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 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.

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.

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.

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.

No description available.