Rapid facial mimicry in Platyrrhini: Play face replication in spider monkeys (Ateles fusciceps, Ateles hybridus, and Ateles paniscus)

Rapid facial mimicry (RFM), the rapid and automatic replication of facial expression perceived, is considered a basic form of empathy and was investigated mainly during play. RFM occurs in Catarrhini (Old World primates), but it is not still demonstrated in Platyrrhini (New World primates). For this reason, we collected video data on playful interactions (Nplay_interactions = 149) in three species of spider monkeys (Ateles fusciceps-N = 11, Ateles hybridus-N = 14, and Ateles paniscus-N = 6) housed at La Vallée des Singes and the ZooParc de Beauval (France). For the first time, we demonstrated the occurrence of RFM in Platyrrhini (analyzing 175 events). Players' sex, age, species, relationship quality, and kinship did not modulate RFM probably due to the species' complex fission-fusion dynamics and flexible interindividual social relationships. Compared to the absence of any playful expressions or the presence of only not replicated play face, RFM prolonged the session duration and was sequentially associated with more types of more intense offensive playful patterns (patterns aimed at attacking/pursuing the playmate). We proposed that RFM may favor synchronization and context sharing between players, thus decreasing the risk of behavior misinterpretation while simultaneously fostering a more competitive nature of play. In conclusion, this study stimulates additional research on the evolutionary origins of motor mimicry in primates, possibly dating back to before the divergence of New and Old World monkeys. Furthermore, it also points toward the possibility that RFM may not always lead to cooperation but also to competition, depending on the context and species' social and cognitive features.

Variation of thoracolumbar vertebral morphology in anthropoid primates

OBJECTIVES

Morphological variation among extant primates in the lumbar vertebral column is well studied. However, knowledge concerning the thoracic spine, an important region responsible for supporting and facilitating movement in the upper trunk, remains relatively scarce. Consequently, our comprehension of the functional differentiation exhibited throughout the thoracolumbar vertebral column among various primate species remains constrained. In this study, we examined patterns of morphological variation in the thoracolumbar vertebral column of extant hominoids, cercopithecoids, and Ateles.

MATERIALS AND METHODS

We collected external shape data on 606 thoracic and lumbar vertebrae from Homo sapiens, Pan troglodytes, Hylobates lar, Macaca fuscata, Chlorocebus aethiops, Colobus guereza, Ateles geoffroyi, and A. belzebuth. Forty-four landmarks were obtained on the three-dimensional surface. Geometric morphometrics was used to quantify the centroid size and variation of the shapes of thoracic and lumbar vertebrae.

RESULTS

Cercopithecoids exhibited greater variation in the size and shape of their thoracic and lumbar vertebrae compared to hominoids and Ateles. Although many vertebral features contributed to the observed variation throughout the thoracolumbar vertebral column within the taxon, the transverse and spinous processes exhibited relatively major contributions.

DISCUSSION

Our results suggest that quadrupedal locomotion requires the functional differentiation between thoracic and lumbar vertebrae, and for hominoids, functional adaptation to orthograde posture necessitates a relatively more uniform shape of thoracic and lumbar vertebrae.

Let's not use it! A dynamic no-use zone between the home ranges of two spider monkey groups

It is common that neighboring groups of the same species use some of the same areas, resulting in home-range overlap. Areas between the home ranges of neighboring groups not used by either group (no-use zone or NUZ) are rarely reported. Here, we report the existence of a NUZ between the home ranges of two Geoffroy's spider monkey groups, and examine its spatial changes over time and the ecological and behavioral underpinnings of such phenomenon. Although its size and location changed between 2017 and 2022, the NUZ was always present. We did not find any differences in the vegetation structure and composition between the NUZ and the ranging areas and in the monkeys' activity patterns between areas adjacent to the NUZ and the other parts of the ranging areas. The number of monkey vocalizations was lower and subgroup size was smaller (although the number of males did not differ) in areas adjacent to the NUZ than in the other parts of the ranging areas. Both changes possibly reflect the tendency to conceal their presence to the neighboring group. Our findings contribute to the understanding of primate space use and highlight the need to focus on the areas delimiting home ranges.

SARS-CoV-2 infection in brown-headed spider monkeys (Ateles fusciceps) at a wildlife rescue center on the coast of Ecuador-South America

Human populations can be affected in unpredictable ways by the emergence and spread of zoonotic diseases. The COVID-19 (coronavirus disease of 2019) pandemic was a reminder of how devastating these events can be if left unchecked. However, once they have spread globally, the impact of these diseases when entering non-exposed wildlife populations is unknown. The current study reports the infection of brown-headed spider monkeys (Ateles fusciceps) at a wildlife rescue center in Ecuador. Four monkeys were hospitalized, and all tested positive for SARS-CoV-2 (Severe acute respiratory syndrome coronavirus 2) by RT-qPCR (Quantitative Reverse Transcription PCR). Fecal samples (n = 12) from monkeys at the rescue center also tested positive; three zookeepers responsible for feeding and deworming the monkeys also tested positive, suggesting human-animal transmission. Whole genome sequencing identified most samples' omicron clade 22B BA.5 lineage. These findings highlight the threat posed by an emerging zoonotic disease in wildlife species and the importance of preventing spillover and spillback events during epidemic or pandemic events.IMPORTANCEAlthough COVID-19 (coronavirus disease of 2019) has been primarily contained in humans through widespread vaccination, the impact and incidence of SARS-CoV-2 (Severe acute respiratory syndrome coronavirus) and its transmission and epidemiology in wildlife may need to be addressed. In some natural environments, the proximity of animals to humans is difficult to control, creating perfect scenarios where susceptible wildlife can acquire the virus from humans. In these places, it is essential to understand how transmission can occur and to develop protocols to prevent infection. This study reports the infection of brown-headed spider monkeys with SARS-CoV-2, a red-listed monkey species, at a wildlife recovery center in Ecuador. This study reports the infection of brown-headed spider monkeys with SARS-CoV-2, indicating the potential for transmission between humans and wildlife primates and the importance of preventing such events in the future.

First whole-genome sequence and assembly of the Ecuadorian brown-headed spider monkey (Ateles fusciceps fusciceps), a critically endangered species, using Oxford Nanopore Technologies

The Ecuadorian brown-headed spider monkey (Ateles fusciceps fusciceps) is currently considered one of the most endangered primates in the world and is classified as critically endangered [International union for conservation of nature (IUCN)]. It faces multiple threats, the most significant one being habitat loss due to deforestation in western Ecuador. Genomic tools are keys for the management of endangered species, but this requires a reference genome, which until now was unavailable for A. f. fusciceps. The present study reports the first whole-genome sequence and assembly of A. f. fusciceps generated using Oxford Nanopore long reads. DNA was extracted from a subadult male, and libraries were prepared for sequencing following the Ligation Sequencing Kit SQK-LSK112 workflow. Sequencing was performed using a MinION Mk1C sequencer. The sequencing reads were processed to generate a genome assembly. Two different assemblers were used to obtain draft genomes using raw reads, of which the Flye assembly was found to be superior. The final assembly has a total length of 2.63 Gb and contains 3,861 contigs, with an N50 of 7,560,531 bp. The assembly was analyzed for annotation completeness based on primate ortholog prediction using a high-resolution database, and was found to be 84.3% complete, with a low number of duplicated genes indicating a precise assembly. The annotation of the assembly predicted 31,417 protein-coding genes, comparable with other mammal assemblies. A reference genome for this critically endangered species will allow researchers to gain insight into the genetics of its populations and thus aid conservation and management efforts of this vulnerable species.

Gestural communication in wild spider monkeys (Ateles geoffroyi)

Gestures play a central role in the communication systems of several animal families, including primates. In this study, we provide a first assessment of the gestural systems of a Platyrrhine species, Geoffroy's spider monkeys (Ateles geoffroyi). We observed a wild group of 52 spider monkeys and assessed the distribution of visual and tactile gestures in the group, the size of individual repertoires and the intentionality and effectiveness of individuals' gestural production. Our results showed that younger spider monkeys were more likely than older ones to use tactile gestures. In contrast, we found no inter-individual differences in the probability of producing visual gestures. Repertoire size did not vary with age, but the probability of accounting for recipients' attentional state was higher for older monkeys than for younger ones, especially for gestures in the visual modality. Using vocalizations right before the gesture increased the probability of gesturing towards attentive recipients and of receiving a response, although age had no effect on the probability of gestures being responded. Overall, our study provides first evidence of gestural production in a Platyrrhine species, and confirms this taxon as a valid candidate for research on animal communication.

Taphonomy of harpy eagle predation on primates and other mammals

The goal of this study is to provide a taphonomic analysis of bone fragments found in harpy eagle nests in the Brazilian Amazonia, utilizing the largest sample of prey remains collected to date. Harpy eagle kill samples were collected from nine nests, between June 2016 and December 2020 in Mato Grosso, Brazil. We identified the specimens, calculated the number of identified specimens (NISP) and minimum number of individuals (MNI). These metrics were used to estimate bone survivability and fragmentation. A total of 1661 specimens (NISP) were collected, representing a minimum number of 234 individuals (MNI). We identified at least nine species of primates, which represent 63.8% of the individuals in the kill sample. Harpy eagles preyed mostly on the medium-sized capuchin and bearded saki monkeys (28.2% of the MNI), and two-toed sloths (17.7% of the MNI). The large woolly monkeys also represented a significant portion of the sample (11.5% of the MNI). Three distinct patterns of bone survivability were found, one characterizing two-toed sloths, another characterizing medium-sized monkeys, and a third typical of woolly monkeys. We conclude that harpy eagle predation leaves an identifiable signature on the prey with a bone survivability pattern specific to each taxon. The intertaxon variations observed in the taphonomic signatures of harpy eagle kills should be taken into account when evaluating the potential influence of these raptors as accumulators of bone material in both paleontological and neontological assemblages.

CAMPYLOBACTER HYOINTESTINALIS ISOLATION FROM HOWLER (ALOUATTA CARAYA) AND SPIDER MONKEYS (ATELES FUSCICEPS ROBUSTUS) AT A ZOOLOGIC FACILITY IN CENTRAL ILLINOIS

Campylobacter hyointestinalis was initially isolated from an asymptomatic black howler monkey (Alouatta caraya) in a routine fecal culture examination. Fecal cultures from other individuals in this group and an adjacently housed black-headed spider monkey (Ateles fusciceps robustus) group recovered C. hyointestinalis from all but one of the individuals sampled (1.1 spider monkeys and 2.1 howler monkeys). Concurrently, one spider monkey presented with acute onset severe rectal prolapse and diarrhea. Whole-genome sequencing results of C. hyointestinalis isolates from all individuals were homologous and closely related to Campylobacter hyointestinalis subsp. hyointestinalis TTU_618, a strain typically associated with environmental samples. In addition, two cytolethal distending toxin (CDT) expressing gene clusters, cdt-I and cdt-II, were identified in all isolates. These results suggest C. hyointestinalis is transmissible to both howler monkeys and spider monkeys, though the origin of infection and whether it is transmissible between these species is undetermined.

Vigilance has mainly a social function in a wild group of spider monkeys (Ateles geoffroyi)

Vigilance is a widespread behavior that allows individuals to socially acquire information and/or effectively detect potential risks posed by predators and conspecifics. In this study, we aimed to investigate how social factors (i.e., subgroup size, number of males and immatures in the subgroup, presence of fission and fusion events, subgroup activity), individual characteristics (i.e., sex, presence of dependent offspring) and possible vulnerability to predation (i.e., being in smaller subgroups or lower in the canopy) explain variation in vigilance behavior in a wild group of spider monkeys (Ateles geoffroyi). We collected vigilance data during focal samples of all adults, subadults and juveniles of the group (N = 38), and ran generalized linear mixed models with a Bayesian approach. We found that the proportion of time both sexes spent in vigilance increased with subgroup size and during fusion events. Individuals also spent more time in vigilance when the subgroup was resting or socializing compared to other activities. Moreover, the proportion of time spent in vigilance increased in subgroups with more immatures. An alternative model with similar fit suggested that the proportion of time spent in vigilance increased in females when subgroups included more adult and subadult males. Overall, these results suggest that our study group mainly directed vigilance toward conspecifics (i.e., social vigilance), probably as a result of the relatively low predation pressure experienced, and contribute to the understanding of the multiple social factors affecting vigilance in group-living primates.

Estimating the impact of the illegal trade of primates in Mexico: a potential threat to wildlife

The primates of Mexico, Ateles geoffroyi, Alouatta palliata, and Alouatta pigra, are seriously threatened by habitat loss, fragmentation, and illegal hunting and trade. Very little is known about the extent of illegal trade and its impacts on declining primate populations. Our study proposes a potential method based on estimating the number of individuals that die in the trade before being detected and those that probably cannot be detected. This facilitates estimating the number of animals extracted and allows an assessment of how trafficking impacts their populations. We derive estimates from seizure data of primates in Mexico between 2010 and 2019. To do this, we created wildlife detection rates and mortality rates from the existing literature (scientific articles, journalistic articles, and notes) to estimate the number of primates that die during capture, transport, and sale and the number of trafficked primates that were not detected by Mexican authorities. We estimate that 946 primates were removed from the wild for the pet trade each year (spider monkey Ateles geoffroyi = 854; black howler monkeys Alouatta pigra = 38, mantled howler monkey Alouatta palliata = 54). The annual reduction in population size caused by trafficking was greatest for Ateles geoffroyi (2.2%), followed by Alouatta pigra (1.3%), and Alouatta palliata (0.4%). Our estimates show the percentage of impacts that trafficking has on Mexican primate populations. Nevertheless, trade has the potential to impact declining populations and still must be addressed.

Primate richness and abundance is driven by both forest structure and conservation scenario in Costa Rica

Variation in tropical forest management directly affects biodiversity and provisioning of ecosystem services on a global scale, thus it is necessary to compare forests under different conservation approaches such as protected areas, payments for ecosystem services programs (PES), and ecotourism, as well as forests lacking any formal conservation plan. To examine the effectiveness of specific conservation approaches, we examined differences in forest structure and tree recruitment, including canopy cover; canopy height; seedling, sapling, and adult tree density; and average and total diameter at breast height (DBH) across 78 plots in 18 forests across Costa Rica representing protected areas, private forests utilizing PES and/or ecotourism, and private forests not utilizing these economic incentives. The effectiveness of conservation approaches in providing suitable primate habitat was assessed by conducting broad primate census surveys across a subset of eight forests to determine species richness and group encounter rate of three primate species: mantled howler monkey (Alouatta palliata), Central American spider monkey (Ateles geoffroyi), and the white-faced capuchin monkey (Cebus imitator). Only canopy height was significantly different across the three approaches, with protected areas conserving the tallest and likely oldest forests. Canopy height was also significantly associated with the group encounter rate for both mantled howler and spider monkeys, but not for capuchins. Total group encounter rate for all three monkey species combined was higher in incentivized forests than in protected areas, with capuchin and howler monkey group encounter rates driving the trend. Group encounter rate for spider monkeys was higher in protected areas than in incentivized forests. Incentivized conservation (PES and ecotourism) and protected areas are paragons of land management practices that can lead to variation in forest structure across a landscape, which not only protect primate communities, but support the dietary ecologies of sympatric primate species.

Memetic Spider Monkey Optimization for Spam Review Detection Problem

Spider monkey optimization (SMO) algorithm imitates the spider monkey's fission-fusion social behavior. It is evident through literature that the SMO is a competitive swarm-based algorithm that is used to solve difficult real-life problems. The SMO's search process is a little bit biased by the random component that drives it with high explorative searching steps. A hybridized SMO with a memetic search to improve the local search ability of SMO is proposed here. The newly developed strategy is titled Memetic SMO (MeSMO). Further, the proposed MeSMO-based clustering approach is applied to solve a big data problem, namely, the spam review detection problem. A customer usually makes decisions to purchase something or make an image of someone based on online reviews. Therefore, there is a good chance that the individuals or companies may write spam reviews to upgrade or degrade the stature or value of a trader/product/company. Therefore, an efficient spam detection algorithm, MeSMO, is proposed and tested over four complex spam datasets. The reported results of MeSMO are compared with the outcomes obtained from the six state-of-art strategies. A comparative analysis of the results proved that MeSMO is a good technique to solve the spam review detection problem and improved precision by 3.68%.

Convergence between G and g in three monkey species (Sapajus spp, Ateles geoffroyi, and Macaca fascicularis)

An open question in comparative psychology is whether the source of correlations among different measures of ability (the g factor) is shared between species, or is distinct. This is examined using data on the performance of three monkey species (tufted capuchins, black-handed spider monkeys, and long-tailed macaques) on 16 cognitive ability measures. The differences between species pairs across measures are not generally strongly related to the degree to which the g factor loads on each subtest. Iteratively removing the subtests with the lowest coefficients of variance (CV), and recorrelating the species differences with subtest g-loadings was found to increase the association between the two. Across iterations, subtest pooled CV strongly and positively predicts the increase in the degree to which g-loadings are predictive of species difference in two comparisons, but is a weaker predictor in the comparison between tufted capuchins and black-handed spider monkeys. These associations were not related to phylogenetic distance but were very strongly related to species differences in the means of certain ecological factors. g-scores computed for each species on the basis of the three subtests with the highest CV values exhibited very-high magnitude (>.9) associations with species-level G-scores. G is simply the species-level equivalent of g, resulting from covariation among cognitive ability measures at the level of species differences. Finally, as with previous studies, subtests that show the greatest species differences seem to draw on executive functioning, and attention, suggesting that these may be a phylogenetically conserved source of g across many animal taxa. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Earliest evidence of primate captivity and translocation supports gift diplomacy between Teotihuacan and the Maya

A multimethod archaeometry study (zooarchaeological, isotopic, ancient DNA, paleobotanical, and radiocarbon dating) of a spider monkey sacrificed in the ceremonial center of Teotihuacan, Mexico (1 to 550 CE) is interpreted as a diplomatic gift exchange with neighboring Maya. Not only does this spider monkey provide the earliest known instance of primate translocation and captivity in Mesoamerica, it helps date incipient modes of interregional diplomacy between two major powers during Early Classic Mesoamerica: Teotihuacan and the Maya. Details of human-primate interaction include age at capture and transport (before ∼3 y of age), captive duration (over 2 y), anthropogenic diet (staple was maize, though secondary resources unique to anthropogenic diet including arrowroot and chili pepper were also found), context of sacrifice (tethered and associated with complete golden eagle and an array of other statecrafts), and general site context (including presence of Maya vessels and Maya-style murals). The timing of the spider monkey's sacrifice (250 to 300 CE) and its life history suggest a reconsideration of epigraphically attested militaristic involvement of Teotihuacan at certain Maya sites. We propose that a period of more multilateral and fluid ritual exchange with Maya dignitaries preceded the Teotihuacan state's eventual ascent to prominence.

A Hybrid Spider Monkey and Hierarchical Particle Swarm Optimization Approach for Intrusion Detection on Internet of Things

The Internet of Things (IoT) network integrates physical objects such as sensors, networks, and electronics with software to collect and exchange data. Physical objects with a unique IP address communicate with external entities over the internet to exchange data in the network. Due to a lack of security measures, these network entities are vulnerable to severe attacks. To address this, an efficient security mechanism for dealing with the threat and detecting attacks is necessary. The proposed hybrid optimization approach combines Spider Monkey Optimization (SMO) and Hierarchical Particle Swarm Optimization (HPSO) to handle the huge amount of intrusion data classification problems and improve detection accuracy by minimizing false alarm rates. After finding the best optimum values, the Random Forest Classifier (RFC) was used to classify attacks from the NSL-KDD and UNSW-NB 15 datasets. The SVM model obtained accuracy of 91.82%, DT of 98.99%, and RFC of 99.13%, and the proposed model obtained 99.175% for the NSL-KDD dataset. Similarly, SVM obtained accuracy of 85.88%, DT of 88.87%, RFC of 91.65%, and the proposed model obtained 99.18% for the UNSW NB-15 dataset. The proposed model achieved accuracy of 99.175% for the NSL-KDD dataset which is higher than the state-of-the-art techniques such as DNN of 97.72% and Ensemble Learning at 85.2%.

Mother-infant relationships and infant independence in wild Geoffroy's spider monkeys (Ateles geoffroyi)

We studied mother-infant relationships and infant independence in wild Geoffroy's spider monkeys (Ateles geoffroyi) during the first 3 years of infant life. We used 15-min focal sampling to collect data on mother-infant interactions and infant behavior in 12 mother-infant dyads in the Yucatan peninsula, Mexico. Data were analyzed using generalized linear mixed models. Newborns spent almost all their time in proximity and in contact with their mothers. The time infants spent within one-arm reach from the mother decreased with age, and the infant was primarily responsible for maintaining proximity. The time infants spent farther than 8 m from the mother, in independent locomotion, exploration, and proximity with group members other than the mother increased with age. We identified two developmental periods associated with critical milestones of infant independence: the first at 8 to 10 months when independent locomotion and exploration began, and the proportion of time in proximity with group members other than the mother increased and the second at 19 to 21 months when the mother's rejection started, maternal carrying ended and mother's help, in the form of bridging canopy gaps, peaked. Compared with other primate species of similar size, Ateles geoffroyi have an extended dependence period, which could be related to the cognitive and developmental challenges imposed by their socioecological characteristics. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Flexible use of contact calls in a species with high fission-fusion dynamics

The 'social complexity hypothesis' posits that complex social systems (which entail high uncertainty) require complex communicative systems (with high vocal flexibility). In species with fission-fusion dynamics, where the fluid composition of temporary subgroups increases the uncertainty with which group members must manage their social relationships, vocal communication must be particularly flexible. This study assessed whether contact call rates vary with caller and audience characteristics in free-living spider monkeys, as well as with fission and fusion events. Adult females and immature individuals called more when in small audience settings, while audience size did not influence adult males. Adults called more when in the presence of the opposite sex, whereas immatures vocalized more in subgroups composed only by females. Females also called more when with their mature sons. We found higher call rates in periods during which fission and fusion events took place than in periods with more stable compositions and when the composition after a fission or fusion event changed from one sex to two sexes. A flexible use of contact calls allows individuals to identify themselves when they join others, particularly if they are members of the opposite sex. This socio-spatial cohesion function reduces the uncertainty about subgroup composition. This article is part of the theme issue 'Cognition, communication and social bonds in primates'.

Variation in communicative complexity in relation to social structure and organization in non-human primates

Communicative complexity relates to social complexity, as individuals in more complex social systems either use more signals or more complex signals than individuals living in less complex ones. Taking the individual group member's perspective, here we examine communicative complexity in relation to social complexity, which arises from two components of social systems: social structure and social organization. We review the concepts of social relationships and social complexity and evaluate their implications for communicative and cognitive complexity using examples from primate species. We focus on spider monkeys (Ateles geoffroyi), as their social organization is characterized by flexibility in grouping dynamics and they use a variety of communicative signals. We conclude that no simple relationship exists among social complexity, communicative complexity and cognitive complexity, with social complexity not necessarily implying cognitive complexity, and communicative and cognitive complexity being independently linked to social complexity. To better understand the commonly implied link between social complexity and cognitive complexity it is crucial to recognize the complementary role of communicative complexity. A more elaborated communicative toolkit provides the needed flexibility to deal with dynamic and multifaceted social relationships and high variation in fission-fusion dynamics. This article is part of the theme issue 'Cognition, communication and social bonds in primates'.

Forest maturity has a stronger influence on the prevalence of spider monkeys than howler monkeys in an anthropogenically impacted rainforest landscape

The transformation and depletion of primary forest over the past few decades have placed almost half of the world’s primate species under the threat of extinction. Developing any successful conservation program for primates requires distribution and demography data, as well as an understanding of the relationships between these factors and their habitat. Between March and June 2010 and 2011 we collected data on the presence and demographic parameters of howler and spider monkeys by carrying out surveys, and validated our findings using local knowledge. We then examined the relationship between forest type and the presence of these primates at 54 sites in the northern area of the Selva Zoque Corridor, Mexico. We detected 86 spider monkey groups across 31 plots and censused 391 individuals (mean ± SD = 5.9 ± 3.0 individuals per sub-group, n = 67 sub-groups). We also detected 69 howler monkey groups across 30 plots and censused 117 individuals (mean ± SD = 5.3 ± 2.4 individuals per group, n = 22 groups). Howler monkey presence was not related to any specific vegetation type, while spider monkeys were present in areas with a higher percentage of tall forest (trees > 25 m high). Overall, spider monkeys were more prevalent than howler monkeys in our sampling sites and showed demographic characteristics similar to those in better protected areas, suggesting that the landscape features in the Uxpanapa Valley are suitable for their needs. Conversely, howler monkey presence was found to be more limited than in other regions, possibly due to the extended presence of spider monkeys.

Should I stay or should I go? How activity synchronization affects fission decisions

Group-living animals need to deal with conflicting interests to maintain cohesion. When the costs of doing so outweigh the benefits, the group may (temporarily) split into two or more subgroups. Conflicting interests can concern what activity to pursue or the direction of travel. Temporary group separation is a common feature in species with a high degree of fission-fusion dynamics. We investigated the role activity synchronization played in fission decisions in a spider monkey group living in the Otoch Ma'ax Yetel Kooh Nature Reserve, Yucatan, Mexico. For 21 months, we recorded every fission event occurring in the followed subgroup, as well as the subgroup activity. We classified the activity as 'synchronized' when at least 75% of subgroup members performed the same activity (resting, foraging, socializing or travelling); otherwise, we classified it as 'non-synchronized'. We found that fission events occurred more often when the activity was non-synchronized. In addition, when the activity was synchronized, fission events occurred more often when spider monkeys were travelling than when they were engaged in other subgroup activities. Our findings highlight the role of conflicting interests over the activity to pursue and travel direction in fission decisions.

Factors in forgetting in spider monkeys, Ateles geoffroyi

This essay discusses current problems and factors with memory testing in spider monkeys. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Forgetting curve in spider monkeys (Ateles geoffroyi): Effects of delay but not the amount of information

The forgetting curve is a phenomenon in which animals fail to retrieve information about an event as time passes. We tested this effect in spider monkeys (Ateles geoffroyi) in a task where they had to retrieve a reward hidden in a container after a delay. We combined different delays (0, 5, 10, 20, and 30 s) and different numbers of containers in which the reward could be hidden (2-6) and tested their effects on the accuracy in retrieving the reward. Our data suggest that the longer the delay, the more errors the spider monkeys made. However, a greater number of containers meant only marginally lower accuracy. An analysis of the errors showed that the spider monkeys used spatial information and showed a generalization of responses that depended on the delay; the longer the delay, the greater the generalization and the dispersion of errors. In a second experiment, we tested whether spider monkeys could use visual cues to increase their accuracy. We used the same task with an apparatus with 6 containers and 30 s of delay. Three colors were used as cues, with each color associated with 1 pair of containers. The data showed that the colors did not increase the accuracy of responses but reduced the generalization of the errors. The findings resembled previous findings supporting dynamic field theory, but more investigation is necessary to understand the brain areas and the neural dynamics of spider monkeys to explain and predict their behavior. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Energy-Efficient Cluster-Head Selection for Wireless Sensor Networks Using Sampling-Based Spider Monkey Optimization

Extending the lifetime and stability of wireless sensor networks (WSNs) through efficient energy consumption remains challenging. Though clustering has improved energy efficiency through cluster-head selection, its application is still complicated. In existing cluster-head selection methods, the locations where cluster-heads are desirable are first searched. Next, the nodes closest to these locations are selected as the cluster-heads. This location-based approach causes problems such as increased computation, poor selection accuracy, and the selection of duplicate nodes. To solve these problems, we propose the sampling-based spider monkey optimization (SMO) method. If the sampling population consists of nodes to select cluster-heads, the cluster-heads are selected among the nodes. Thus, the problems caused by different locations of nodes and cluster-heads are resolved. Consequently, we improve lifetime and stability of WSNs through sampling-based spider monkey optimization and energy-efficient cluster head selection (SSMOECHS). This study describes how the sampling method is used in basic SMO and how to select cluster-heads using sampling-based SMO. The experimental results are compared to similar protocols, namely low-energy adaptive clustering hierarchy centralized (LEACH-C), particle swarm optimization clustering protocol (PSO-C), and SMO based threshold-sensitive energy-efficient delay-aware routing protocol (SMOTECP), and the results are shown in both homogeneous and heterogeneous setups. In these setups, SSMOECHS improves network lifetime and stability periods by averages of 13.4%, 7.1%, 34.6%, and 1.8%, respectively.

Homosexual Behavior Between Male Spider Monkeys (Ateles geoffroyi)

Homosexual behavior is defined as genital contact or genital manipulation between same-sex individuals. In nonhuman primates, it may regulate social relationships by serving as a means of reconciliation, tension alleviation, or alliance formation. Grappling is a rare and complex behavior, which most frequently occurs between same-sex individuals of the genus Ateles and can include mutual manipulation of the genitalia. Here we report three cases of penile-anal intromission during grappling between wild male spider monkeys living in the natural protected area of Otoch Ma'ax Yetel Kooh, Mexico. In all the observed cases, the same adult male was the actor. To our knowledge, this is the first report of penile-anal intromission between males in any New World primate species.

Prevalence of neutralizing antibodies against West Nile virus (WNV) in monkeys (Ateles geoffroyi and Alouatta pigra) and crocodiles (Crocodylus acutus and C. acutus-C. moreletti hybrids) in Mexico

West Nile virus (WNV) is a mosquito-borne neurotropic viral pathogen maintained in an enzootic cycle between mosquitoes (vectors) and birds (natural hosts) with equids, humans, and other vertebrates acting as dead-end hosts. WNV activity in Mexico has been reported in several domestic and wild fauna and in humans, and the virus has been isolated from birds, mosquitoes, and humans. However, no serological studies have been conducted in monkeys, and only two in a limited number of crocodiles (Crocodylus moreletii). Here we present data on the prevalence of neutralizing antibodies against WNV in 53 healthy wild monkeys (49 Ateles geoffroyi and four Alouatta pigra), and 80 semi-captive healthy crocodiles (60 C. acutus and 20 C. acutus-C. moreletti hybrids) sampled during 2012. None of the monkey sera neutralized WNV, whereas 55% of the crocodile sera presented neutralizing antibodies against WNV. These results can contribute to the design of surveillance programmes in Mexico.

Tractography of the spider monkey (Ateles geoffroyi) corpus callosum using diffusion tensor magnetic resonance imaging

The objective of this research was to describe the organization, connectivity and microstructure of the corpus callosum of the spider monkey (Ateles geoffroyi). Non-invasive magnetic resonance imaging and diffusion-tensor imaging were obtained from three subjects using a 3T Philips scanner. We hypothesized that the arrangement of fibers in spider monkeys would be similar to that observed in other non-human primates. A repeated measure (n = 3) of fractional anisotropy values was obtained of each subject and for each callosal subdivision. Measurements of the diffusion properties of corpus callosum fibers exhibited a similar pattern to those reported in the literature for humans and chimpanzees. No statistical difference was reached when comparing this parameter between the different CC regions (p = 0.066). The highest fractional anisotropy values corresponded to regions projecting from the corpus callosum to the posterior cortical association areas, premotor and supplementary motor cortices. The lowest fractional anisotropy corresponded to projections to motor and sensory cortical areas. Analyses indicated that approximately 57% of the fibers projects to the frontal cortex and 43% to the post-central cortex. While this study had a small sample size, the results provided important information concerning the organization of the corpus callosum in spider monkeys.

Resistance to antibiotics of clinical relevance in the fecal microbiota of Mexican wildlife

There are a growing number of reports of antibiotic resistance (ATBR) in bacteria living in wildlife. This is a cause for concern as ATBR in wildlife represents a potential public health threat. However, little is known about the factors that might determine the presence, abundance and dispersion of ATBR bacteria in wildlife. Here, we used culture and molecular methods to assess ATBR in bacteria in fecal samples from howler monkeys (Alouatta palliata), spider monkeys (Ateles geoffroyi), tapirs (Tapirus bairdii) and felids (jaguars, Panthera onca; pumas, Puma concolor; jaguarundis, Puma yagouaroundi; and ocelots, Leopardus pardalis) living freely in two regions of the Mexican state of Veracruz under different degrees of human influence. Overall, our study shows that ATBR is commonplace in bacteria isolated from wildlife in southeast Mexico. Most of the resistances were towards old and naturally occurring antibiotics, but we also observed resistances of potential clinical significance. We found that proximity to humans positively affected the presence of ATBR and that ATBR was higher in terrestrial than arboreal species. We also found evidence suggesting different terrestrial and aerial routes for the transmission of ATBR between humans and wildlife. The prevalence and potential ATBR transfer mechanisms between humans and wildlife observed in this study highlight the need for further studies to identify the factors that might determine ATBR presence, abundance and distribution.

Seed source, seed traits, and frugivore habits: Implications for dispersal quality of two sympatric primates

• Premise of the study: Frugivore selection of fruits and treatment of seeds together with seed deposition site are crucial for the population dynamics of vertebrate-dispersed plants. However, frugivore species may influence dispersal quality differently even when feeding on the same fruit species and, while animals disperse some seeds, others simply fall beneath the parent plant.• Methods: In southern Mexico, we investigated to see if within-species seed traits (i.e., length, width, weight, and volume) and germination success differed according to seed source. For five tropical tree species we obtained ingested seeds from two sources, howler monkey (Alouatta pigra) and spider monkey (Ateles geoffroyi) feces; and noningested seeds from two sources, the ground and tree crowns (with predispersed seeds used as control).• Key results: A principal components' analysis showed that traits of seeds ingested by howler monkeys differed from other sources while seeds ingested by spider monkeys were similar to noningested seeds. Howlers consumed on average the larger seeds in Ampelocera hottlei, Brosimum lactescens, and Dialium guianense. Both primate species consumed the smaller seeds in Spondias mombin, while no seed trait differences among seed sources were found in Spondias radlkoferi. For all five tree species, germination rate was greatest for seeds ingested by howler monkeys.• Conclusions: For the studied plant species, seed ingestion by howler monkeys confers higher dispersal quality than ingestion by spider monkeys or nondispersal. Dispersal services of both primate species, however, are not redundant and may contribute to germination heterogeneity within plant populations in tropical forests.

Contagious deposition of seeds in spider monkeys' sleeping trees limits effective seed dispersal in fragmented landscapes

The repeated use of sleeping sites by frugivorous vertebrates promotes the deposition and aggregation of copious amounts of seeds in these sites. This spatially contagious pattern of seed deposition has key implications for seed dispersal, particularly because such patterns can persist through recruitment. Assessing the seed rain patterns in sleeping sites thus represents a fundamental step in understanding the spatial structure and regeneration of plant assemblages. We evaluated the seed rain produced by spider monkeys (Ateles geoffroyi) in latrines located beneath 60 sleeping trees in two continuous forest sites (CFS) and three forest fragments (FF) in the Lacandona rainforest, Mexico. We tested for differences among latrines, among sites, and between forest conditions in the abundance, diversity (α-, β- and, γ-components) and evenness of seed assemblages. We recorded 45,919 seeds ≥ 5 mm (in length) from 68 species. The abundance of seeds was 1.7 times higher in FF than in CFS, particularly because of the dominance of a few plant species. As a consequence, community evenness tended to be lower within FF. β-diversity of common and dominant species was two times greater among FF than between CFS. Although mean α-diversity per latrine did not differ among sites, the greater β-diversity among latrines in CFS increased γ-diversity in these sites, particularly when considering common and dominant species. Our results support the hypothesis that fruit scarcity in FF can 'force' spider monkeys to deplete the available fruit patches more intensively than in CFS. This feeding strategy can limit the effectiveness of spider monkeys as seed dispersers in FF, because (i) it can limit the number of seed dispersers visiting such fruit patches; (ii) it increases seed dispersal limitation; and (iii) it can contribute to the floristic homogenization (i.e., reduced β-diversity among latrines) in fragmented landscapes.

Olfactory sensitivity for six predator odorants in CD-1 mice, human subjects, and spider monkeys

Using a conditioning paradigm, we assessed the olfactory sensitivity of six CD-1 mice (Mus musculus) for six sulfur-containing odorants known to be components of the odors of natural predators of the mouse. With all six odorants, the mice discriminated concentrations <0.1 ppm (parts per million) from the solvent, and with five of the six odorants the best-scoring animals were even able to detect concentrations <1 ppt (parts per trillion). Four female spider monkeys (Ateles geoffroyi) and twelve human subjects (Homo sapiens) tested in parallel were found to detect the same six odorants at concentrations <0.01 ppm, and with four of the six odorants the best-scoring animals and subjects even detected concentrations <10 ppt. With all three species, the threshold values obtained here are generally lower than (or in the lower range of) those reported for other chemical classes tested previously, suggesting that sulfur-containing odorants may play a special role in olfaction. Across-species comparisons showed that the mice were significantly more sensitive than the human subjects and the spider monkeys with four of the six predator odorants. However, the human subjects were significantly more sensitive than the mice with the remaining two odorants. Human subjects and spider monkeys significantly differed in their sensitivity with only two of the six odorants. These comparisons lend further support to the notion that the number of functional olfactory receptor genes or the relative or absolute size of the olfactory bulbs are poor predictors of a species' olfactory sensitivity. Analysis of odor structure-activity relationships showed that in both mice and human subjects the type of alkyl rest attached to a thietane and the type of oxygen moiety attached to a thiol significantly affected olfactory sensitivity.

Functional redundancy and complementarities of seed dispersal by the last neotropical megafrugivores

BACKGROUND

Functional redundancy has been debated largely in ecology and conservation, yet we lack detailed empirical studies on the roles of functionally similar species in ecosystem function. Large bodied frugivores may disperse similar plant species and have strong impact on plant recruitment in tropical forests. The two largest frugivores in the neotropics, tapirs (Tapirus terrestris) and muriquis (Brachyteles arachnoides) are potential candidates for functional redundancy on seed dispersal effectiveness. Here we provide a comparison of the quantitative, qualitative and spatial effects on seed dispersal by these megafrugivores in a continuous Brazilian Atlantic forest.

METHODOLOGY/PRINCIPAL FINDINGS

We found a low overlap of plant species dispersed by both muriquis and tapirs. A group of 35 muriquis occupied an area of 850 ha and dispersed 5 times more plant species, and 13 times more seeds than 22 tapirs living in the same area. Muriquis dispersed 2.4 times more seeds in any random position than tapirs. This can be explained mainly because seed deposition by muriquis leaves less empty space than tapirs. However, tapirs are able to disperse larger seeds than muriquis and move them into sites not reached by primates, such as large forest gaps, open areas and fragments nearby. Based on published information we found 302 plant species that are dispersed by at least one of these megafrugivores in the Brazilian Atlantic forest.

CONCLUSIONS/SIGNIFICANCE

Our study showed that both megafrugivores play complementary rather than redundant roles as seed dispersers. Although tapirs disperse fewer seeds and species than muriquis, they disperse larger-seeded species and in places not used by primates. The selective extinction of these megafrugivores will change the spatial seed rain they generate and may have negative effects on the recruitment of several plant species, particularly those with large seeds that have muriquis and tapirs as the last living seed dispersers.

Sleeping sites and latrines of spider monkeys in continuous and fragmented rainforests: implications for seed dispersal and forest regeneration

Spider monkeys (Ateles geoffroyi) use sites composed of one or more trees for sleeping (sleeping sites and sleeping trees, respectively). Beneath these sites/trees they deposit copious amounts of dung in latrines. This behavior results in a clumped deposition pattern of seeds and nutrients that directly impacts the regeneration of tropical forests. Therefore, information on the density and spatial distribution of sleeping sites and latrines, and the characteristics (i.e., composition and structure) of sleeping trees are needed to improve our understanding of the ecological significance of spider monkeys in influencing forest composition. Moreover, since primate populations are increasingly forced to inhabit fragmented landscapes, it is important to assess if these characteristics differ between continuous and fragmented forests. We assessed this novel information from eight independent spider monkey communities in the Lacandona rainforest, Mexico: four continuous forest sites and four forest fragments. Both the density of sleeping sites and latrines did not differ between forest conditions. Latrines were uniformly distributed across sleeping sites, but the spatial distribution of sleeping sites within the areas was highly variable, being particularly clumped in forest fragments. In fact, the average inter-latrine distances were almost double in continuous forest than in fragments. Latrines were located beneath only a few tree species, and these trees were larger in diameter in continuous than fragmented forests. Because latrines may represent hotspots of seedling recruitment, our results have important ecological and conservation implications. The variation in the spatial distribution of sleeping sites across the forest indicates that spider monkeys likely create a complex seed deposition pattern in space and time. However, the use of a very few tree species for sleeping could contribute to the establishment of specific vegetation associations typical of the southeastern Mexican rainforest, such as Terminalia-Dialium, and Brosimum-Dialium.

Wood consumption by Geoffroyi's spider monkeys and its role in mineral supplementation

Wood consumption is a rare behavior in frugivorous primates; however, it can be necessary for nutritional balancing as it may provide macro and/or micronutrients that are scarce in the most frequently eaten items (fruits). We tested this hypothesis in six spider monkey (Ateles geoffroyi) communities inhabiting continuous and fragmented rainforests in Lacandona, Mexico. We investigated the importance of both live and decayed wood in the diet of the monkeys, and assessed if wood consumption is related to the nutritional composition of these items. In general, wood consumption was focused on trees of Licania platypus (Chrysobalanaceae) and Ficus spp. (Moraceae), and was similar in continuous forest and in fragments (mean ± SD; 24±20% vs 18±16% of total feeding time, respectively), but marginally higher in females than in males (16±14% vs 5±4%, respectively). Live and decayed wood were both poorer in lipids, proteins, total nonstructural carbohydrates, and total digestible nutrients compared to mature and immature fruits. Moreover, decayed wood of L. platypus showed consistently higher levels of sodium and calcium compared to fruits. In conclusion, our findings suggest that wood from decaying trees of L. platypus and Ficus spp. and young branch piths of L. platypus represents an important source of sodium and/or calcium in the diet of spider monkeys, particularly in the case of females. The protection of decaying trees within forests and fragments is therefore necessary for the appropriate management and conservation of this endangered primate species.

Neuroendocrine tumor in the lung of a captive black spider monkey (Ateles paniscus)

This paper describes a neuroendocrine (NE) tumor of the lung that was observed during the necropsy of a 14-year-old female black spider monkey (Ateles paniscus) with sudden death. Grossly, multifocal firm and coalescing nodular masses were observed in the lung. The histological examination showed the tumor to be an typical NE tumor with polygonal cells grouped in small solid aggregates, with regularly sized, spherical, centrally placed nuclei with modest, lightly granular cytoplasm suspended in a fibrovascular stroma. The immunohistochemical examination revealed the tumor to be positive for cytokeratin, chromogranin A and synaptophysin, and negative for CD56. To the best of our knowledge, this is the first report of NE tumor in the lung of the black spider monkey.

Rapid evolution of an X-linked microRNA cluster in primates

MicroRNAs (miRNAs) are a growing class of small RNAs (about 22 nt) that play crucial regulatory roles in the genome by targeting mRNAs for cleavage or translational repression. Most of the identified miRNAs are highly conserved among species, indicating strong functional constraint on miRNA evolution. However, nonconserved miRNAs may contribute to functional novelties during evolution. Recently, an X-linked miRNA cluster was reported with multiple copies in primates but not in rodents or dog. Here we sequenced and compared this miRNA cluster in major primate lineages including human, great ape, lesser ape, Old World monkey, and New World monkey. Our data indicate rapid evolution of this cluster in primates including frequent tandem duplications and nucleotide substitutions. In addition, lineage-specific substitutions were observed in human and chimpanzee, leading to the emergence of potential novel mature miRNAs. The expression analysis in rhesus monkeys revealed a strong correlation between miRNA expression changes and male sexual maturation, suggesting regulatory roles of this miRNA cluster in testis development and spermatogenesis. We propose that, like protein-coding genes, miRNA genes involved in male reproduction are subject to rapid adaptive changes that may contribute to functional novelties during evolution.

Application of assays for the diagnosis of toxoplasmosis in a colony of woolly monkeys (Lagothrix lagotricha)

Toxoplasma gondii infection is a common cause of morbidity and mortality in New World primate species. Clinical abnormalities associated with toxoplasmosis can be nonspecific, making it difficult to make a definitive antemortem diagnosis and initiate appropriate treatment. Toxoplasmosis in New World primates can have a rapid clinical course, which may lessen the diagnostic utility of antemortem tests. However, while there are a variety of T. gondii serum antibody tests and T. gondii polymerase chain reaction (PCR) assays available that are not species specific, these assays have not been comparatively applied to New World primate cases. Woolly monkeys (Lagothrix lagotricha), a species of New World primate, are highly susceptible to fatal toxoplasmosis. Archived serum samples from 15 living and deceased woolly monkeys housed at the Louisville Zoological Garden (Louisville, Kentucky) were tested for T. gondii antibodies by a commercially available latex agglutination kit, a commercially available indirect hemagglutination kit, and the modified agglutination test. In addition, aliquots of the sera were assayed for T. gondii DNA using a PCR assay. Both woolly monkeys that died of disseminated toxoplasmosis were positive in all four assays, indicating that each could be used to aid in the diagnosis of toxoplasmosis in this species. We suspect that these assays have applications to other species of New World primates.

Predation of wild spider monkeys at La Macarena, Colombia

The killing of an adult male spider monkey (Ateles belzebuth ) by a jaguar (Panthera onca) and a predation attempt by a puma (Felis concolor) on an adult female spider monkey have been observed at the CIEM (Centro de Investigaciones Ecológicas La Macarena), La Macarena, Colombia. These incidents occurred directly in front of an observer, even though it is said that predation under direct observation on any type of primate rarely occurs. On the basis of a review of the literature, and the observations reported here, we suggest that jaguars and pumas are likely to be the only significant potential predators on adult spider monkeys, probably because of their large body size.

Incorporating animal behavior into seed dispersal models: implications for seed shadows

Seed dispersal fundamentally influences plant population and community dynamics but is difficult to quantify directly. Consequently, models are frequently used to describe the seed shadow (the seed deposition pattern of a plant population). For vertebrate-dispersed plants, animal behavior is known to influence seed shadows but is poorly integrated in seed dispersal models. Here, we illustrate a modeling approach that incorporates animal behavior and develop a stochastic, spatially explicit simulation model that predicts the seed shadow for a primate-dispersed tree species (Virola calophylla, Myristicaceae) at the forest stand scale. The model was parameterized from field-collected data on fruit production and seed dispersal, behaviors and movement patterns of the key disperser, the spider monkey (Ateles paniscus), densities of dispersed and non-dispersed seeds, and direct estimates of seed dispersal distances. Our model demonstrated that the spatial scale of dispersal for this V. calophylla population was large, as spider monkeys routinely dispersed seeds >>100 m, a commonly used threshold for long-distance dispersal. The simulated seed shadow was heterogeneous, with high spatial variance in seed density resulting largely from behaviors and movement patterns of spider monkeys that aggregated seeds (dispersal at their sleeping sites) and that scattered seeds (dispersal during diurnal foraging and resting). The single-distribution dispersal kernels frequently used to model dispersal substantially underestimated this variance and poorly fit the simulated seed-dispersal curve, primarily because of its multimodality, and a mixture distribution always fit the simulated dispersal curve better. Both seed shadow heterogeneity and dispersal curve multimodality arose directly from these different dispersal processes generated by spider monkeys. Compared to models that did not account for disperser behavior, our modeling approach improved prediction of the seed shadow of this V. calophylla population. An important function of seed dispersal models is to use the seed shadows they predict to estimate components of plant demography, particularly seedling population dynamics and distributions. Our model demonstrated that improved seed shadow prediction for animal-dispersed plants can be accomplished by incorporating spatially explicit information on disperser behavior and movements, using scales large enough to capture routine long-distance dispersal, and using dispersal kernels, such as mixture distributions, that account for spatially aggregated dispersal.

Phosphatase activity in the limb bones of monkeys (Lagothrix humboldti) with hyperparathyroidism

The paper reports a study of the distribution of phosphatases in the femora of three specimens of Humboldt's woolly monkey (Lagothrix humboldti) suffering from chronic hyperparathyroidism. Bone structure ranged from the apparently normal to extreme osteitis fibrosa. Most marked changes were found in the distribution of alkaline phosphatase, which reached at least 10 times the normal levels in the bone of the second monkey in the series, dropping to levels still well above normal in that of the most severely affected animal. Very high concentrations were found in the deeper layers of hypertrophied growth cartilage and in the osteoblasts lining poorly calcified trabeculae, and high concentrations in the fibre bone of the third animal. Lack of mineralization and the development of osteitis fibrosa are thus associated with a marked increase in alkaline phosphatase activity. Osteoclasts reacted strongly for acid phosphatase but were negative for alkaline phosphatase. Acid phosphatase levels were comparatively high in fibre bone, but overall levels ranged from 1/20 to less than 1/100 those of alkaline phosphatase. Some slow staining for acid phosphatase probably represents residual activity at acid pH of the markedly increased alkaline phosphatase. There may be some association between a failure of mineralization and the presence of acid phosphatase in osteoclasts and osteoid. The aetiology of the monkeys' condition is discussed. It seems likely that the parathyroid hypertrophy and rachitic changes were caused by low blood calcium dependent on a low calcium diet and lack of vitamin D, in which the requirements of New World monkeys are reputedly high.

Effect of restraint on fasting gastric content of spider monkeys

The effect of restraint in a chair, compared to conditions permitting free movement, on the fasting gastric content was studied in spider monkeys during 3- and 24-hr experiments. In the 3-hr experiments, the volume and "free" and total acid concentrations were significantly reduced during restraint. The pepsin concentration was increased but not to a statistically significant level. In the 24-hr experiments, there was little change noted in volume and acid concentration throughout the study when the animals were restrained. In contrast the freemoving animals showed a greater volume during the period of daytime activity than when they were restrained, but exhibited a marked decrease in volume and acid concentration during the night. The pepsin concentration during the first 9 hr was significantly greater in the restraint experiments.

Twenty-four-hour collections of gastric content in spider monkeys

Hourly collections of fasting gastric content were made from six spider monkeys and two macaques with chronic gastric fistulae under conditions which allowed the animals free movement except during the collection period. A rise in pH was observed in 13 of 14 experiments after 6 pm while a return to a pH of 1–2 was seen in nine experiments between 7 and 8 AM the next morning. In two monkeys, each studied on three occasions, there was a significant decrease in volume and acid concentration coincident with the rise in pH. Pepsin concentrations did not change significantly. The electrolyte composition of samples with a pH of 7 or above and a chloride concentration of over 90 mEq/liter, was similar to that of the contents of a vagally-innervated pouch during the night except that the potassium concentration was twice as great in the fistula content. Pouch contents during feeding showed considerable acid secretion. The pH of the fasting gastric content of two macaques was greater than 3 over a 24-hr period.