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Concept: Black-headed Spider Monkey


Animal home ranges may vary little in their size and location in the short term but nevertheless show more variability in the long term. We evaluated the degree of site fidelity of two groups of spider monkeys (Ateles geoffroyi) over a 10- and 13-year period, respectively, in the northeastern Yucatan peninsula, Mexico. We used the Local Convex Hull method to estimate yearly home ranges and core areas (defined as the 60% probability contour) for the two groups. Home ranges varied from 7.7 to 49.6 ha and core areas varied from 3.1 to 9.2 ha. We evaluated the degree of site fidelity by quantifying the number of years in which different areas were used as either home ranges or core areas. Large tracts were used only as home ranges and only for a few years, whereas small areas were used as either core area or home range for the duration of the study. The sum of the yearly core areas coincided partially with the yearly home ranges, indicating that home ranges contain areas used intermittently. Home ranges, and especially core areas, contained a higher proportion of mature forest than the larger study site as a whole. Across years and only in one group, the size of core areas was positively correlated with the proportion of adult males in the group, while the size of home ranges was positively correlated with both the proportion of males and the number of tree species included in the diet. Our findings suggest that spider monkey home ranges are the result of a combination of long-term site fidelity and year-to-year use variation to enable exploration of new resources.

Concepts: Time, Primate, Term, Atelidae, Home range, Spider monkey, Geoffroy's Spider Monkey, Black-headed Spider Monkey


The presentation of food may affect feeding competition and the well-being of captive social species. We hypothesized that feeding competition in a captive group of 5 black-handed spider monkeys (Ateles geoffroyi) should increase in response to certain food presentations in terms of size, distribution and quality of food, and that higher feeding competition should lead to an increase in agonism and physiological stress (measured by faecal glucocorticoid metabolites, FGCM) as well as to a decrease in affiliation, proximity among individuals and feeding activity. We used 5 experimental treatments representing different combinations of size, distribution and quality of food. We observed social interactions for 100 h, collected 6,500 proximity and feeding activity records, and gathered 226 faecal samples. When food was clumped, individuals spent less time feeding, and there was also significant individual variation in feeding activity within treatments. FGCM levels were higher when food was clumped. These results are probably linked to an increase in feeding competition when food is concentrated. At least in small groups of spider monkeys, dispersing food in two feeding stations may be sufficient to decrease differences among individuals in priority of access to food resources, hence reducing physiological stress and interindividual differences in feeding activity.

Concepts: Primate, Hypothesis, Stress, Presentation, Atelidae, Spider monkey, Geoffroy's Spider Monkey, Black-headed Spider Monkey


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.

Concepts: Bacteria, Biotechnology, Primate, Food preservation, Atelidae, Spider monkey, Geoffroy's Spider Monkey, Black-headed Spider Monkey


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.

Concepts: Primate, Acoustics, Length, Distance, Elementary mathematics, Atelidae, Spider monkey, Black-headed Spider Monkey


The fast movement and high degree of fission-fusion dynamics of spider monkeys (Ateles spp.) make them notoriously difficult to survey. We examined which aspects of survey design affect spider monkey sightings along transects in a group of individually recognized spider monkeys (Ateles geoffroyi) in Punta Laguna, Yucatan, Mexico. We calculated the number of monkeys and subgroups sighted per transect walk. Using generalized linear models, we found no effect of the number of observers, transect type (new vs. existing), walking speed, or time of day on individual monkey counts or subgroup counts. Recounting of individuals was relatively rare and occurred when transects were walked relatively slowly. We missed more young than adult monkeys. The group composition based on survey data was similar to the known group composition. Based on our findings we recommend that surveys performed on relatively flat terrain be conducted at speeds similar to or faster than the moving speed of spider monkeys to minimize recounting of individuals and that young:adult female ratios based on survey data be interpreted as conservative indicators of population health. The novel methods presented to determine sources of bias in population estimates are applicable to a wide range of primates that are difficult to survey.

Concepts: Primate, Group theory, Walking, Atelidae, Spider monkey, Geoffroy's Spider Monkey, Atelinae, Black-headed Spider Monkey


Behavioral laterality refers to a bias in the use of one side of the body over the other and is commonly studied in paired organs (e.g., hands, feet, eyes, antennae). Less common are reports of laterality in unpaired organs (e.g., trunk, tongue, tail). The goal of the current study was to examine tail use biases across different tasks in the Colombian spider monkey (Ateles fusciceps rufiventris) for the first time (N = 14). We hypothesized that task context and task complexity influence tail laterality in spider monkeys, and we predicted that monkeys would exhibit strong preferences for using the tail for manipulation to solve out-of-reach feeding problems, but not for using the tail at rest. Our results show that a subset of spider monkeys solved each of the experimental problems through goal-directed tail use (N = 7). However, some tasks were more difficult than others, given the number of monkeys who solved the tasks. Our results supported our predictions regarding laterality in tail use and only partially replicated prior work on tail use preferences in Geoffroy’s spider monkeys (Ateles geoffroyi). Overall, skilled tail use, but not resting tail use, was highly lateralized in Colombian spider monkeys. (PsycINFO Database Record

Concepts: Scientific method, Primate, Atelidae, Spider monkey, Geoffroy's Spider Monkey, Spider monkeys and woolly monkeys, Black-headed Spider Monkey


We analyzed the effect of human visitors on the behavior of a group of spider monkeys (Ateles geoffroyi) kept on a small tourist island. Although the spider monkey is a common species in zoos, there are very few specific studies on visitor effects on these monkeys. We conducted behavioral observations on the group of spider monkeys to evaluate the effect of visitors. We also used actimetry devices to measure the variations in the spider monkeys' locomotor activity associated with human presence. With regard to the effect on behavior, we found an increase in self-directed behaviors and a decrease in vocalization, both associated with human presence. Moreover, our results suggest that when people feed monkeys, there is an increase in agonistic behaviors. On the other hand, we found that changes in activity levels in response to human presence vary among individuals. We conclude that changes in spider monkeys' behavior could provide evidence of the negative effect of visitors in our study conditions. Although we discuss the differences in activity levels due to differences in social position, further research is required this topic. Our results can be used to inform management plans for this species in captivity. Improving this relationship between humans and non-human primates through tourism education programs would benefit ecotourism and therefore species conservation programs.

Concepts: Psychology, Human, Primate, Behavior, Atelidae, Spider monkey, Geoffroy's Spider Monkey, Black-headed Spider Monkey


The physiological mechanisms that allow for sleeping in a vertical position, which is primordial for arboreal primates, have not been studied yet.

Concepts: Sleep, Electroencephalography, Primate, Atelidae, Spider monkey, Geoffroy's Spider Monkey, Arboreal theory, Black-headed Spider Monkey


The vertebral heart score (VHS) is a method of evaluation of cardiac size well documented in domestic mammals and in other primate species, and the aim of this study was to determine the VHS in three species of Spider monkey.

Concepts: Human, Heart, Mammal, Primate, Atelidae, Spider monkey, Geoffroy's Spider Monkey, Black-headed Spider Monkey


Side biases observed in behavior are thought to reflect underlying asymmetric brain function or hemispheric specialization. Previous work in multiple species identified left side biases (associated with the right hemisphere) for processing social behavior. In highly social species such as primates, many behaviors may be categorized as social, yet differences between such behaviors have not been examined as a test of asymmetric brain function. Using Colombian spider monkeys (Ateles fusciceps rufiventris), we observed lateral positioning during two types of behaviors widely categorized as social affiliative: embracing and grooming, and identified a left bias for embracing, but not grooming. Our findings partially support prior research in hemispheric specialization, but suggest that there may be differences between social behaviors that drive specialization. We discuss these results in light of current theory on hemispheric specialization and highlight differences between embracing and grooming.

Concepts: Scientific method, Psychology, Primate, Human behavior, Social behavior, Atelidae, Spider monkey, Black-headed Spider Monkey