Dissertations / Theses on the topic 'Ateles geoffroyi'

Animals living in groups are frequently exposed to conflicts of interest which can escalate into aggression. Aggressive interactions may be a means to resolve incompatibility among objectives. Nevertheless, aggression may undermine the benefits of group living by disrupting the relationships between opponents. Thus, conflict management mechanisms have evolved to cope with the potential damage brought about by aggressive interactions. The aim of my thesis was to investigate the mechanisms to prevent aggressive escalation and to mitigate its negative consequences in 2 communities of wild spider monkeys (Ateles geoffroyi yucanensis). I also examined the factors, such as relationship characteristics, affecting the occurrence of these mechanisms. Spider monkeys live in communities with a high degree of fission fusion dynamics in which individuals frequently split and merge into subgroups of variable composition. The implications of this social system for conflict management were also explored. To characterise spider monkeys’ social relationships, two components were identified and labelled compatibility and risk. These components were further related to relationship characteristics, such as kinship, sex combinations, and tenure in the community. Kin had more compatible relationships than non kin, but there was no difference for risk. Male-male dyads were characterised as being significantly more compatible and riskier than either female-female dyads or male-female dyads. Furthermore, individuals with longer tenure had riskier relationships than individuals with shorter tenure. Among the post-conflict management mechanisms spider monkeys did not engage in reconciliation, redirected aggression, or bystander affiliation. However, an option afforded by their high degree of fission fusion dynamics was used in the aftermath of aggression. Fission from former aggressors was more likely to occur within one hour of the aggressive conflicts than in control periods. Furthermore, individuals sharing riskier and less compatible relationships had significantly shorter latencies to fission compared to those with less risky and more compatible relationships. These patterns suggest that fission may function to reduce the possibility of renewed aggression and cope with increased post-conflict anxiety. Indeed, anxiety levels were higher in the recipients of aggression during the first 5 post-conflict minutes compared to baseline levels. Whereas fission may be a mechanism to cope with the negative consequences of aggressive escalation, fusion of subgroups could lead to uncertainty and hostility. Indeed, aggression increased in the first five post-fusion minutes compared to baseline levels. There was also an increase in post-fusion friendly behaviours, which may function as signals of good intentions. This view was confirmed as post-fusion aggression was reduced when friendly behaviours took place. In addition, shorter latencies of post-fusion aggression and friendly behaviours were found between individuals with riskier relationships compared to those with less risky relationships. Prevention of aggressive conflicts may also be achieved by adjusting subgroup size to the availability of feeding resources thereby reducing competition. The effectiveness of this flexible adjustment was demonstrated during a period of drastic reduction in food sources caused by two consecutive hurricanes at the field site. Mean subgroup size and fusion rates were significantly reduced in the post-hurricane compared to pre-hurricane periods. Hence, my thesis adds to the study of social relationships and conflict management in non-human animals by making several contributions. I provided the first evidence of relationship components in new world monkeys. I then examined the potential of fission-fusion dynamics as a means to manage conflicts among community members. I was the first demonstrating that fission is a post-conflict mechanism. Fission from the former aggressor was especially used by individuals with riskier and less compatible relationships. Subgroup fusion increased aggressive conflicts, especially between individuals with riskier relationships, but post-fusion friendly behaviours reduced them. The effectiveness of fission-fusion dynamics in conflict management was further demonstrated by how the spider monkeys coped with the potential increase in conflict among community members due to a dramatic reduction in food supplies due to two hurricanes. Overall, spider monkeys appear to deal with conflicts using the full range of the flexible social options afforded by their social system.

Primates have traditionally been viewed as having a poorly developed sense of smell. However, in recent years, studies have shown that at least some primate species use olfaction in a number of behaviors, and that they have a high olfactory sensitivity for various chemical classes of odorants. Using a two-choice instrumental conditioning paradigm, the present study assessed olfactor ydetection thresholds of three spider monkeys (Ateles geoffroyi) for eight aliphatic alcohols and aldehydes, known as "green odors". With all odorants, the animals detected concentrations below 1 parts per million, with single individuals performing even better. The type of functional group present systematically affected olfactory detection thresholds, whereas the presence, position and configuration of a double bond did not. Compared to previously tested classes of odorants, thespider monkeys were not particularly sensitive to "green odors". Furthermore, they are lesssensitive for "green odors" compared to humans and mice. The present results suggest that neuroanatomical and genetic comparisons across species are poor predictors of olfactory sensitivity.

For many years, primates have been considered to be animals with a poorly developed sense of smell. However, in recent years several studies have shown that at least some primate species have a high olfactory sensitivity for a variety of odorants. The present study used a two-choice instrumental conditioning paradigm to test the olfactory sensitivity for six aromatic aldehydes in four spider monkeys (Ateles geoffroyi). With helional, cyclamal,canthoxal and lilial all animals discriminated concentrations below 1 ppm from the odorless solvent, with single individuals even scoring better. With 3-phenyl-propionic aldehyde all animals detected concentrations below 2 ppb, and with bourgeonal even below 0.3 ppb. The detection thresholds of the odorants changed systematically with molecular structure. Addition of a dioxo or methoxy group to the benzene ring led to an increase in threshold values,while the absence of a methyl group close to the aldehyde moiety was linked to a low threshold value for the odorant. The study shows that spider monkeys have a well developed olfactory sensitivity for aromatic aldehydes.

The first study on Ateles geoffroyi in Honduras, this research focused on the population of spider monkeys in Parque Nacional Pico Bonito, Atlántida, Honduras. Subgroup size of spider monkeys in Parque Nacional Pico Bonito ranged from 1-23 (n=55) individuals, with a mean subgroup size of 6.93 ± 4.53 individuals, which was larger than nearly all subgroup sizes reported in Central and South America. Mean subgroup composition consisted of 1.65 ± 1.16 adult males, 2.67 ± 1.69 adult females and 1.75 ± 1.92 juveniles. Sex ratio of adult males to adult females was 1:1.62, which was consistent with most Central and South American Ateles studies in the literature.¶ Of a possible 23 identified food tree species from 15 families, and 7 unidentified tree and vine species, spider monkeys were confirmed to consume fruits, leaves and/or seeds from 8 identified tree species, 1 unidentified tree species, and 1 unidentified vine species. Several of the confirmed genera consumed by Ateles in Parque Nacional Pico Bonito were consistent with other studies conducted in Central and South America, including Dialium, Ficus, and Coccoloba.¶ Combining pelage analysis and discriminant analysis of cranial and dental measurements from 140 skins and 253 adult crania, the taxonomy of the Central American Ateles geoffroyi was revised to recognize the taxa Ateles geoffroyi yucatanensis, A. g. vellerosus, A. g. pan, A. g. geoffroyi, A. g. frontatus, A. g. ornatus, and A. g. grisescens, with the recognition of a potential new taxon from northern Honduras, resulting in a revised distribution of Ateles geoffroyi, based on the pelage and cranial analyses.

Cognition allows animals to acquire, process, and store sensory information from the environment and use it to adapt to their surroundings. A battery of behavioral tests was used to assess the cognitive abilities of black-handed spider monkeys (Ateles geoffroyi). Black and white cups were used to assess (1) object permanence by showing the animals under which cup the reward was placed, (2) associative learning by concealing where the reward was placed, and (3) long-term memory by repeating the second task after a 4-month break; petri dishes with varying amounts of food were used to assess (4) relative quantity discrimination; and boxes fitted with dotted cards were used to assess discrete number discrimination with (5) equallysized dots and (6) various-sized dots. For each task, one session comprised 10 trials (i.e. responses). All nine animals succeeded in all tests and, as a group, reached the learning criterion of 70% correct responses on session two in the object permanence and associative learning tasks; on session eleven in the quantity discrimination task; on session sixteen in the numerosity task with equally-sized dots; on session three in the numerosity task with various-sized dots; and averaged 84.4% correct responses in the long-term memory task. Their prompt high score in the numerosity task with various-sized dots suggests that the animals acknowledged the task for its numerical properties as opposed to the size or pattern of the dots. These cognitive abilities are thought to shape the necessary behaviors for the ecological and social needs of the species.

A 12-month study of the ranging behaviour of 11 spider monkeys (Ateles geoffroyi yucatanensis) was undertaken at the Otochma' ax Yetel Kooh nature reserve in the state of Yucatan, Mexico. The aims were: 1) to evaluate the relationship between ranging patterns of the monkeys and ecological features i.e. climate and food distribution, 2) to assess the efficiency of ranging patterns, and 3) to test the hypothesis that spider monkeys navigate between important sources through spatial memory of key locations. A focal animal was followed daily for as long as possible and details of its ranging patterns recorded by entering positional fixes with a GPS receiver. Behavioural states were included in the observations to link them with the geographical information recorded simultaneously. The results revealed that the ranging patterns of spider monkeys at the study site were determined by the availability of key species of fruit in the area. Ranging was efficient, as evidenced by the fact that in most instances - particularly in the dry season when food was scarce - (1) spider monkeys moved in straight lines to distant food sources, (2) were able to orient their movement toward a food source at distances that could not have been in sight from the point where directed movement originated, and (3) the successive organisation of these linear segments was consistently forward, suggesting an ability to plan ahead of the next food source visited. I present these results as evidence of the use of spatial memory to move efficiently between important sources in their environment, and I argue in favour of higher-level spatial abilities in this species of New World monkeys.

The aim of this thesis was to provide a better understanding of the needs of spider monkeys (genus: Ateles) kept in zoological parks in order to provide an appropriate environment, which enhances the physical and emotional wellbeing of the individuals. This series of studies adopted primarily a physiological approach that entailed measuring cortisol in urine samples collected over a seven year period to assess the impact of a variety of social and environmental conditions. My studies also involved behavioural observations and a questionnaire study to collect information from other zoological parks that maintain groups of spider monkeys. In order to address the aims of my research I first validated an enzyme immunoassay for urinary cortisol which allowed for the activity of the HPA axis to be measured to assess the physiological stress responses in spider monkeys. The first study assessed the impact of visitors on spider monkeys by comparing levels of urinary cortisol collected with visitor numbers and I found an increase in visitor numbers was associated with an increase in cortisol. This was the first time the physiological impact of visitors was investigated and supports behavioural researcher that visitors adversely impact on primates in zoos. The second study I carried out involved a questionnaires to investigate frequency, direction and intensity of aggression in zoo-housed spider monkeys in 55 other zoos around the world. The pattern of aggressions reported indicated severe and lethal aggression was relatively frequent among captive spider monkeys. Adult males were the most frequent actors of aggression and sub adult males were the most frequent targets, contradicting reports from wild spider monkeys. This aggression could be a condition of the management of spider monkeys in the zoos whereby males and normally transferred between zoos contradicting reports from the wild spider monkeys in which females would emigrate on reaching maturity. Next I investigated aggression, reproductive and separation stressors in the spider monkeys housed at Chester Zoo over a seven year period and measured their effects via changes in urinary cortisol prior to, at and following each event. Aggression had the largest effect, with targets and bystanders having the highest levels of cortisol on the day of aggression for severe and lethal aggression, respectively. When examining the reproductive events, cortisol levels were significantly elevated in the mother the week prior to and the day or birth, but were highest for bystander females on the day of birth. In the case of separations, cortisol was elevated when an individual was separated for longer than 24 hours for separations and less than 24 hours for reintroductions. Finally I investigated the replacement of the breeding male in the spider monkeys at Chester Zoo. Although a significant behavioural effect was identified in the adult females, there was little evidence of an increase in urinary cortisol among them. In addition, there were no instances of aggression between the adult males and the juvenile male in the group. Overall conclusions from this study indicate that the group of spider monkeys did demonstrate a varying stress response to a variety of social and environmental stressors associated with elevated cortisol levels and behavioural changes. However, there was no evidence of long term chronic stressors which are normally associated with poor welfare. This indicated that the environmental provided for this particular group of zoo-housed spider monkeys generally allowed for the individuals within the group to cope and adapt. In light these findings the study also makes a number of recommendations regarding the enclosure design, relocated of individuals and the gradual introduction of spider monkeys in zoos. The findings of this study are important as it contributes to our understanding of the physiological responses to stressors in a zoo environment and therefore has implications for animal management. It also identifies potential species specific requirements for the spider monkey that should be considered.

Studies on taste perception in nonhuman primates contribute to the understanding of the evolution of the sense of taste. To assess the responsiveness of four adult spider monkeys (Ateles geoffroyi) to a set of substances perceived as sweet by humans, two-bottle preference tests were performed to determine taste preference thresholds, and taste-induced facial responses were analyzed. The spider monkeys displayed a significant preference for concentrations as low as 0.2-1 mM acesulfame K, 0.002-0.5 mM alitame, 10-20 mM isomalt, 0.002-0.5 mM sodium saccharin, 2-20 mM galactose and 20-50 mM sorbitol over water. The spider monkeys were generally unable to perceive aspartame and, based on their facial responses, probably do not perceive it as sweet. Thaumatin and monellin were not detected, and most likely neither was the sweetness of sodium cyclamate. Sodium saccharine and sodium cyclamate were rejected at high concentrations by at least one monkey, which is congruent with the perception of a bitter side taste as reported in humans. A significant correlation was found between the ranking order of sweetening potency for the different substances of spider monkeys and humans, but not between spider monkeys and chimpanzees. The results suggest that spider monkeys may be generally more sensitive than chimpanzees and at least as sensitive as humans to the tested substances, supporting the notion that high sensitivity to sweet taste may be associated with a frugivorous dietary specialization. The lack of responsiveness to some of the substances supports the notion of a dichotomy in sweet-taste perception between platyrrhine and catarrhine primates.

This project arose because of the desire by the resident Ateles research observers, at Santa Rosa, to attempt to ascertain a function for what they deemed ‘uncharacteristic’ behaviours. The following were important considerations meriting further investigation. • Phoradendron (mistletoe) consumption by Ateles spp. appeared to be present only at Santa Rosa; • Mistletoe selection was considered deliberate, as mature host leaf (which was available) was not selected; • More than one mistletoe was available in the normal home range of the monkey, but selection was dominated by one mistletoe/host combination; • Consumption was of relatively small volumes; • There was an apparent seasonality to the use of mistletoe; • Consumption of mature, mistletoe leaf occurred at times when there was no shortage of suitable fruit; • Limitations of the Ateles spp. digestive system made exploitation of mature leaf potentially problematic; • The monkeys were also seen consuming geophageous material; on occasion, this closely followed mistletoe consumption; • There were no published reports of Ateles spp. geophagy in Central America and/or tropical dry forest habitat. The aim of the subsequent investigation was to determine if there was any beneficial function that could be attributed to the materials and so provide a link to a self-mediation hypothesis for mistletoe and/or geophagy or to relate the determined geophagy properties to the other published functional hypotheses for geophagy. The novel aspect of this project was the development of a specific ‘gastric model’ reflecting the differences between Ateles and human digestive systems. This modified model was used to investigate geophagic and Phoradendron samples. It was hoped that this approach would lead to the identification or constituents in the samples, which may have physiological significance. Samples of the two species of mistletoe identified were collected from three Phoradendron/host tree combinations. Samples were extracted using the simulated gastric conditions and the extracts analysed. Analytical ‘fingerprints’ of the gastric extracts of the two species were obtained together with the antimicrobial activities of the extracts. Species variation in Phoradendron constituents and antimicrobial activity was detected. The principal difference between the eaten and non-eaten Phoradendron species was identified using HPLC and LC-MS, as chlorogenic acid. Chlorogenic acid has antibacterial and antioxidant properties, stimulates the immune system and has activities related to regulation of blood sugar levels. Phoradendron consumption wass during the wet season, which may be a period of increased bacterial and parasite infection. It also coincides with a change in dietary fruits. The geophagic samples were taken from sites previously used by Ateles, together with ‘control’ sites found in the home range of the study group. Analysis of the physical properties and characteristics was undertaken to attempt to identify the mineral content material. Further analyses then investigated the behaviour of the material in relation to the commonly accepted hypotheses for geophagy. Where possible these were investigated using the simulated gastric conditions. The physical characteristics of the samples did not resemble the previously published reports for geophagic material used by humans or non-human primates. The results failed to detect the presence of montmorillonite and only a suggestion of the presence of kaolinite. The results do not suggest that it functions as an antacid, an anti-diarrhoeal or mineral supplement. An increase in antibacterial activity was seen when geophagic material and Phoradendron samples were incubated together. A putative hypothesis for the mechanism of Fe limitation was suggested by the physical properties of the geophagic material and the Fe chelating potential of the chemical constituents of the Phoradendron leaf.

The problems of what primates communicate with their vocalizations and to what extent they refer to events in the external environment are raised in numerous studies of primate vocal communication. To investigate these issues, I concentrate on the calls of two primate species with a similar fission-fusion social organization. I report here the results of a one year field study on the Central American spider monkey (Ateles geoffroyi frontatus) and of a captive study on the chimpanzee (Pan troglodytes). I collected observational data and conducted playback experiments on two types of calls of the spider monkey, whinnies and alarm barks. Spider monkeys use two functionally distinct whinnies, a feeding whinny and a locational whinny. Detailed acoustic analyses of whinnies given in different contexts showed that in three females an acoustic feature-number of arches in the fundamental frequency of the call- could be used to differentiate between them. Although the whinnies of different monkeys within the same community exhibit enough acoustical differences for individual vocal recognition to take place, spider monkeys did not discriminate familiar individuals' whinnies from those of strangers from another community. In predator contexts spider monkeys use barks to attract other conspecifics to a site. However, my data do not support the existence of two types of alarm barks for aerial versus terrestrial predators. I conducted two different types of experiments on the calling behaviour of captive chimpanzees in response to food-finding. I examined whether the quantity and divisibility of food, or the presence of an audience, influence calling behaviour. Chimpanzees' food- associated calls, i.e. rough grunts, functioned to indicate food availability, and they were produced or suppressed depending on how shareable the food was and whether or not other individuals were nearly. Several spider monkeys' and chimpanzees' calls have the ability to function referentially, but cannot be considered devoid of a motivational content.

The present study assessed the taste responsiveness of four female spider monkeys (Ateles geoffroyi) to the 20 proteinogenic amino acids and determined taste preference thresholds for Glycine and L-Proline. To this end a two-bottle preference test of brief duration (1min) was employed. When presented at a concentration of 200 mM, the spider monkeys significantly preferred three proteinogenic amino acids (Glycine, L-Proline and L-Alanine) over fresh water whereas four other amino acids were significantly rejected (L-Tyrosine, L-Valine, L-Cysteine and L-Isoleucine). At a concentration of 100 mM, seven proteinogenic amino acids were significantly preferred (Glycine, L-Proline, L-Alanine, L-Glutamic acid, L-Aspartic acid, L-Serine and L-Lysine) whereas one was significantly rejected (L-Tryptophan). A comparison between the taste qualities of the amino acids as described by humans and taste preference/rejection responses observed with the spider monkeys suggests a fairly high degree of agreement in perception of these taste substances between the two species. When given the choice between fresh water and defined concentrations of two amino acids that taste sweet to humans the spider monkeys were found to significantly discriminate concentrations as low as 10-50 mM of Glycine and 10-40 mM of L-Proline from the solvent. This suggests that spider monkeys are similar in their taste sensitivity for Glycine and L-Proline compared to humans and slightly more sensitive compared to mice.

There is little knowledge about olfactory learning in primates, even though primates are known to use olfaction in several behaviors including food selection and territorial defense. Therefore I assessed the olfactory learning and memory performance in five adult spider monkeys (Ateles geoffroyi) using a food-rewarded two-choice olfactory discrimination paradigm. The spider monkeys acquired the initial odor discrimination in 530-1102 trials and in a series of intramodal transfer tasks they needed 30-510 trials to reach the learning criterion. There was a significant negative correlation between the number of trials needed to reach the learning criterion and the number of transfer tasks completed. Thus, as a group, the animals displayed olfactory learning set formation. The number of trials that the spider monkeys needed in initial olfactory learning was comparable to that of other primate species tested previously but higher compared to that of other mammals such as dogs and rats. The learning speed of the spider monkeys in intramodal transfer tasks was similar to that of other mammals tested, suggesting that primates are less prepared to use olfactory cues in the initial solving of a problem but that once they learn the concept, their learning speed with novel odor discrimination problems is not generally slower than that of non-primate mammals. All spider monkeys tested reached the learning criterion in the memory tasks straight on the first testing day, that is: within 30 trials, suggesting similar long-term odor memory capabilities in spider monkeys and other mammals such as dogs, mice and rats.

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O estudo das diferenças sexuais secundárias em macacos-aranha (gênero Ateles É. Geoffroy, 1806) tem apresentado resultados controversos, principalmente em relação ao peso do corpo. Os resultados vão desde positivamente dimórficos, onde os machos são maiores que as fêmeas, até negativamente dimórficos, com fêmeas maiores que os machos. No entanto, sabe-se que o grupo apresenta o menor grau de dimorfismo entre os Atelídeos. Considerando que diferenças sexuais em relação à massa do corpo influenciam diretamente nas medidas cranianas do indivíduo, foram realizadas comparações de 25 medidas cranianas e três medidas corpóreas de três espécies de primatas do gênero Ateles com distribuição amazônica, A. paniscus, A. marginatus e A. chamek. Foram utilizadas amostras de exemplares adultos depositados em três museus brasileiros. Não havia amostras suficientes da espécie A. belzebuth para a realização da análise. Além das análises morfométricas, foi realizada uma comparação etária para o tamanho da faixa de pêlos brancos da face dos exemplares de A. marginatus. As medidas cranianas foram comparadas entre os sexos através de análises multivariadas, (análise de componentes principais-ACP e análise discriminante-AD), enquanto que as medidas do corpo e da mancha frontal foram comparadas através da ANOVA. A espécie A. marginatus não apresentou diferenças sexuais no padrão de distribuição dos pêlos brancos da face, porém o mesmo parece sofrer influência da idade. Para as medidas relacionadas ao corpo, somente as espécies A. paniscus e A. marginatus apresentaram amostras suficientes para a realização das análises estatísticas. Para ambas espécies não foram observadas diferenças entre os sexos, salvo para a do comprimento da cauda de A. paniscus, que se apresentou como negativamente dimórfica. No entanto, esse resultado pode ser reflexo de erros na mensuração dos exemplares no momento da coleta. Para as medidas cranianas e mandibulares, todas as espécies apresentaram poucas variáveis dimórficas, mas em relação ao tamanho do dente canino, as diferenças entre machos e fêmeas foram altamente significativas. Outras medidas que se apresentaram como dimórficas foram aquelas relacionadas ao aparato mastigatório. Considerando que essas estruturas participam diretamente das relações de competição e hierarquia, o baixo grau de dimorfismo sexual associado ao gênero Ateles pode ser resultado do seu sistema social do tipo fissão-fusão. Uma comparação foi realizada com dados de literatura dos chimpanzés que possuem o mesmo sistema de organização social, porém apresentam-se mais dimórficos. Foi verificado que diferenças no modo de forrageamento, organização e utilização do habitat pelas fêmeas podem determinar um crescimento diferenciado em relação aos machos e, consequentemente, ter influência no grau de dimorfismo apresentado por essas espécies. Apesar de ter sido considerado, no presente estudo, como um grupo monomórfico, as diferenças sexuais em Ateles parecem ser mais evidentes na idade subadulta. Portanto, faz-se necessário um estudo ontogenético que realize um melhor refinamento da classe adulta a fim de determinar, aproximadamente, em que período do ciclo de vida desses primatas ocorre essa diferenciação, e quais fatores ecológicos ou comportamentais podem ser associados a essa característica.
The study of the secondary sexual differences in spider monkeys (Ateles É. Geoffroy gender, 1806) has shown controversial results, mainly concerning the body weight. Results range from positively dimorphic, where males are larger than females, to negatively dimorphic, with females larger than males. However, it is known that the group presents the lowest degree of dimorphism amongst the Atelid species. Considering that sexual differences related to body mass directly influence on the skull measurements of the individual, comparisons have been made from 25 skull measurements and 03 body measurements from three species of primates of the Ateles gender with Amazon distribution, A. paniscus, A. marginatus and A. chamek. Samples of adults from three Brazilian museums were used. There were not samples enough from species A. belzebuth for the performance of the analysis. Besides the morphometric analyses, it was performed an age comparison as for the size of the white hair stripe on the face of the A. marginatus. Skull measurements have been compared between sexes through multi-varied analyses, (analysis of the main-ACP components and discriminator-AD analysis), whilst the measurements of the body and the frontal spot have been compared through the ANOVA. The A. marginatus species did not present sexual differences in the pattern of distributions of the white hair on the face, but it seems to be influenced by aging. For the measurements related to the body, only the species A. paniscus and A. marginatus presented samples enough to the performance of statistical analyses. For both species it was not observed differences between sexes, except as for the length of the tail of A. paniscus, which was negatively dimorphic. However, such a result may be the reflex of mistakes at the measurement of the individuals at the moment of data collecting. To the skull and jaw measurements, all species presented few dimorphic variables, but, as for the size of the canine tooth, the differences between males and females were highly significant. Other measurements which were recognized as dimorphic were those ones related to the masticator apparatus. Considering that these structures participate directly on the relationships of competition and hierarchy, the low degree of sexual dimorphism associated to the Ateles gender may be the result of its social system of the fission-fusion type. A comparison has been performed with literature data about chimpanzees that pursue the same system of social organization, but present more dimorphism. It was verified that differences of the foraging, organization and use of the habitat by the females may determine a differentiated growth of the males and, consequently, have influence in the degree of dimorphism presented by these species. In spite of being considered, in the present study, as a monomorphic group, the sexual differences in Ateles seem to be more evident at the sub-adult age. Hence, it is necessary an ontogenetic study that shall perform a better refining for the adult class in order to determine, approximately, in what period of the life cycle of these primates such a differentiation occurs and what ecological or behavioral factors may be associated to this characteristics.

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CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
A distribuição da precipitação ao longo dos meses influencia na distribuição anual dos recursos alimentares e a forma como esses recursos se encontram em um ambiente faz com que primatas adotem diferentes estratégias para ter acesso aos mesmos. Em nosso estudo, avaliamos as variações no comportamento e dieta do macaco-aranha-da-cara-branca (Ateles marginatus) na RPPN do Cristalino. Os primatas foram acompanhados e dados comportamentais e de dieta coletados sistematicamente ao longo de nove meses, entre setembro de 2011 até maio de 2012, pelo método de varredura instantânea. A variação em relação ao orçamento de atividades, uso do espaço e dieta foi analisada para três períodos caracterizados por distintas quantidades de pluviosidade (início das chuvas, pico e transição chuva seca). No pico das chuvas os primatas aparentemente maximizaram seu consumo energético, locomovendo-se mais (43,8%) de modo a ter mais acesso aos frutos, que provavelmente estavam mais disponíveis no ambiente, ingerindo-os mais (96,5%) e descansando menos (18,5%). As classes de altura superiores (>20 a 30 metros) foram mais utilizadas nos períodos de chuva, tanto no início quanto no pico, pelo menos em parte como forma de se abrigarem das chuvas e a área de vida e os percursos diários foram maiores no início das chuvas. Houve predominância de fêmeas nos agrupamentos, com machos sendo mais registrados (36,2%) no início das chuvas, provavelmente para copular, atividade que teve a maioria de seus registros ocorrendo em um mês (dezembro) desse mesmo período. Subgrupos maiores foram registrados em períodos de maior precipitação, e subgrupos menores em épocas mais secas parecem fazer parte da estratégia para evitar a competição intraespecífica. A dieta foi majoritariamente frugívora, sendo distinta na transição da chuva para a seca, não só pela menor contribuição de frutos maduros (54,3%) como também pela contribuição de folhas novas (35,8%), quando comparado aos outros dois períodos, quando frutos maduros compuseram mais de 70% da dieta. A diversidade da dieta de frutos maduros foi concentrada em um pequeno número de espécies-chave de plantas frutíferas e os frutos costumavam ser ingeridos por inteiro, com o descarte das sementes sendo pouco comum e ocorrendo apenas para poucas espécies. As sementes ingeridas passavam intactas pelo trato digestório dos macacos-aranha e o consumo de lagartas foi limitado a um curto período de tempo, constituindo fonte alternativa de proteína. Itens alternativos como madeira em decomposição e terra de cupinzeiros em meses de baixa precipitação parecem complementar a dieta ao mesmo tempo que suprem os primatas de nutrientes tais como sódio, cálcio e fósforo, pouco presentes em frutos maduros e o consumo de Eichhornia sp., embora pouco registrado, sugere que essas plantas aquáticas tenham conteúdo nutricional importante na dieta desses primatas. A alta frugivoria dos macacos-aranha e sua capacidade de dispersar sementes intactas para longe das plantas-mãe, reforçam sua importância na regeneração das florestas e justificam sua conservação e de seus habitats. Informações referentes à ecologia comportamental e dieta desses primatas, embora básicas, são pioneiras e essenciais para compreendermos as estratégias adaptativas da espécie.
The distribution of precipitation over the months, influences on annual distribution of food resources and how these resources can be found in an environment causes primates to adopt different strategies in order to gain access to them. In our study, we evaluated the variations in behavior and diet of the white whiskered spider monkey (Ateles marginatus) at the Cristalino Private Reserve. The primates were followed and behavioral and diet data was systematically collected over nine months, between September 2011 until May 2012, through the scan sampling method. The variation concerning activity budget, use of space and diet was analyzed for three periods characterized by distinct rainfall amounts (early rains, rainfall peak and transition from rain to drought). At the peak of the rains, the primates apparently maximized its energy consumption, moving more (43.8%) so as to have more access to fruits, which were probably more available in the environment, eating more fruits (96.5%) and resting less (18.5%). Upper height classes (>20 to 30 meters) were most widely used during periods of rain, both at the beginning and in the peak, at least in part as a way to shelter from the rain and the ranging area and daily journey lengths were higher at the early rains period. There was a predominance of females in the subgroups, with males being more recorded (36.2%) at the beginning of the rainy season, probably to copulate, an activity that had most of their records occurring in one month (December) for that same period. Largest subgroups were recorded during periods of increased precipitation, and smaller sub-groups in drier times seem to be part of the strategy to avoid intraspecific competition. The diet was mostly frugivorous, being distinguished in the transition from rain to drought, not only by the lower contribution of ripe fruits (54.3%) as well as the contribution of young leaves (35.8%), when compared to the other two periods, when ripe fruits composed more than 70% of the diet. Diet diversity of ripe fruit was concentrated in a small number of key species of fruit trees and the fruits used to be swallowed whole, with the disposal of seed being unusual and occurring only for few species. Seeds ingested passed intact by the digestive tract of spider monkeys and caterpillars’ consumption was limited to a short period of time, constituting an alternative source of protein. Alternative items like decaying wood and earth from termite nests in months of low rainfall seem to complement the diet at the same time that also supply the primates’ diet with nutrients such as sodium, calcium and phosphorous, which are less present in ripe fruits, and the consumption of Eichhornia sp., although little recorded, suggests that these aquatic plants are important nutritional content in the diet of these primates. High frugivory of spider monkeys and their ability to disperse intact seeds away from the parent plants, reinforce its importance in the regeneration of forests and justify their conservation and their habitats. Information regarding the behavioral ecology and diet of these primates, though basic, are pioneering and essential to understand the adaptive strategies of the species.

The first study on Ateles geoffroyi in Honduras, this research focused on the population of spider monkeys in Parque Nacional Pico Bonito, Atlántida, Honduras. Subgroup size of spider monkeys in Parque Nacional Pico Bonito ranged from 1-23 (n=55) individuals, with a mean subgroup size of 6.93 ± 4.53 individuals, which was larger than nearly all subgroup sizes reported in Central and South America. Mean subgroup composition consisted of 1.65 ± 1.16 adult males, 2.67 ± 1.69 adult females and 1.75 ± 1.92 juveniles. Sex ratio of adult males to adult females was 1:1.62, which was consistent with most Central and South American Ateles studies in the literature.¶ Of a possible 23 identified food tree species from 15 families, and 7 unidentified tree and vine species, spider monkeys were confirmed to consume fruits, leaves and/or seeds from 8 identified tree species, 1 unidentified tree species, and 1 unidentified vine species. Several of the confirmed genera consumed by Ateles in Parque Nacional Pico Bonito were consistent with other studies conducted in Central and South America, including Dialium, Ficus, and Coccoloba.¶ Combining pelage analysis and discriminant analysis of cranial and dental measurements from 140 skins and 253 adult crania, the taxonomy of the Central American Ateles geoffroyi was revised to recognize the taxa Ateles geoffroyi yucatanensis, A. g. vellerosus, A. g. pan, A. g. geoffroyi, A. g. frontatus, A. g. ornatus, and A. g. grisescens, with the recognition of a potential new taxon from northern Honduras, resulting in a revised distribution of Ateles geoffroyi, based on the pelage and cranial analyses.

Thesis (M.S.)--University of Wisconsin--Madison, 1985.
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