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Due to several factors such as ecological conditions, group size, and social organization, primates frequently spend time out of visual contact with individuals of their own group. Through the use of long‐distance vocalizations, often termed “contact calls,” primates are able to maintain contact with out‐of‐sight individuals. Contact calls have been shown to be individually distinct, and reverberation and attenuation provide information about caller distance. It is less clear, however, whether callers actively change the structure of contact calls depending on the distance to the presumed listeners. We studied this question in spider monkeys (Ateles geoffroyi), a species with complex spatial dynamics (fission‐fusion society) that produces highly frequency modulated contact calls, denominated “whinnies.” We determined the acoustic characteristics of 566 whinnies recorded from 35 free‐ranging spider monkeys that belong to a community located in Mexico, and used cluster analyses, discriminant function analyses, and generalized linear mixed models to assess if they varied in relation to the presumed distance to the listener. Whinnies could be grouped into five subtypes. Since the lowest frequency subtype was mainly produced by spider monkeys that exchanged whinnies at longer distances, and lower frequency calls propagate across longer distances, our results suggest that whinnies vary in order to enhance vocal contact between individuals separated by different distances. Our results also revealed that whinnies convey potential information about caller immediate behaviors and corroborated that these calls are individually distinct. Overall, our results suggest that whinny acoustic variation facilitates the maintenance of vocal contact between individuals living in a society with complex spatial dynamics. [ABSTRACT FROM AUTHOR]

Abstract: Background: The physiological mechanisms that allow for sleeping in a vertical position, which is primordial for arboreal primates, have not been studied yet. Methods: A non‐invasive polysomnographic study of 6 spider monkeys (Ateles geoffroyi) was conducted. The relative beta power of the motor cortex and its linear relation with muscle tone in the facial mentalis muscle and the abductor caudae medialis muscle of the tail during wakefulness and sleep stages were calculated. Results: A strong negative linear relationship (r = −.8, P = .03) was found between the relative power of the beta2 band in the left motor cortex and abductor caudae medialis muscle tone during delta sleep. Conclusions: The left motor cortex, through beta2 band activity, interacts with abductor caudae medialis muscle tonicity during delta sleep. This interaction takes part in the mechanisms that regulate the sleep postures. [ABSTRACT FROM AUTHOR]

Most primates live in habitats with some level of anthropogenic disturbance, and such disturbances have a larger impact on frugivorous primates that are more sensitive to ecological disruptions than folivores. Fecal glucocorticoid metabolites provide insight into how the external environment affects internal physiological state, and thus provide information on how anthropogenic pressures become embodied. Here, I examine how subgroup size and glucocorticoids vary with high and low fruit abundance, and how fruit abundance, subgroup size, and activity budget affect fecal glucocorticoid metabolites in female spider monkeys ( Ateles geoffroyi) living in an anthropogenically disturbed habitat. I measured these variables via behavioral, ecological, and fecal sampling for 15 months in 17 female spider monkeys at El Zota Biological Field Station. Subgroup size was significantly larger during periods of high fruit abundance, but glucocorticoids did not differ between periods of low and high fruit abundance. Monthly fruit abundance predicted subgroup sizes significantly, but did not predict fecal glucocorticoid concentrations. Increased resting time and reproductive state predicted fecal glucocorticoid concentrations significantly, but travel and foraging time had no significant effect on glucocorticoid concentrations. Individual resting time over the study period correlated negatively with glucocorticoid concentrations. These results suggest that spider monkeys cope with variation in fruit abundance by adjusting subgroup size, and that these adjustments may mitigate environmental stress in this mildly seasonal environment. The large, relatively productive forest size at this site, and the availability of anthropogenic food sources, enable this population of spider monkeys to cope with human-induced habitat disturbance. [ABSTRACT FROM AUTHOR]

Group living leads to competition for food between group members. Two types of intragroup food competition may occur: scramble competition, in which all group members use the same resource, such that feeding opportunities are equal for everyone; and contest competition, in which some group members monopolize resources through aggression and dominance. In species in which females disperse from the natal group and immigrate into other groups, immigrant females increase group size and thus possibly food competition. Under these circumstances, other females may use aggression to discourage new females from joining the group. We assessed the distribution of aggression, embraces, and kisses among female spider monkeys ( Ateles geoffroyi) in relation to group tenure. We recorded social interactions during 1688 10-min focal animal samples on 11 females in Santa Rosa, Costa Rica. We found that aggression was rare between long-term resident females and aggression rates were not higher during feeding than in other contexts, suggesting there was little contest competition. Long-term residents and less recently immigrant females showed higher aggression rates toward the most recent immigrants than toward other females, especially during the first months after a female immigrated, which coincided with the dry season. We did not find similar patterns for embrace and kiss. These results suggest that other females target aggression toward the most recent immigrants to reduce scramble competition. This finding suggests that group tenure should be included in socioecological models for species with female dispersal. [ABSTRACT FROM AUTHOR]

Fission-fusion dynamics are thought to be mainly a response to differential availability of food resources. However, social factors may also play a role. Here, we examined whether the quality of social relationships between group members affects fission decisions. During 21 months, we collected data on social interactions and fission events of 22 spider monkeys ( Ateles geoffroyi) living in a community in the protected area of Otoch Ma'ax Yetel Kooh, Yucatan, Mexico. By entering seven indexes of social interactions into a principal component analysis, we obtained three components of relationship quality, which we labelled 'compatibility,' 'value' and 'insecurity' given the relative loadings of the indexes. Our results showed that individuals were more likely to fission into the same subgroup with community members with whom they shared higher levels of compatibility and value and lower levels of insecurity. In addition, individuals preferred to fission into the same subgroup with same-sex group members, as expected based on what is known for the species. Our findings highlight the role of social factors in fission decisions. Adjustments in subgroup size are based on multifaceted social preferences, incorporating previously unexamined aspects of relationship quality, which are independent from overall levels of affiliative interactions. [ABSTRACT FROM AUTHOR]

One of the main costs of group living is feeding competition. Fission-fusion dynamics are thought to be a strategy to avoid overt competition for food resources. We tested whether food abundance and quality affected such dynamics in a species characterized by a high degree of fission-fusion dynamics. We collected data on 22 adult and subadult spider monkeys ( Ateles geoffroyi) living in a large community in the protected area of Otoch Ma'ax Yetel Kooh, Yucatan, Mexico. We recorded subgroup size and fission events as well as fruit abundance during 12 mo and conducted nutritional analyses on the fruit species that the study subjects consumed most. We found no effect of fruit abundance or nutritional quality of recently visited food patches on individual fission decisions, but the amount of protein in the food patches visited over the course of the day was a good predictor of subgroup size. While the absence of support for a relationship between fruit characteristics and fission decisions may be due to the short temporal scale of the analysis, our findings relating subgroup size to the amount of protein in the visited food patches over the course of the day may be explained by individual spider monkeys attempting to obtain sufficient protein intake from their fruit-based diet. [ABSTRACT FROM AUTHOR]

Ecological and social factors influence individual movement and group membership decisions, which ultimately determine how animal groups adjust their behavior in spatially and temporally heterogeneous environments. The mechanisms behind these behavioral adjustments can be better understood by studying the relationship between association and space use patterns of groups and how these change over time. We examined the socio-spatial patterns of adult individuals in a free-ranging group of spider monkeys (Ateles geoffroyi), a species with high fission-fusion dynamics. Data comprised 4916 subgroup scans collected during 325 days throughout a 20-month period and was used to evaluate changes from fruit-scarce to fruit-abundant periods in individual core-area size, subgroup size and two types of association measures: spatial (core-area overlap) and spatio-temporal (occurrence in the same subgroup) associations. We developed a 3-level analysis framework to distinguish passive associations, where individuals are mostly brought together by resources of common interest, from active association, where individuals actively seek or avoid certain others. Results indicated a more concentrated use of space, increased individual gregariousness and higher spatio-temporal association rates in the fruit-abundant seasons, as is compatible with an increase in passive associations. Nevertheless, results also suggested active associations in all the periods analyzed, although associations differed across seasons. In particular, females seem to actively avoid males, perhaps prompted by an increased probability of random encounters among individuals, resulting from the contraction of individual core areas. Our framework proved useful in investigating the interplay between ecological and social constraints and how these constraints can influence individual ranging and grouping decisions in spider monkeys, and possibly other species with high fission-fusion dynamics. [ABSTRACT FROM AUTHOR]

The article discusses the relationship between Central American spider monkeys and howler monkey species and the tropical plant bromeliads. The author offers information on a research which examines the behavior of the primates towards the plant which uses bromeliads as source of food and water supply considering that the monkeys are predominantly fruit eaters.

In most animal species, predation risk is considered the main factor affecting vigilance, and an individual is expected to spend less time vigilant in larger than in smaller groups. However, vigilance patterns in primates appear to differ, with no consistency in group-size effects. As individuals in highly gregarious species such as diurnal primates face frequent threats from group members, there may be increased vigilance in larger groups to monitor conspecifics rather than or in addition to predators. We tested this hypothesis in wild spider monkeys, which live in communities but fission and fuse in subgroups of variable size and membership throughout the same day. We found no overall effect of subgroup size, as traditionally measured, on vigilance. However, a possible explanation is that vigilance may be effectively shared only with individuals in close proximity, rather than with all subgroup members. We found that a larger number of neighbours (i.e., subgroup members within 5 m) was associated with a lower proportion of time individuals spent vigilant, which is similar to findings in other studies. Another social factor that may affect individuals' vigilance is the possibility of between-community encounters. Higher levels of vigilance can be expected in areas closer to the boundary of the home range, where between-community encounters are more likely to occur compared with non-boundary areas. We found that location in terms of boundary vs. non-boundary areas had a significant effect on the time individuals spent vigilant in the expected direction. We also found that location modulated the effect of subgroup size on vigilance: only in the boundary areas did larger subgroup sizes result in less individual vigilance time. We concluded that conspecifics affect vigilance of wild spider monkeys in multiple ways. [ABSTRACT FROM AUTHOR]

Aliphatic ketones are widely present in body-borne and food odors of primates. Therefore, we used an operant conditioning paradigm and determined olfactory detection thresholds in four spider monkeys for a homologous series of aliphatic 2-ketones (2-butanone to 2-nonanone) and two of their isomers (3- and 4-heptanone). We found that, with the exception of the two shortest-chained ketones, all animals detected concentrations <1 ppm (parts per million), and with five odorants individual animals even reached threshold values <0.1 ppm. Further, we found a significant correlation between olfactory sensitivity of the spider monkeys and carbon chain length of the 2-ketones which can best be described as a U-shaped function. In contrast, no significant correlation was found between olfactory sensitivity and position of the functional carbonyl group. Across-odorant and across-species comparisons revealed the following: spider monkeys are significantly less sensitive to the odors of aliphatic ketones than to the odor of other classes of aliphatic compounds (1-alcohols, n -aldehydes, n -acetic esters, and n -carboxylic acids) sharing the same carbon length. Spider monkeys do not differ significantly in their olfactory sensitivity for aliphatic ketones from squirrel monkeys and pigtail macaques, but are significantly less sensitive to these odorants compared to human subjects and mice. These findings support the notion that neuroanatomical and genetic properties do not allow for reliable predictions with regard to a species’ olfactory sensitivity. Further, we conclude that the frequency of occurrence of a class of odorants in a species’ chemical environment does not allow for reliable predictions of the species’ olfactory sensitivity. [ABSTRACT FROM AUTHOR]

Fecal glucocorticoid metabolites are increasingly used to investigate physiological stress. However, it is crucial for researchers to simultaneously investigate the effects of reproductive state because estradiol and placental hormones can affect circulating glucocorticoid concentrations. Reports on the relationships between glucocorticoids and reproductive state are inconsistent among females. Unlike several primate species that have heightened glucocorticoid activity during lactation, humans experience reduced glucocorticoid activity during lactation. Rather than a taxonomic difference, we hypothesize that this is a result of different environmental stressors, particularly the threat of infanticide. Here, we expand the number of wild primate species tested by validating a glucocorticoid assay for female Geoffroy's spider monkeys. We investigate the effects of reproductive state on their glucocorticoid concentrations. Utilizing a routine veterinary exam on a captive population, we determined that fecal glucocorticoid metabolites increase in response to a stressor (anesthesia), and this rise is detected approximately 24 hr later. Additionally, we found that extracted hormone patterns in a wild population reflected basic reproductive biology-estradiol concentrations were higher in cycling than lactating females, and in lactating females with older offspring who were presumably resuming their cycle. However, we found that estradiol and glucocorticoid concentrations were significantly correlated in lactating but not cycling females. Similarly, we found that reproductive state and estradiol concentration, but not stage of lactation, predicted glucocorticoid concentrations. Unlike patterns in several other primate species that face a relatively strong threat of infanticide, lactating spider monkeys experience reduced glucocorticoid activity, possibly due to attenuating effects of oxytocin and lower male-initiated aggression than directed at cycling females. More broadly, we conclude that future studies using fecal glucocorticoid metabolites to index stress should consider that reproductive state might confound glucocorticoid measurements. Am. J. Primatol. 77:925-935, 2015. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Studies of the gut microbiome have become increasingly common with recent technological advances. Gut microbes play an important role in human and animal health, and gut microbiome analysis holds great potential for evaluating health in wildlife, as microbiota can be assessed from non-invasively collected fecal samples. However, many common fecal preservation protocols (e.g. freezing at − 80 °C) are not suitable for field conditions, or have not been tested for long-term (greater than 2 weeks) storage. In this study, we collected fresh fecal samples from captive spider monkeys ( Ateles geoffroyi ) at the Columbian Park Zoo (Lafayette, IN, USA). The samples were pooled, homogenized, and preserved for up to 8 weeks prior to DNA extraction and sequencing. Preservation methods included: freezing at − 20 °C, freezing at − 80 °C, immersion in 100% ethanol, application to FTA cards, and immersion in RNAlater. At 0 (fresh), 1, 2, 4, and 8 weeks from fecal collection, DNA was extracted and microbial DNA was amplified and sequenced. DNA concentration, purity, microbial diversity, and microbial composition were compared across all methods and time points. DNA concentration and purity did not correlate with microbial diversity or composition. Microbial composition of frozen and ethanol samples were most similar to fresh samples. FTA card and RNAlater-preserved samples had the least similar microbial composition and abundance compared to fresh samples. Microbial composition and diversity were relatively stable over time within each preservation method. Based on these results, if freezers are not available, we recommend preserving fecal samples in ethanol (for up to 8 weeks) prior to microbial extraction and analysis. [ABSTRACT FROM AUTHOR]

Natural selection has resulted in the acoustic convergence of many animal vocalizations. During agonistic interactions vocalizations may vary depending on the role an individual plays in the interaction and on the severity of the attack. Motivation-structural rules describe how aggressors are thought to have evolved to use low-frequency vocalizations, whereas victims often use high-frequency vocalizations. This is because call frequency (Hz) is negatively related to body size across species. Motivational theory predicts that during more severe attacks, vocal structure will also change in response to increased arousal, leading to the production of noisy (high-entropy) vocalizations. Little is known about the acoustic characteristics of vocalizations produced during agonistic encounters in primates, and the limited available data are highly biased toward Old World species. Here, we evaluated the effect of the role of the emitter (aggressor or victim) and the severity of the behavior (with or without contact) on the acoustic parameters of 185 agonistic vocalizations emitted by 15 spider monkeys ( Ateles geoffroyi) in two captive groups. Our results supported the predictions of both the motivation-structural rules and motivational theory: Call frequency (Hz) was lower in aggressors than in victims and lower during high-severity encounters than low-severity encounters. Further, average entropy was higher during high-severity encounters. These findings suggest that the agonistic vocalizations of spider monkeys convey information about both the role of the emitter and the severity of the interaction. [ABSTRACT FROM AUTHOR]

In species in which males and females exhibit different association patterns, the use of vocalizations that regulate interindividual distance may differ between the sexes. Spider monkey social groups are characterized by high fission-fusion dynamics and sex differences in association patterns; female-female associations have been described as more passive than those between philopatric males. Individuals of both sexes produce whinny vocalizations, which may allow callers and receivers to mediate interindividual spacing based on existing social relationships. As such, we hypothesized individuals of each sex would use whinny vocalizations at different rates and in different contexts. To investigate sex differences in the rate of whinnying across behavioral contexts, we collected focal animal samples on Yucatan spider monkeys ( Ateles geoffroyi yucatanensis) over 8 mo at Runaway Creek Nature Reserve, Belize. In addition, we recorded all changes in subgroup composition to investigate whether a female's likelihood of calling was influenced by the number of conspecifics joining, or leaving their subgroup. We found that females called at higher rates than males in most behavioral contexts, especially foraging. The probability that females would call increased during subgroup fissions and fusions, and correlated positively with the number of individuals joining or leaving their subgroup. Male calling rates did not differ across contexts, and males generally called less than females. Our results suggest that whinnying by females may allow callers to mediate interindividual spacing in contexts where proximity risks increasing feeding competition. In species in which the sexes associate in qualitatively different ways, vocalizations may play a role in maintaining these differences. [ABSTRACT FROM AUTHOR]

Mesoamerican spider monkeys ( Ateles geoffroyi sensu lato) are widely distributed from Mexico to northern Colombia. This group of primates includes many allopatric forms with morphologically distinct pelage color and patterning, but its taxonomy and phylogenetic history are poorly understood. We explored the genetic relationships among the different forms of Mesoamerican spider monkeys using mtDNA sequence data, and we offer a new hypothesis for the evolutionary history of the group. We collected up to ∼800 bp of DNA sequence data from hypervariable region 1 (HV1) of the control region, or D-loop, of the mitochondrion for multiple putative subspecies of Ateles geoffroyi sensu lato. Both maximum likelihood and Bayesian reconstructions, using Ateles paniscus as an outgroup, showed that (1) A. fusciceps and A. geoffroyi form two different monophyletic groups and (2) currently recognized subspecies of A. geoffroyi are not monophyletic. Within A. geoffroyi , our phylogenetic analysis revealed little concordance between any of the classifications proposed for this taxon and their phylogenetic relationships, therefore a new classification is needed for this group. Several possible clades with recent divergence times (1.7–0.8 Ma) were identified within Ateles geoffroyi sensu lato. Some previously recognized taxa were not separated by our data (e.g., A. g. vellerosus and A. g. yucatanensis ), while one distinct clade had never been described as a different evolutionary unit based on pelage or geography ( Ateles geoffroyi ssp. indet. from El Salvador). Based on well-supported phylogenetic relationships, our results challenge previous taxonomic arrangements for Mesoamerican spider monkeys. We suggest a revised arrangement based on our data and call for a thorough taxonomic revision of this group. [ABSTRACT FROM AUTHOR]

Captive animals suffer from stress and lack of stimulation. Environmental enrichment (EE) provides them with a series of activities that encourages them to present species-specific behaviors. The objective of this work was to analyze the effect of an EE program in the behavior of a 7-spider monkey colony. It was expected that aggression, coprophilia and stereotypes would be less frequent, while exploration and play would increase. The study was divided in two stages: one previous to EE and one while EE was being implemented. A focal sampling per behavior was undertaken in 1-h continuous recordings for a total of 40 hours per stage. We compared the frequency of each behavior with a Wilcoxon's signal test. The results showed that aggression, stereotypes and coprophilia were reduced during EE, while exploration and play increased significantly. No significant differences were found between sexes. EE reduces the problems originated by confinement; therefore, it must be considered a necessary tool to be continuously employed to make an improvement into the life conditions of confined individuals. [ABSTRACT FROM AUTHOR]

New World monkeys exhibit prominent colour vision variation due to allelic polymorphism of the long-to-middle wavelength (L/M) opsin gene. The known spectral variation of L/M opsins in primates is broadly determined by amino acid composition at three sites: 180, 277 and 285 (the 'three-sites' rule). However, two L/M opsin alleles found in the black-handed spider monkeys ( Ateles geoffroyi) are known exceptions, presumably due to novel mutations. The spectral separation of the two L/M photopigments is 1.5 times greater than expected based on the 'three-sites' rule. Yet the consequence of this for the visual ecology of the species is unknown, as is the evolutionary mechanism by which spectral shift was achieved. In this study, we first examine L/M opsins of two other Atelinae species, the long-haired spider monkeys ( A. belzebuth) and the common woolly monkeys ( Lagothrix lagotricha). By a series of site-directed mutagenesis, we show that a mutation Y213D (tyrosine to aspartic acid at site 213) in the ancestral opsin of the two alleles enabled N294K, which occurred in one allele of the ateline ancestor and increased the spectral separation between the two alleles. Second, by modelling the chromaticity of dietary fruits and background leaves in a natural habitat of spider monkeys, we demonstrate that chromatic discrimination of fruit from leaves is significantly enhanced by these mutations. This evolutionary renovation of L/M opsin polymorphism in atelines illustrates a previously unappreciated dynamism of opsin genes in shaping primate colour vision. [ABSTRACT FROM AUTHOR]

Abstract: The gustatory responsiveness of four adult spider monkeys to the 20 proteinogenic amino acids was assessed in two-bottle preference tests of brief duration (1min). We found that Ateles geoffroyi responded with significant preferences for seven amino acids (glycine, l-proline, l-alanine, l-serine, l-glutamic acid, l-aspartic acid, and l-lysine) when presented at a concentration of 100mM and/or 200mM and tested against water. At the same concentrations, the animals significantly rejected five amino acids (l-tryptophan, l-tyrosine, l-valine, l-cysteine, and l-isoleucine) and were indifferent to the remaining tastants. Further, the results show that the spider monkeys discriminated concentrations as low as 0.2mM l-lysine, 2mM l-glutamic acid, 10mM l-proline, 20mM l-valine, 40mM glycine, l-serine, and l-aspartic acid, and 80mM l-alanine from the alternative stimulus, with individual animals even scoring lower threshold values. A comparison between the taste qualities of the proteinogenic amino acids as described by humans and the preferences and aversions observed in the spider monkeys suggests a fairly high degree of agreement in the taste quality perception of these tastants between the two species. A comparison between the taste preference thresholds obtained with the spider monkeys and taste detection thresholds reported in human subjects suggests that the taste sensitivity of A. geoffroyi for the amino acids tested here might match that of Homo sapiens. The results support the assumption that the taste responses of spider monkeys to proteinogenic amino acids might reflect an evolutionary adaptation to their frugivorous and thus protein-poor diet. [Copyright &y& Elsevier]

Communication and social relationships are two of the most important aspects of primate life, but few studies have focused on linking these aspects in apes. There are some shared social pressures between the two sexes (e.g., kin selection, alliance formation, and protection against attack), but there are also differences (e.g., mate selection, dispersal, and social ranking systems). The aim of this study was to identify the communication strategies of the sexes with respect to their particular communication partner. I hypothesized the sexes use different strategies in their gestural communication based on their different social pressures. Specifically, males should have more positive intra-sexual relationships than females because of high focus on male-male alliance formation and maintaining high social rank, both of which directly affect their mating opportunities and relationships with all other members of the group. On the other hand, females should have more positive inter-sexual relationships due to the abuse they could receive from insubordination to males and because there is less focus on maintaining multiple, positive relationships with other females. Furthermore, because of differences in social pressures, males should have higher incidence of reassurance in same-sex interactions than females because it should be more important for males to mitigate negative interactions. I analyzed the characteristics of the gesture repertoire and frequency of gesture use for each sex in each of four contexts: (1) aggression, (2) submission, (3) greeting, and (4) reassurance. I looked at intra-sexual and inter-sexual interactions, separately. I found that, indeed, males and females utilize different strategies of gestural communication. I also found that females, but not males, have a distinct gesture strategy for communicating with the opposite sex than for the same sex. This study shows there are distinct strategies utilized by the two sexes and these differences may be explained by their differing social pressures. Am. J. Primatol. 75:555-567, 2013. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Infant tolerance by adult males has been observed in many primate species with multimale-multifemale mating systems, but males do not usually initiate interactions with infants. In male philopatric species, such as spider monkeys, adult males within a community exhibit high levels of cooperation and affiliation, and they might therefore be motivated to create bonds with potential future allies. Based on this hypothesis we predicted that adult male spider monkeys would participate in infant handling more than adult females and they would preferentially direct handling toward male infants. Between January 2008 and July 2010, we collected 884 h of observation on a community of wild spider monkeys at Runaway Creek Nature Reserve in Belize. During this period we observed 120 incidences of affiliative interactions between infants and adults other than their mother. The adult initiated the majority of nonmother adult-infant interactions (78 %). All available infants (5 males, 7 females) were handled during the study. All 9 of the community adult males handled infants but only 7 of 14 adult females did so. Adult males handled infants significantly more often than did adult females and males also handled young infants more often than older infants. Significant infant sex differences in handling appeared in infants >6 mo when adult males handled males significantly more than females. The patterns of infant handling among age-sex class dyads reflect the affiliative social patterns that we see in adult spider monkeys. These results provide support for the hypothesis that adult males preferentially handle male infants as a strategy for fostering social bonds. [ABSTRACT FROM AUTHOR]

Core areas are thought to be critical parts of animal home ranges for sustaining the population, but few studies have tested this important assumption. We examined whether core areas of spider monkeys Ateles geoffroyi had better habitat quality than the rest of their home range (non-core areas). Habitat quality parameters, including density and diversity of food trees, degree of forest maturity and density of sleeping trees in core and non-core areas were analyzed using Moran eigenvector generalized linear model ( GLM) filtering using spatial eigenvector mapping to control for spatial autocorrelation. The best fitting GLM revealed that spider monkeys' core areas had higher habitat quality than non-core areas. This study provides quantitative evidence supporting the concept of core areas including the most critical resources for an animal population. In this respect, spider monkeys' core areas are a key to understand their movement ecology and habitat preferences. [ABSTRACT FROM AUTHOR]

Abstract: Using a conditioning paradigm, the olfactory sensitivity of six male CD-1 mice for “green odors”, a group of eight structurally related aliphatic C6 alcohols and aldehydes known to exert anxiolytic and stress-reducing effects, was investigated. With all eight stimuli, the animals discriminated concentrations ≤0.03ppm (parts per million) from the solvent, and with three of the eight stimuli the best-scoring animals were even able to detect concentrations ≤0.03ppb (parts per billion). Three female spider monkeys tested in parallel were found to detect the same eight stimuli at concentrations <1ppm, and with six of the eight stimuli the best-scoring animals detected concentrations ≤0.1ppm. Analysis of odor structure–activity relationships showed that in both species the type of functional group attached to the aliphatic C6 backbone of the odorant molecules systematically affected their olfactory sensitivity whereas the presence/absence of a double bond did not. In the mice, but not in the spider monkeys, the position of a double bond and the cis/trans-configuration of the odorant molecules also had a systematic effect on detectability of the “green odors”. A comparison of the detection thresholds between the two species tested here and those obtained in human subjects suggests that the number of functional olfactory receptor genes is a poor predictor of a species'' olfactory sensitivity for “green odors”. [Copyright &y& Elsevier]

Background It is unknown whether male black-handed spider monkeys ( Ateles geoffroyi) undergo a reproductive decline as they age. The purpose of this work was investigating whether serum testosterone and semen quality decrease with age in these primates as occur in other species. Methods In this study, we assessed age variations in the concentration of serum testosterone, sperm counts, and motility in nine males. We took serum blood samples and semen samples by electroejaculation of anesthetized males throughout the fertile season. Results We found that testosterone levels and total sperm concentration, motile, progressive, fast linearly moving, medium linearly moving, slow linearly moving and immotile sperm significantly decreased with age. Conclusions Our results show that a reproductive decline occurs in male spider monkeys because of a decrease in sperm counts. These results are similar to those of rhesus monkeys and men, despite the phylogenetic distance between New and Old World primates. [ABSTRACT FROM AUTHOR]

Understanding how primates adjust their behavior in response to seasonality in both continuous and fragmented forests is a fundamental challenge for primatologists and conservation biologists. During a 15-mo period, we studied the activity patterns of 6 communities of spider monkeys ( Ateles geoffroyi) living in continuous and fragmented forests in the Lacandona rain forest, Mexico. We tested the effects of forest type (continuous and fragmented), season (dry and rainy), and their interaction on spider monkey activity patterns. Overall, monkeys spent more time feeding and less time traveling in fragments than in continuous forest. A more leafy diet and the spatial limitations in fragments likely explain these results. Time spent feeding was greater in the rainy than in the dry season, whereas time spent resting followed the opposite pattern. The increase in percent leaves consumed, and higher temperatures during the dry season, may contribute to the observed increase in resting time because monkeys probably need to reduce energy expenditure. Forest type and seasonality did not interact with activity patterns, indicating that the effect of seasonality on activities was similar across all sites. Our findings confirm that spider monkeys are able to adjust their activity patterns to deal with food scarcity in forest fragments and during the dry season. However, further studies are necessary to assess if these shifts are adequate to ensure their health, fitness, and long-term persistence in fragmented habitats. [ABSTRACT FROM AUTHOR]

Seed dispersal is considered a key process determining spatial structure and dynamics of plant populations, and has crucial implications for forest regeneration. We evaluated the effectiveness of spider monkeys ( Ateles geoffroyi) as seed dispersers in continuous and fragmented habitats to test if this interaction is altered in forest fragments. We documented fruit and seed handling, defecation patterns, diversity and composition of seeds in feces, and seed germination of defecated and control seeds in the Lacandona rainforest, Mexico. For most species contributing to 80% of total fruit feeding time, monkeys swallowed and spat seeds, but swallowing was the most frequent seed handling category in continuous and fragmented forests. However, the proportion of feeding records of swallowed seeds was higher in continuous forest (0.59) than in fragments (0.46), whereas the opposite was true for proportion of dropped seeds (0.16 vs. 0.31). This pattern was reflected in the number of fecal samples containing seeds, which was greater in continuous (95.5%) than in fragmented forests (82.5%). Seeds in fecal samples included a total of 71 species from 23 plant families. The numbers of defecated seed species were similar between forest conditions, and in both cases most seeds (>86%) were undamaged. Defecated seeds showed greater germination percentages than control seeds in all of the five species evaluated. Although we identified some differences in seed handling and the percentage of feces with seeds between continuous forest and fragments, our results indicate that, in general terms, spider monkeys are effective seed dispersers in both forest conditions. [ABSTRACT FROM AUTHOR]

Abstract: Humans are subject to the composite illusion: two identical top halves of a face are perceived as “different” when they are presented with different bottom halves. This observation suggests that when building a mental representation of a face, the underlying system perceives the whole face, and has difficulty decomposing facial features. We adapted a behavioural task that measures the composite illusion to examine the perception of faces in two nonhuman species. Specifically we had spider (Ateles geoffroyi) and rhesus monkeys (Macaca mulatta) perform a two-forced choice, match-to-sample task where only the top half of sample was relevant to the task. The results of Experiment 1 show that spider monkeys (N =2) process the faces of familiar species (conspecifics and humans, but not chimpanzees, sheep, or sticks), holistically. The second experiment tested rhesus monkeys (N =7) with the faces of humans, chimpanzees, gorillas, sheep, and sticks. Contrary to prediction, there was no evidence of a composite effect in the human (or familiar primate) condition. Instead, we present evidence of a composite illusion in the chimpanzee condition (an unfamiliar primate). Together, these experiments show that visual expertise does not predict the composite effect across the primate order. [Copyright &y& Elsevier]

Gaze following is an adaptive skill that might have been selected in social species, such as many nonhuman primates, to obtain infonnation about food location, predators, and social interactions. The authors investigated the ability of spider monkeys (Ateles geoffroyi) and capuchin monkeys (Cebus apella) to follow the gaze of a human around barriers and the presence of "looking back" behavior. In the 1st experiment, a human looked to a target location inside the testing room, whereas in the 2nd experiment, the human looked behind an opaque barrier placed outside the testing room. The authors compared the frequency of looking at the target location with the corresponding baseline looking frequencies. Both species (a) showed evidence of sponta- neous gaze following in the 1st experiment and (b) engaged in gaze following behind the barrier in the 2nd experiment. In contrast, neither species performed "looking back" responses. The authors conclude that both monkey species showed some indication of perspective-taking abilities, although the absence of "looking back" behavior suggests a potential difference from the abilities shown by the great apes. [ABSTRACT FROM AUTHOR]

In the Yucatán Peninsula, spider monkeys Ateles geoffroyi yucatanensis are generally found in two contrasting conditions: large tracts of conserved forest or small fragments surrounded by human populations. In the present study, we analyzed fecal cortisol levels of spider monkeys to investigate whether environmental conditions have an influence on stress; specifically, we compared fecal cortisol across individuals living in conserved forests, fragmented forests and captive conditions (zoos and pets). Radioimmunoanalysis of fecal samples from 121 individuals indicated significant differences in mean cortisol for A. g. yucatanensis based on habitat type, with the lowest levels found in the conserved forest condition. The higher cortisol levels in both fragmented forest populations and in captive individuals may be the result of metabolic and behavioral stress. The mean male fecal cortisol concentration was significantly higher than that of females, and the fecal cortisol concentration was higher in the dry season compared with the wet season in a conserved habitat. Therefore, we emphasize the importance of considering sex and seasonality when monitoring fecal cortisol concentrations of spider monkeys, and more generally of frugivores, as they face a seasonal variation in food availability. Finally, our results suggest that forest fragmentation may create long-term stressors for spider monkeys, affecting the viability of populations living under such conditions. [ABSTRACT FROM AUTHOR]

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Trichromatic primates have a 'red-green' chromatic channel in addition to luminance and 'blue-yellow' channels. It has been argued that the red-green channel evolved in primates as an adaptation for detecting reddish or yellowish objects, such as ripe fruits, against a background of foliage. However, foraging advantages to trichromatic primates remain unverified by behavioral observation of primates in their natural habitats. New World monkeys (platyrrhines) are an excellent model for this evaluation because of the highly polymorphic nature of their color vision due to allelic variation of the L-M opsin gene on the X chromosome. In this study we carried out field observations of a group of wild, frugivorous black-handed spider monkeys (Ateles geoffroyi frontatus, Gray 1842, Platyrrhini), consisting of both dichromats (n = 12) and trichromats (n=9) in Santa Rosa National Park, Costa Rica. We determined the color vision types of individuals in this group by genotyping their L-M opsin and measured foraging efficiency of each individual for fruits located at a grasping distance. Contrary to the predicted advantage for trichromats, there was no significant difference between dichromats and trichromats in foraging efficiency and we found that the luminance contrast was the main determinant of the variation of foraging efficiency among red-green, blue-yellow and luminance contrasts. Our results suggest that luminance contrast can serve as an important cue in short-range foraging attempts despite other sensory cues that could be available. Additionally, the advantage of red-green color vision in primates may not be as salient as previously thought and needs to be evaluated in further field observations. [ABSTRACT FROM AUTHOR]

Using a conditioning paradigm, the olfactory sensitivity of four spider monkeys, three squirrel monkeys and three pigtail macaques to four thiols and two indols, substances characteristic of putrefaction processes and faecal odours, was assessed. With all odorants, the animals significantly discriminated concentrations below 1 p.p.m. (part per million) from the odourless solvent, and in several cases individual animals even demonstrated thresholds below 1 p.p.t. (part per trillion). The detection thresholds of 0.03 p.p.t. for indol in Saimiri sciureus and Macaca nemestrina and 0.96 p.p.t. for ethanethiol in Ateles geoffroyi represent the lowest values among the more than 50 odorants tested so far with these species and are in the same order of magnitude as the lowest detection thresholds reported so far in the rat and the mouse. The results showed (a) all three species of non-human primate to have a highly developed olfactory sensitivity for putrefaction-associated odorants, and (b) a significant correlation between perceptibility in terms of olfactory detection threshold and carbon chain length of the thiols, and a marked effect of the presence vs absence of a methyl group on perceptibility of the indols tested in two of the three species. The results support the hypotheses that (a) between-species differences in neuroanatomical or genetic features may not be indicative of olfactory sensitivity, and (b) within-species differences in olfactory sensitivity may reflect differences in the behavioural relevance of odorants. [ABSTRACT FROM AUTHOR]

I report three cases of coalitionary aggression by adult male black-handed spider monkeys (Ateles geoffroyi) against subadult males within their community on Barro Colorado Island (BCI), Panama. Two of these cases were followed by the disappearance and presumed death of the victim. Similar behavior was recently reported by Valero et al. [in press], who suggested that this behavior may be the result of intense male reproductive competition. Like the single instance they reported, the cases I report all occurred when the operational sex ratio was approximately 1:1, which suggests that intense competition among males for access to reproductively viable females may be a contributing factor. Additionally the very low density of spider monkeys on BCI may play a significant role in the occurrence of this lethal aggression. Large numbers of adult males are not necessary to protect a territorial boundary against neighboring groups, and additional males may act merely as mating competition. Am. J. Primatol. 68:1197–1201, 2006. © 2006 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

I report ad libitum data on 18 copulations involving free-ranging black-handed spider monkeys (Ateles geoffroyi) on Barro Colorado Island, Panama. All copulations were performed in a dorsoventral position, as is typically reported for this genus. Intromission often appeared difficult to achieve, possibly as a result of the large size of the glans penis in these animals. The average length from intromission to termination of thrusting exceeded 17 min, followed by an average period of almost 2 min before separation occurred, which suggests the possibility of a copulatory lock. Offspring of the female participant were almost always in close proximity to or in contact with the pair, and harassment by the offspring was observed only during the final stages of the copulation. All but one copulatory event occurred in complete seclusion from other adult males, and sexual behavior was not limited to any one adult male in the group. Am. J. Primatol. 68:1–5, 2006. © 2006 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Using a conditioning paradigm, the olfactory sensitivity of five spider monkeys for homologous series of aliphatic 1-alcohols (1-propanol to 1-octanol) and n-aldehydes (n-butanal to n-nonanal) was investigated. With the exception of 1-propanol, the animals significantly discriminated concentrations below 1 ppm from the odorless solvent, and in several cases, individual monkeys even demonstrated detection thresholds below 10 ppb. The results showed 1) spider monkeys to have a welldeveloped olfactory sensitivity for both substance classes, which for the majority of alcohols tested matches or even is better than that of the rat, and 2) a significant negative correlation between perceptibility in terms of olfactory detection thresholds and carbon chain length of the alcohols, but not of the aldehydes tested. These findings lend further support to the growing body of evidence suggesting that between-species comparisons of the number of functional olfactory receptor genes or of neuroanatomical features are poor predictors of olfactory performance, and that general labels such as "microsmat" or "macrosmat' (which are usually based on allometric comparisons of olfactory brain structures) are inadequate to describe a species' olfactory capabilities. [ABSTRACT FROM AUTHOR]

Ateles spp. and Alouatta spp. are often sympatric, and although they are mainly frugivorous and folivorous, respectively, they consume some of the same fruit species. However, they differ in terms of color vision, which is thought to be important for fruit detection. Alouatta spp. have routine trichromatic color vision, while Ateles spp. presents the classic polymorphism of platyrrhines: heterozygous females have trichromatic color vision, and males and homozygous females have dichromatic vision. Given these perceptual differences, one might expect Alouatta spp. to consume more reddish fruits than Ateles spp., since trichromats have an advantage for detecting fruits of that hue. Furthermore, since Ateles spp. have up to six different color vision phenotypes, as do most other platyrrhines, they might be expected to include fruits with a wider variety of hues in their diet than Alouatta spp. To test these hypotheses we studied the fruit foraging behavior of sympatric Alouatta palliata and Ateles geoffroyi in Costa Rica, and modeled the detectability of fruit via the various color vision phenotypes in these primates. We found little similarity in fruit diet between these two species (Morisita=0.086). Furthermore, despite its polymorphism, A. geoffroyi consumed more reddish fruits than A. palliata, which consumed more greenish fruits. Our modeling results suggest that most fruit species included in the diet of A. geoffroyi can be discriminated by most color vision phenotypes present in the population. These findings show that the effect of polymorphism in platyrrhines on fruit detection may not be a disadvantage for frugivory. We suggest that routine trichromacy may be advantageous for other foraging tasks, such as feeding on young leaves. Am. J. Primatol. 67:399–409, 2005. © 2005 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Although most arguments explaining the predominance of polymorphic color vision in platyrrhine monkeys are linked to the advantage of trichromacy over dichromacy for foraging for ripe fruits, little information exists on the relationship between nutritional reward and performance in fruit detection with different types of color vision. The principal reward of most fruits is sugar, and thus it seems logical to investigate whether fruit coloration provides a long-distance sensory cue to primates that correlates with sugar content. Here we test the hypothesis that fruit detection performance via trichromatic color vision phenotypes provides better information regarding sugar concentration than dichromatic phenotypes (i.e., is a color vision phenotype with sufficient red-green (RG) differentiation necessary to “reveal” the concentration of major sugars in fruits?). Accordingly, we studied the fruit foraging behavior of Ateles geoffroyi by measuring both the reflectance spectra and the concentrations of major sugars in the consumed fruits. We modeled detection performance with different color phenotypes. Our results provide some support for the hypothesis. The yellow-blue (YB) color signal, which is the only one available to dichromats, was not significantly related to sugar concentration. The RG color vision signal, which is present only in trichromats, was significantly correlated with sugar content, but only when the latter was defined by glucose. There was in fact a consistent negative relationship between fruit detection performance and sucrose concentration, although this was not significant for the 430 nm and 550 nm phenotypes. The regular trichromatic phenotypes (430 nm, 533 nm, and 565 nm) showed higher correlations between fruit performance and glucose concentration than the other two trichromatic phenotypes. Our study documents a trichromatic foraging advantage in terms of fruit quality, and suggests that trichromatic color vision is advantageous over dichromatic color vision for detecting sugar-rich fruits. Am. J. Primatol. 67:411–423, 2005. © 2005 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

The aim of this study was to characterize the circadian motor rhythm in the spider monkey, A. goeffroyi, in both entrained and free-running conditions. Four monkeys, 2 males and 2 females, were maintained for 32 days in constant light (LL) and 32 days in 13.25:10.75 LD. Before each experimental cycle, and between the LL and LD recordings, animals were maintained on 12:12 LD in their natural outdoor housing with the rest of their group. Each animal had its own Actiwatch collar for recording motor activity. The duration of the activity and rest periods and onset and offset of activity were averaged for each animal and in each condition. Recordings were analyzed with the ACTIWATCH program, and time series were analyzed with PGRAPH periodogram analyses. Actograms, histogram plots and periodograms were created for every subject. The data were also submitted to Fourier analysis using POTENCOR to determine circadian time and peaks under each experimental condition. Finally, Student's t-tests for paired samples were used to determine the differences between the artificial LL and natural LD conditions of every subject. A clear biphasic circadian pattern in the activity?–?rest cycle was observed in both conditions, confirmed by Fourier analysis with a periodicity of 24?h 01?min in LL. In LL the activity showed a dispersed temporal pattern with several small intermingled peaks, while the bimodal pattern of activity was more pronounced in LD with peaks at 08:11?h and 14:45?h. This data demonstrate the presence of a pacemaker with intrinsic ability to oscillate when the organism is under constant external conditions LL, that becomes entrained by the solar day when the animal is exposed to natural LD conditions. [ABSTRACT FROM AUTHOR]

Most platyrrhine monkeys have an X-linked tri-allelic polymorphism for medium and long wavelength (M/L) sensitive cone photopigments. These pigments' sensitivity maxima (λmax) range from 535 to 562 nm. All animals also have an autosomally coded short-wavelength-sensitive (S) cone pigment. In populations with three M/L alleles there are six different colour vision phenotypes. Heterozygous females have trichromatic colour vision, while males and homozygous females are dichromats. The selective basis for this polymorphism is not understood, but is probably affected by the costs and benefits of trichromatic compared to dichromatic colour vision. For example, it has been suggested that trichromats are better equipped than dichromats to detect fruit against a leaf background. To investigate this possibility, we modeled fruit detection by various colour vision phenotypes present in the frugivorous spider monkey, Ateles geoffroyi. Our study population is thought to have three M/L alleles with cone pigment λmax values close to 535, 550 and 562 nm. The model predicted that all trichromat phenotypes had an advantage over dichromats, and the 535/562 nm phenotype was best; however, the model predicted that dichromats could detect all of the fruit species consumed by spider monkeys. We conclude that the heterozygote advantage experienced by females may be the most plausible explanation for the maintenance of this polymorphism in A. geoffroyi. Nevertheless, more studies need to evaluate social foraging behaviour and the performance of different phenotypes of other New World monkeys to determine if this is a global explanation for this phenomena or more specific to A. geofforyi. [ABSTRACT FROM AUTHOR]

Members of the population of black-handed spider monkeys (Ateles geoffroyi ) on Barro Colorado Island, Panama, use the leaves of three Rutaceae species in a behavior that resembles fur rubbing in the white faced capuchin (Cebus capucinus ). This behavior has not been reported from other sites where Ateles has been studied. During more than 1,200 hours of observation, 30 episodes of this behavior were recorded ad libitum. Adult males engage in this behavior more than adult females. Season did not impact the frequency of the behavior. The behavior described here differs in many respects from that reported for Cebus capucinus , and does not fit the hypotheses that the behavior functions in repelling insects or other antiseptic purposes. It is proposed that fur rubbing in this group of spider monkeys is a modification of a behavior previously recorded in Ateles and may function in scent marking. Am. J. Primatol. 51:205–208, 2000. © 2000 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Our goal was to determine phylogenetic relationships among geographically and taxonomically distinct haplotypes of spider monkeys (Ateles ) based on DNA sequence variation for the mitochondrial DNA control region and cytochrome c oxidase subunit II gene. We obtained samples from most previously recognized subspecies of Ateles, ranging from Central America throughout the Amazon Basin, to determine phylogenetic relationships among racially recognized groups. Comparison of DNA sequences using both parsimony analysis and genetic distance analysis produced phylogenetic relationships that were very similar for each genetic region. We analyzed the phylograms produced, along with associated bootstrap support, confidence probabilities, and genetic distances between taxonomic groups, to identify four monophyletic species of Ateles: Ateles paniscus, composed of haplotypes from the northeastern Amazon Basin; A. belzebuth in the southern Amazon Basin; A. hybridus, located primarily along the Magdalena River valley of Colombia; and A. geoffroyi, which includes two former species: A. geoffroyi and A. fusciceps. This arrangement is contradictory to long-held taxonomies of Ateles based on pelage variation and is similar to a recent analysis based on craniodental variation. Results of this investigation suggest patterns of gene flow, evolutionary relationships, and speciation patterns that are more plausible than previous pelage-based taxonomies, which required seemingly impossible patterns of gene flow. Conservation efforts aimed at protecting Ateles, one of the Neotropics most endangered genera, will also benefit from the findings presented in this paper. [ABSTRACT FROM AUTHOR]

Tests the hypothesis that Colobus guereza and Ateles geoffroyi, have a first metacarpal whose length is both highly variable relative to the lengths of the other metapodials. Variability of vestigial structure; Characteristics of vestigial pollex in primates; Definitions of vestigiality.

The ovarian cycles of four adult female spider monkeys (Ateles geoffroyi ) were followed daily throughout 30 days by means of vaginal swabs and blood samplings. Cytological analyses of the vaginal swabs and radioimmunoassay determination of the daily levels of estradiol-17β (E[sub 2] ) and progesterone (P[sub 4] ) were done in order to classify the kind of ovarian cycle of this species. Our results show that Ateles geoffroyi females display menstrual cycles of about 24 days on average. By comparison with the well-known menstrual cycles of women, apes, and Old World monkeys, the four distinctive cytological phases (bleeding, follicular, periovulatory, and luteal) could be recognized; mid-cycle E[sub 2] peaks followed by mid-luteal increases of the same hormone were present in all four females. P[sub 4] levels were higher after the E[sub 2] peak, although both hormones were present throughout the cycles. Also, age-dependent features, hormone profiles, and changes in menstrual phases lengths were detected. Am. J. Primatol. 44:183–195, 1998. © 1998 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Although radio tracking has been used increasingly in primate field studies over the past 15 years, some primatologists have been reluctant to use it. We present data that demonstrate benefits of radio tracking in the study of rain forest primates. Data were collected during an ecological study of Ateles geoffroyi and Cebus capucinus in hilly, dense rain forest habitat with poor visibility, in northeastern Costa Rica. We show that radio tracking decreased search time for both species, which led to in- creased contact time and facilitated continuous data collection. Mean search time for both primate species was significantly reduced using radio tracking (Kruskal-WaIlis Test, P Although radio tracking has been used increasingly in primate field studies over the past 15 years, some primatologists have been reluctant to use it. We present data that demonstrate benefits of radio tracking in the study of rain forest primates. Data were collected during an ecological study of Ateles geoffroyi and Cebus capucinus in hilly, dense rain forest habitat with poor visibility, in northeastern Costa Rica. We show that radio tracking decreased search time for both species, which led to in- creased contact time and facilitated continuous data collection. Mean search time for both primate species was significantly reduced using radio tracking (Kruskal-WaIlis Test, P < 0.05). Search times for both species increased at the end of the study, when the transmitters ceased functioning. These increased search times occurred despite high levels of familiarity with the ranging patterns of the animals. The rate of marking feeding trees increased significantly with radio tracking and decreased significantly when the radios failed (Kruskal-Wallis Test, P < 0.01). [ABSTRACT FROM AUTHOR]

Presents information on the study which examines vertebral form and function in atelines and cebines. Combination of direct field observations of axial postures and movements, assessments of spinal loading regimes; Detailed information on a vertebral morphometric analysis; Information on field observations on Ateles geoffroyi, Alouatta palliata, Cebus capucinus, and Saimiri oerstedii.

Describes the results of a quantitative study of cranial ontogeny in male and female Ateles geoffroyi. Use of the Euclidean Distance Matrix Analysis (EDMA); Change local to the zygomatic region in the face; Identification of mediolaterally directed changes in the palate.

Diel activity rhythms in mammals are regulated by an endogenous (circadian) timing system which is synchronized by environmental 24‐hr periodicities called zeitgebers. Additional direct responses to stochastic environmental factors ensure the fine‐tuning to the actual situation and may mask the circadian time course. Following an observational study on behavioral effects of visitor activities in a group of spider monkeys (Ateles geoffroyi) kept free‐ranging on a small island of Lake Catemaco, Veracruz, Mexico, we analyzed the effect of weekly varying numbers of visiting tourist boats on the monkeys' diel activity rhythm. With small accelerometer‐data logger devices we recorded the monkeys' locomotor activity continuously for several months each. Then we compared the data with those from spider monkeys living without tourist contact. Neither the duration of the monkeys' activity time (α) nor its phase relationship to the 24‐hr solar day did change on different weekdays in either site. However, their activity level showed a clear 7‐day rhythm. The monkeys of the tourist site showed highest activity on Saturday and Sunday, when the frequency of visiting tourist boats was highest, whereas those of the non‐tourist site were least active on Sunday and Monday, when human activities were lowest there. While the monkeys of the non‐tourist site usually displayed a distinct bimodal activity pattern peaking in the morning and late afternoon, the pattern in those of the tourist site mostly lacked a morning peak and varied more over time. Based on our results, we suggest that circadian entrainment is not involved in the differences between the diel activity rhythms of the spider monkeys from the two keeping sites and the differing 7‐day variation in their activity level. Rather, these differences seemingly reflect direct responses to the differing human activities and thus may correspond to circadian masking effects. Spider monkeys respond to the presence of tourists by modifying their pattern of circadian activity. Infradian rhythm represent a positive masking effect of human activity, superimposed on monkeys' naturally entrained circadian activity rhythm. [ABSTRACT FROM AUTHOR]