higher proportion of ripe fruit in their diets than females did, who ate more leaves and unripe fruit. We propose that sexual segregation in spider monkeys is primarily a form of social segregation that results from males and females pursuing different strategies for optimizing sex-specific energy requirements and reproductive demands. We suggest that the fission-fusion social patterning typical of spider monkeys in which males and females often form same-sexed subgroups emerges from social segregation. Supported by NSERC and Athabasca University research fund