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Primates have been studied extensively to understand their behavior and the mechanisms that allow information processing. However, when we closely analyze the species studied and the different projects and topics carried out with them, we found that some species have been highly studied, while others have only a few studies. These differences create a significant underrepresentation of some primate species that could be especially problematic when we use the available information to track the evolution and the diversification of behavior and the mechanisms for information processing. With this in mind, this review aims to show the state-of-the-art of different topics studied in Mexican primates and identify topics that could be studied in the future. The review also aims to demonstrate why working with native species is a path that many low- and middle-income countries like Mexico can follow to develop research programs in their homelands.

Parallel laser photogrammetry (PLP), which consists of attaching two or three parallel laser beams at a known inter‐beam distance to a camera, can be used to collect morphological measurements of organisms noninvasively. The lasers project onto the photo being taken, and because the inter‐beam distance is known, they act as a scale for image analysis programs like ImageJ. Traditionally, this method has been used to measure larger morphological traits (e.g., limb length, crown‐rump length) to serve as proxies for overall body size, whereas applications to smaller anatomical features remain limited. To that end, we used PLP to measure the testes of 18 free‐living mantled howler monkeys (Alouatta palliata) at La Selva Biological Station, Costa Rica. We tested whether this method could reliably measure this relatively small and globular morphology, and whether it could detect differences among individuals. We tested reliability in three ways: within‐photo (coefficient of variation [CV] = 4.7%), between‐photo (CV = 5.5%), and interobserver (intraclass correlation = 0.92). We found an average volume of 36.2 cm3 and a range of 16.4–54.4 cm3, indicating variation in testes size between individuals. Furthermore, these sizes are consistent with a previous study that collected measurements by hand, suggesting that PLP is a useful method for making noninvasive measurements of testes. Research Highlights: Testes measurements are a critical data type that can elucidate key questions related to sperm competition and endocrine disruption, and deriving the measurements noninvasively is a great benefit to conservation effortsWe collected and measured photos of 18 individual adult mantled howler monkeys (Alouatta palliata) from La Selva, Costa Rica via parallel laser photogrammetryWe used three tests of repeatability to provide evidence that parallel laser photogrammetry can be used to measure the testes of a large‐bodied nonhuman primate noninvasively while being precise and accurate [ABSTRACT FROM AUTHOR]

Anthropogenic activities have caused habitat fragmentation and loss, which are the main threats to primates. Because of this, ecological niche models have become a widely used tool to determine the potential habitat of species. These models rarely include biotic factors, although vegetation variables such as height and phenology, data derived from remote sensing, were integrated into this research. We developed a model to obtain the potential distribution of the primate A. palliata. Therefore, records of the presence of monkeys in the field were collected, and later data were obtained on the spectral index of vegetation and the height of the canopy, derived from remote sensing, bioclimatic variables were also used. Subsequently, these variables were analyzed using the Variance Inflation Factor to discriminate those with the highest correlation. Finally, we use a Maximum Entropy algorithm included in the Maxent software, together with the presence registration data, vegetation index, height, and bioclimatic data. The predicted distribution of A. palliata was strongly associated with canopy height, vegetation index (RVI), and warmest quarter precipitation (Bio18). The areas with the highest probability of the presence of A. palliata are strongly associated with cocoa agrosystems and certain spaces of natural vegetation such as mangroves. With the integration of the variables derived from remote sensing, the potential distribution model obtained an excellent evaluation, to predict cocoa agrosystems as available habitats of the howler monkey A. palliata, thus identifying areas with a high probability of the presence of this species of primate, and thus offer a tool to decision-makers, to plan future studies and then establish criteria for the creation of areas for the conservation of primates in Mexico. [ABSTRACT FROM AUTHOR]

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Most primate taxa are threatened by extinction and their populations are decreasing. The persistence of primates is thus conditional on conservation actions aimed at protecting them and their habitat. Here, we focus on the conservation of mantled howler monkeys (Alouatta palliata) in the Los Tuxtlas Biosphere Reserve, Mexico. Following the creation of the reserve in 1998, habitat availability and howler monkey abundance increased, suggesting that progress was being made in terms of the conservation of this species. Recent events, however, suggest otherwise, as mantled howler monkey habitat within the biosphere reserve is being disturbed by mining operations endorsed by the Mexican government. We report this case to raise awareness about the challenges for primate and habitat conservation in protected areas. Highlights: In 1998, a 155,000 ha natural reserve was established in southern Mexico that was due to protecting nonhuman primates, among other organisms.In May 2021, mining operations endorsed by the Mexican government started within the reserve near the habitat of mantled howler monkeys (Alouatta palliata), threatening several groups.This case study underscores the frailty of primate conservation in Mexico, even within protected areas. [ABSTRACT FROM AUTHOR]

Information contained in vocal signals can include a caller's individual identity, which can be potentially used for individual recognition. Individual recognition at a distance allows individuals to reduce the costs of aggressive interactions with neighbors by adjusting responses based on familiarity and/or past experiences. Howler monkey roars are long-distance vocal signals given mostly by males that function in group spacing. Although multiple aspects of howler monkey roaring behavior have been studied, detailed examinations of roar structure are scarce. With the goal to evaluate individuality in roars, we recorded eight, adult, male, black-and-gold howler monkeys (Alouatta caraya) in northeastern Argentina. Howler monkey roars are composed of respiratory cycles, in which an exhalatory and an inhalatory section can be distinguished. We selected 14–15 respiratory cycles per male, measuring one temporal and six spectrum-based parameters, and frequency from the first to the sixth formant. To assess individual distinctiveness in roars, we used stepwise Discriminant Function Analysis followed by leave-one out-cross validations for the complete respiratory cycle, for the exhalatory section and for the inhalatory section. We measured 119 respiratory cycles and the DFA correctly classified 59% of complete respiratory cycles, 56% of exhalatory sections, and 63% of inhalatory sections. These classifications were significantly higher than expected by chance. Our results show that black-and-gold howler monkey roars are individually distinctive, particularly the inhalatory section, and that formant frequencies and duration are key acoustic parameters to individualize roars. [ABSTRACT FROM AUTHOR]

Black and gold howler monkeys (Alouatta caraya) inhabit several eco-regions in South America with the highest population densities in riverine forests. Dam construction for electricity production represents a severe human alteration of ecosystems with consequences for primate conservation. To evaluate the possible loss of genetic diversity in A. caraya, we analysed and compared the genetic structure of the species across 22 study sites in Argentina (14), Paraguay (1), and Brazil (7). Four of these study sites (referred to as flooded) were sampled before dam-linked flooding which most likely caused a drastic decline or functional extinction of these populations. The genetic variability of 256 individuals was evaluated using 10 autosomal microsatellites (STRs) and 112 individuals by sequencing a fragment of 507 bp of mtDNA. DNA was extracted from tissue, blood, and faecal samples. Significantly higher values of genetic variability were observed for the flooded populations both in mtDNA and STRs. Population genetic structure showed a K = 1, 2, or 5 depending on the method, separating Argentinian and Paraguayan sites from Brazilian sites and, in the case of K = 5, two clusters were mostly represented by flooded populations. Isolation-by-distance analyses showed that geographic distances influence gene flow. Analytical methods, such as Pairwise Fst’s and Nei’s and regression model of Harpending and Ward, were concordant in detecting significant genetic structuring between flooded and remaining sites examined. Although some sites have very low sample sizes, these samples are of great importance since these sampling sites are currently flooded. Our results show that the study sites where dams were built had the greatest genetic diversity. As A. caraya is currently severely threatened by yellow fever outbreaks, the remaining populations may be more vulnerable to disease outbreaks due to impoverished genetic variability. Accordingly, it is essential to implement management actions to conserve the remaining populations. Our results underline the importance for Environmental Impact Assessments (EIA) to include data on the genetic structure of species in the affected sites prior to their alteration or destruction. These genetic data are also remarkably important for determining where to relocate specific individuals to help avoid biodiversity loss.

Objectives: Many group‐living primate species have evolved the capacity for some individuals to live alone for part of their lives, but this solitary life stage has rarely been the subject of focused research. The mantled howler monkey (Alouatta palliata) is a social primate species with bisexual dispersal that lives in mixed‐sex groups with low male‐to‐female sex ratios. Consequently, males often spend a long period of their lives as solitary individuals. This study compares the tree use, feeding, and long‐distance vocalization behavior of solitary and group‐living mantled howler monkey males living within a fragmented rainforest in Costa Rica, La Suerte Biological Research Station. Based on differences in competitive ability between solitary and group‐living males, we predicted that lone males would be found in significantly smaller feeding and resting trees, consume more low‐quality foods, and produce shorter howling bouts made at lower rates than group‐living males. Materials and methods: We collected data on tree use and feeding during 30‐min focal samples on male focal animals, recording data at 2‐min intervals. We measured the trees in which the monkeys fed and rested for two or more intervals, and recorded the plant parts consumed. We recorded howling behavior using all‐occurrences sampling. Results: Lone males used significantly smaller feeding and resting trees, consumed more low‐quality foods, and howled at lower rates but had longer howling bouts triggered by anthropogenic noise more than group‐living males. Discussion Our results demonstrate that lone males differ in their behavioral ecology compared to group‐living males, thus improving understanding of the solitary male life stage in primates. [ABSTRACT FROM AUTHOR]

Background Saliva contains a very complex mixture of proteins for defense against microbiological pathogens and for oral food perception. Howler monkeys are Neotropical primates that can consume a mostly leaf diet. They are well known to thrive in highly disturbed habitats where they may cope with a diversity of dietary challenges and infection risks. We aimed to describe the salivary proteome of howlers to contribute to better understanding of their physiology. Methods We analyzed the salivary proteins of wild black howler monkeys (Alouatta pigra), by SDS-PAGE-1-D and Nano LC-MS/MS and categorized them by their function involved in host defense and oral food perception. Results Our proteomic analysis identified 156 proteins in howler saliva including a number of host defense peptides that are the first line of defense in mammals, such as defensin, cathelicidin, dermcidin, and lactotransferrin, and proteins with anti-bacterial, anti-fungal, and anti-viral capacity, such as IgA, IgG, IgM, BPI, salivary heat shock 70 kDa protein, beta-2-microbulin, and protein S-100. We also identified key proteins necessary for taste perception, including salivary carbonic anhydrase VI, cystatin D, IgA, and fatty acid-binding protein. Proteins to detect astringent foods were identifying, including four members of cystatins (A, B, C and D), lactoperoxidase, and histidine-rich proteins. No chitinase and amylase were identified as would be expected because howlers do not eat insects and little starch. These findings provide basic information to future studies in oral biology, ingestive physiology, and physiological ecology of mammals and non-human primates.

Background: In 2007–2009, a major yellow fever virus (YFV) outbreak in Northern Argentina decimated the local howler monkey (Alouatta) population. Aims: To evaluate whether the surviving howler monkeys possess advantageous genetic variants inherited from monkeys alive prior to the YFV outbreak, we explored the relationship between Toll‐like receptor (TLR) 7 and TLR8 gene variation and YFV susceptibility. Methods: We used samples from Alouatta individuals in Misiones, Argentina alive before the YFV outbreak, individuals that died during the outbreak, and individuals that survived the outbreak and are alive today. We measured genetic divergence between Alouatta YFV exposure groups and evaluated Alouatta‐specific substitutions for functional consequences. Results: We did not find different allele frequencies in the post‐YFV exposure Alouatta group compared to the pre‐exposure group. We identified three nonsynonymous variants in TLR7 in Alouatta guariba clamitans. Two of these substitutions are under positive selection in functionally important regions of the gene. Discussion and Conclusions: Our results did not indicate that surviving howler monkey spossess advantageous genetic variants at greater frequency than those alive before the YFV outbreak. However, the positively selected unique coding differences in A. guariba clamitans are in the region important in pathogen detection which may affect YFV resistance. Morework is necessary to fully explore this hypothesis [ABSTRACT FROM AUTHOR]

Bertiella sp., a cestode known to infect a variety of hosts, including nonhuman primates and humans, was identified in Paraguay as early as 1895, but no systematic analysis of wild primates' gastrointestinal parasites has ever been carried out in Paraguay. Increased urbanization in southwest Paraguay has pushed the Paraguayan howler monkey (Alouatta caraya) into anthropogenic habitats, particularly in the city of Pilar (Ñeembucú department), giving rise to greater potential for zoonotic transmission between wild primates and humans. From July to December 2018, fecal samples were noninvasively collected from 48 howlers inside Pilar (urban environment), the Pilar Military Base (intermediate environment), and a ranch 27 km outside Pilar in the humid Chaco (natural environment) and analyzed for Bertiella eggs and proglottids using macro‐analysis and formol‐ether sedimentation. Howlers living in the urban environment had the highest rates of Bertiella infection (50% prevalence), with considerably lower infection rates in the intermediate environment (6.25% prevalence) and natural habitats (0% prevalence). A χ2 goodness‐of‐fit test indicated a significant difference between the three habitat types (p =.007, χ2 = 10.005, df = 2). While the habitat seems to impact the frequency of infection, Bertiella was not observed to select for other factors such as age or sex of the primate host. Here we identified a significant increase in the frequency of Bertiella infection in an urban environment, which can then be further transmitted to new hosts with more direct primate contact. Bertiella infection has already been documented in humans in Paraguay, all of which were associated with close primate contact. As howlers move into more urban habitats due to urbanization and habitat fragmentation, Bertiella could be introduced into this new ecosystem and has the potential to cause further infections in humans. Research Highlights: Infections of the cestode Bertiella sp. are found in significantly higher percentages in Paraguayan howler monkeys (Alouatta caraya) living in an urban habitat compared to their natural habitat.The chance of Bertiella infection was not affected by age or sex of the individual. [ABSTRACT FROM AUTHOR]

For wild primates, demography studies are increasingly recognized as necessary for assessing the viability of vulnerable populations experiencing rapid environmental change. In particular, anthropogenic changes such as habitat loss and fragmentation can cause ecological and behavioral changes in small, isolated populations, which may, over time, alter population density and demographic structure (age/sex classes and group composition) in fragment populations relative to continuous forest populations. We compared our study population of Endangered black howler monkeys (Alouatta pigra) in 34 forest fragments around Palenque National Park (PNP), Mexico (62 groups, 407 individuals), to the adjacent population in PNP, protected primary forest (21 groups, 134 individuals), and to previous research on black howlers in fragments in our study area (18 groups, 115 individuals). We used χ2 and Mann–Whitney U tests to address the questions: (a) what is the current black howler demographic population structure in unprotected forest fragments around PNP? (b) How does it compare to PNP's stable, continuous population? (c) How has it changed over time? Compared to the PNP population, the fragment populations showed higher density, a significantly lower proportion of multimale groups, and significantly fewer adult males per group. The population's age/sex structure in the fragmented landscape has been stable over the last 17 years, but differed in a higher proportion of multifemale groups, higher density, and higher patch occupancy in the present. In the context of conservation, some of our results may be positive as they indicate possible population growth over time. However, long‐term scarcity of adult males in fragments and associated effects on population demographic structure might be cause for concern, in that it may affect gene flow and genetic diversity. The scarcity of adult males might stem from males experiencing increased mortality while dispersing in the fragmented landscape, whereas females might be becoming more philopatric in fragments. Research Highlights: Fewer adult male black howler monkeys were present in the fragmented landscape compared to the population in the adjacent continuous forest in Palenque National Park (PNP).The population in forest fragments has maintained a largely stable composition over the last 17 years, although density and patch occupancy in the fragmented landscape have increased.Results indicate both possible population growth in the fragmented landscape, and differences in population demographic structure relative to PNP, with potential consequences for future population viability in forest fragments. [ABSTRACT FROM AUTHOR]

Sleep is the longest and most continuous behavioral phase in the 24 h cycle of mammals. However, selection of postures, substrates, and tree parts during sleep has not been adequately explored, as well as their evolutionary consequences. The present study investigates postural behavior, substrate, and tree part use during sleep in three howler species (A. palliata , A. macconnelli , and A. caraya) in Nicaragua, French Guiana, and Argentina. All three species were consistent in the use of a crouched ball-like sit-in posture on large, horizontal, unramified, or bifurcated substrates, and in avoiding the periphery of tree crowns. The regularities of these sleeping patterns are very likely functionally associated with protection from potential predators and extreme weather conditions, biomechanical stability, thermoregulation, and enhancement of the digestive process of hard-to-decompose plant material. [ABSTRACT FROM AUTHOR]

Objectives: Ecological similarity between species can lead to interspecific trophic competition. However, when ecologically similar species coexist, they may differ in foraging strategies and habitat use, which can lead to niche partitioning. As the body tissues of consumers contain a stable isotope signature that reflects the isotopic composition of their diet, stable isotope analysis is a useful tool to study feeding behavior. We measured the isotopic niche width, which is a proxy for trophic niche width, of mantled (Alouatta palliata) and black (A. pigra) howler monkeys. Specifically, studied populations in allopatry and sympatry to assess whether these species showed niche partitioning. Materials and Methods: Between 2008 and 2012, we collected hair samples from 200 subjects (113 black and 87 mantled howler monkeys) and used continuous flow isotope ratio mass spectrometry to estimate δ13C and δ15N. We described the isotopic niche width of each species in allopatry and sympatry with the Bayesian estimation of the standard ellipse areas. Results: In allopatry, isotopic niche width and isotopic variation were similar in both species. In sympatry, black howler monkeys had a significantly broader isotopic niche, which was mainly determined by high δ15N values, and included the majority of mantled howler monkeys' isotopic niche. The isotopic niche of mantled howler monkeys did not differ between sympatry and allopatry. Conclusions: The coexistence of these ecologically similar species may be linked to trophic niche adjustments by one species, although the particular features of such adjustments (e.g., dietary, spatial, or sensory partitioning) remain to be addressed. [ABSTRACT FROM AUTHOR]

Background. Saliva contains a very complex mixture of proteins for defense against microbiological pathogens and for oral food perception. Howler monkeys are Neotropical primates that can consume a mostly leaf diet. They are well known to thrive in highly disturbed habitats where they may cope with a diversity of dietary challenges and infection risks. We aimed to describe the salivary proteome of howlers to contribute to better understanding of their physiology. Methods. We analyzed the salivary proteins of wild black howler monkeys (Alouatta pigra), by SDS-PAGE-1-D and Nano LC-MS/MS and categorized them by their function involved in host defense and oral food perception. Results. Our proteomic analysis identified 156 proteins in howler saliva including a number of host defense peptides that are the first line of defense in mammals, such as defensin, cathelicidin, dermcidin, and lactotransferrin, and proteins with anti-bacterial, anti-fungal, and anti-viral capacity, such as IgA, IgG, IgM, BPI, salivary heat shock 70 kDa protein, beta-2-microbulin, and protein S-100. We also identified key proteins necessary for taste perception, including salivary carbonic anhydrase VI, cystatin D, IgA, and fatty acid-binding protein. Proteins to detect astringent foods were identifying, including four members of cystatins (A, B, C and D), lactoperoxidase, and histidinerich proteins. No chitinase and amylase were identified as would be expected because howlers do not eat insects and little starch. These findings provide basic information to future studies in oral biology, ingestive physiology, and physiological ecology of mammals and non-human primates. [ABSTRACT FROM AUTHOR]

To develop effective conservation and management actions, it is important to examine anthropogenic disturbance patterns and their impact on wildlife. We examined variation in the behavioral and physiological stress response of the Critically Endangered Mexican mantled howler monkeys Alouatta palliata mexicana in relation to two types of anthropogenic disturbance, habitat spatial patterns and presence of humans or their livestock (noise and presence nearby primates). We studied four groups (42 individuals) in two forest fragments at the Los Tuxtlas Biosphere Reserve for a total of 1100 observation hours, during which we recorded the howler monkeys' vocalizations, locomotion and vigilance. We additionally collected fecal samples to determine the concentrations of glucocorticoid metabolites (fGCM). Howler monkeys vocalized less and moved more when in more spatially disturbed locations and when exposed more time to nearby noise but spent less time in locomotion when humans were present. fGCM were only related to human presence, suggesting that habitat spatial patterns are less of a challenge than human presence. This may be related to the generally unpredictable nature of the latter. Although our study does not allow determining whether the behavioral and physiological responses of howler monkeys to disturbance are costly, from a conservation standpoint it may be more prudent to assume that they are and design strategies to mitigate them. In this sense, actions aimed at reducing anthropogenic noise could benefit the conservation of Mexican mantled howler monkeys. [ABSTRACT FROM AUTHOR]

Objective: Frequency‐dependent selection is expected to maintain infant sex ratios around parity over evolutionary time. However, over ecological time periods, infant sex ratios vary, and it has been proposed that this variation may reflect adaptive processes. In primates, there are consistent patterns of variation in infant sex ratios, although their adaptive significance remains contentious. In addition to design issues, contrasting results could have derived across primates from variation in the fitness benefits accrued through sons or daughters associated with the specific social, ecological, and demographic context of populations. Thus, different sex allocation tactics could occur within species over time and space. Methods: We reviewed the literature to describe variation in infant sex ratio in howler monkeys (genus Alouatta) and to examine whether such a variation could be associated with adaptive sex allocation. We found 26 studies that provided data for this review. These studies yielded 96 infant sex reports, corresponding to 1,477 sexed infants. Results: Infant sex ratio across howler monkey species tends to parity, but females produce more sons under high group densities and more daughters when rainfall increases. Discussion Based on these results, as well as on information on howler monkey dispersal patterns, demography, and within‐group genetic relatedness, we speculate that, depending on population growth stage, sex allocation is explained by (a) local resource enhancement, that is, more cooperative philopatric daughters are produced when populations are growing; and (b) local resource competition, that is, more dispersing sons are produced when populations are saturated. Thus, there is evidence suggestive of adaptive variation in infant sex ratios in howler monkeys. [ABSTRACT FROM AUTHOR]

Abstract Background Analyses of environmental correlates of the composition of gastrointestinal parasite communities in black howler monkeys (Alouatta pigra) have been hindered by inadequate calibration techniques of detection and quantification methods of the parasites. Here we calibrate samples and compare the likelihood of parasite detection using two flotation techniques, FLOTAC and Mini-FLOTAC, and compare flotation solution, preservation method and dilution ratio for egg detection and counts of the most common parasites (Controrchis spp. and Trypanoxyuris spp.) in howler monkeys. Results For samples preserved in 5% formalin, the Mini-FLOTAC technique was the best option for qualitative and quantitative copro-microscopic analysis. This technique displays an 83.3% and 100% detection of Controrchis spp. and Trypanoxyuris spp. infections, respectively. For the trematode Controrchis spp., more eggs per gram of feces (EPG) were recorded with the flotation solution (FS) #7 (zinc sulfate; specific gravity SG = 1.35) at 1:20 and 1:25 dilution than other methods. By contrast, for the nematode Trypanoxyuris spp., the best results were recorded with FS1 (sucrose and formaldehyde; SG = 1.20) at 1:10 dilution. Conclusions We recommend the Mini-FLOTAC technique for general use with parasite analysis on frugivore/folivores like the howler monkey, especially if many samples are analyzed. The technique has a high detection rate and the best EPG counts, allowing the qualitative and quantitative analysis of parasite load among the species or populations without the need for specialized equipment.

Multiple species of Phlebotominae are vectors of Leishmania (Protozoa: Trypanosomatidae), which causes visceral leishmaniasis (VL) and cutaneous leishmaniasis (CL). To describe the Phlebotominae (Diptera: Psychodidae) related to the environments of black and gold howler monkeys Alouatta caraya (Humbodlt, 1812) (Primates: Atelidae), potential vectors were sampled in different landscapes and vertical strata of sleeping trees. Phlebotomine captured between December 2011 and March 2012 (2365 individuals) belonged to eight species, of which Nyssomyia neivai (Pinto, 1926) (61.4%) and Migonemyia migonei (França, 1920) (18.73%) were the most abundant, and Ny. withmani was recorded for the first time in the Chaco province. In the 'peri‐domestic' landscape, the phlebotomine were mainly captured in henhouses (78.7%), whereas the tree canopy in 'rural' and 'wild' landscapes yielded 31.2% and 29.1% of the phlebotomine, respectively. A significant association between the type of landscape and the species of phlebotomine was observed by multivariate analysis. Lutzomyia longipalpis (Lutz & Neiva, 1912) and Mg. migonei were associated with 'peri‐domestic' landscape, and Ny. neivai was associated with the 'wild' landscape. The results of this prospective study suggest that the interaction between phlebotomine and A. caraya could be a key factor with respect to understanding the epidemiology of leishmaniasis. [ABSTRACT FROM AUTHOR]

Objectives: Platyrrhines constitute a diverse clade, with the modern Atelidae exhibiting the most variation in cranial and endocast morphology. The processes responsible for this diversification are not well understood. Here, we present a geometric morphometric study describing variation in cranial and endocranial shape of 14 species of Alouatta, Ateles, Brachyteles, and Lagothrix and two extinct taxa, Cartelles and Caipora. Methods: We examined cranial and endocranial shape variation among species using images reconstructed from CT scans and geometric morphometric techniques based on three‐dimensional landmarks and semilandmarks. Principal components analyses were used to explore variation, including the Procrustes shape coordinates, summing the logarithm of the Centroid Size, the common allometric component, and residual shape components. Results: Differences in endocranial shape are related to a relative increase or decrease in the volume of the neocortex region with respect to brainstem and cerebellum regions. The relative position of the brainstem varies from a posterior position in Alouatta to a more ventral position in Ateles. The shape of both the cranium and endocast of Caipora is within the observed variation of Brachyteles. Cartelles occupies the most differentiated position relative to the extant taxa, especially in regards to its endocranial shape. Conclusions: The pattern of variation in the extant species in endocranial shape is similar to the variation observed in previous cranial studies, with Alouatta as an outlier. The similarities between Caipora and Brachyteles were unexpected and intriguing given the frugivorous adaptations inferred from the fossil's dentition. Our study shows the importance of considering both extant and fossil species when studying diversification of complex traits. [ABSTRACT FROM AUTHOR]

The jaguar (Panthera onca) is widely distributed across a broad range of habitat types, where its feeding habits and habitat use patterns vary significantly. The jaguar and its main arboreal prey – the brown-throated sloth (Bradypus variegatus) and the red howler monkey (Alouatta juara) – are widespread in the Amazonian floodplain forests of the Mamirauá Reserve. These forest-dwelling species are the most common mammal species both in the continuous forest and the forest patches surrounded by a river matrix – the fluvial islands – of the Solimões and Japurá rivers. We used sign surveys along line-transects to assess the pattern of habitat occupancy by jaguars in Amazonian floodplain forests. Specifically, we (i) tested whether habitat occupancy by jaguars differs between river islands and continuous forest; and (ii) evaluated whether and how the local abundance of sloths and howler monkeys influence the probability of site occupancy by jaguars. We built an occupancy model and used Bayesian inference to reach these goals. The proportion of sites estimated to be used by jaguars was ψ = 0.75 (HPD95: 0.36–1.00), and it did not differ between islands and continuous forest. The abundance of both prey species had a direct influence on jaguar's habitat use, whereas the aquatic matrix seems to have a negligible effect on the use of islands by jaguars. We conclude that the isolation of the river islands within the aquatic matrix does not hamper jaguars to use them. We also conclude that prey search modulates jaguars' habitat occupancy patterns with both prey species having a similar effect. This finding is compatible with the previously reported importance of sloths to the diet of jaguars in the study region despite its lower abundance than howlers. Finally, we suggest that sign surveys are an alternative method to assess the pattern of jaguar habitat occupancy in floodplain forests. • Jaguars and its prey are widespread in Amazonian seasonally flooded forests. • Island occupancy by these species requires their ability to swim across the rivers. • Jaguar habitat occupancy was found to be similar in islands and continuous forest. • Prey search modulates jaguars' habitat occupancy patterns. [ABSTRACT FROM AUTHOR]

Background: Bifidobacterium genus are considered to be beneficial bacteria for their hosts; however, knowledge about the specific species that are part of the gut microbiome of howler monkeys is scarce. Polymerase chain reaction (PCR) is a useful technique for the identification of non‐cultivable or difficult to grow bacterial species. With the goal of detecting species of the genus Bifidobacterium in black howler monkeys, we used PCR on DNA derived from faecal samples. Methods: We collected and extracted DNA from 40 faecal samples. Using specific primers, we performed PCR and nested PCR to detect members of the Bifidobacterium genus and a subset of species: Bifidobacterium adolescentis, Bifidobacterium bifidum, Bifidobacterium infantis, Bifidobacterium longum and Bifidobacterium animalis subsp. animalis. Results: 97.5% (39/40) of the samples were positive for Bifidobacterium spp. We found B longum in 100% of the analysed samples. Conclusions: This is the first report of B longum in black howler monkey faeces. [ABSTRACT FROM AUTHOR]

Highlights • 26.47% of Allouata maintained in captivity in zoos in the state of São Paulo, Brazil, were positive for hemoplasmas. • Monocyte and lymphocite counts were higher in hemoplasma-positive howlers. • Platelets counts were decreased in hemoplasma-positive howlers. • Five different 16S rRNA hemoplasma genotypes are circulating in non-human primates in the world. • There is a separation between the 16S rRNA sequences of hemoplasmas that infect Sapajus and Allouata primates in Brazil. Abstract Mycoplasma spp. and Bartonella spp. are Gram-negative bacteria transmitted by arthropod vectors that infect red blood cells of several mammal species. This study investigated the occurrence and genetic diversity of hemoplasmas and Bartonella spp. in 68 howler monkeys kept in captivity in São Paulo, a southeastern state in Brazil. In addition, possible hematological, biochemical and electrophoretic changes of serum proteins associated with the occurrence of hemoplasmas and Bartonella spp. in captive primates were also investigated. The cPCR results showed that all sampled howler monkeys were negative for Bartonella spp. based on the gltA gene. The cPCR results indicated that 18 (26.47%) non-human primates (NHP) were positive for hemoplasmas based on the 16S rRNA gene. Monocyte and lymphocyte counts were higher in hemoplasma-positive howlers (P < 0.05). Platelet counts decreased in nonhuman primates (NHP) positive for hemoplasmas (P < 0.05). The results from the blood serum proteinogram and biochemistry analyses were not significantly different between NHPs positive and negative for hemotrophic mycoplasmas. Phylogenetic analysis using Bayesian Inference (BI) based on the 16S rRNA gene positioned the obtained sequences close to ' Candidatus Mycoplasma kahanei'. The analysis of sequence diversity of the 16S rRNA gene showed that 5 different genotypes are circulating in NHP in Brazil and in the world; besides, a clear separation between the sequences of hemoplasmas that infect NHP of the Sapajus and Alouatta genus in Brazil was found, probably corresponding to two different species. The pathogenic potential of this hemoplasma species in NHP should be further investigated. [ABSTRACT FROM AUTHOR]

Speciation occurs when populations diverge and become reproductively isolated from each other. Natural selection is commonly accepted to play a large role in this process, and it has been widely assumed that reproductive isolation often results as a by‐product of divergence driven by adaptation in allopatry. When such populations come into secondary contact, reinforcement can act to strengthen reproductive isolation, but the frequency and importance of this process are still unknown. Here, we explored genomic signatures of selection in allopatry and sympatry for loci associated with reproductive isolation using a natural primate hybrid zone. By analysing reduced‐representation sequencing data, we quantified admixture and population structure across a howler monkey hybrid zone and examined the relationship between locus‐specific differentiation and introgression. We detected extensive admixture that was mostly limited to the narrow contact zone. Loci with reduced introgression into the heterospecific genomic background (the pattern expected for loci associated with reproductive isolation due to selection against hybrids) were significantly more differentiated between allopatric parental populations than loci with neutral and increased introgression, supporting the hypothesis that reproductive isolation is a by‐product of divergence in allopatry. Further, loci with reduced introgression showed greater differentiation in sympatry than in allopatry, suggesting a role for reinforcement. Thus, our results reflect multiple forms of selection that have shaped reproductive isolation in this system. We conclude that reproductive isolation may have initially been driven by divergence in allopatry, but later reinforced by divergent selection in sympatry. [ABSTRACT FROM AUTHOR]

Rewilding has been an increasingly popular tool to restore plant–animal interactions and ecological processes impaired by defaunation. However, the reestablishment of such processes has seldom been assessed. We investigated the restoration of ecological interactions following the reintroduction of the brown howler monkey (Alouatta guariba) to a defaunated Atlantic forest site. We expected the reintroduction to restore plant–animal interactions and interactions between howlers and dung beetles, which promote secondary seed dispersal. We estimated the number of interactions expected to be restored by the reintroduction to provide the baseline interaction richness that could be restored. We followed the reintroduced howler monkeys twice a week for 24 months (337 hours total) to assess their diet. We used howler monkey dung in secondary seed dispersal experiments with 2484 seed mimics to estimate the removal rates by dung beetles and collected the beetles to assess community attributes. We compared the potential future contribution of howler monkeys and other frugivores to seed dispersal based on the seed sizes they disperse in other areas where they occur. In 2 years, howler monkeys consumed 60 animal‐dispersed plant species out of the 330 estimated. Twenty‐one dung beetle species were attracted to experimentally provided dung; most of them were tunnelers, nocturnal, and large‐sized (>10 mm). On average 30% (range 0–100%) of the large seed mimics (14 mm) were moved by dung beetles. About 91% of the species consumed by howlers (size range 0.3–34.3 mm) overlapped in seed size with those removed by dung beetles. In our study area, howler monkeys may consume more large‐seeded fruit species than most other frugivores, highlighting their potential to affect forest regeneration. Our results show reintroductions may effectively restore ecological links and enhance ecological processes. Article impact statement: Reintroduction effectively restores plant‐animal interactions and can reverse defaunation. [ABSTRACT FROM AUTHOR]

Interspecific hybridization allows the introgression or movement of alleles from one genome to another. While some genomic regions freely exchange alleles during hybridization, loci associated with reproductive isolation do not intermix. In many model organisms, the X chromosome displays limited introgression compared to autosomes owing to the presence of multiple loci associated with hybrid sterility or inviability (the "large X-effect"). Similarly, if hybrids are produced, the heterogametic sex is usually inviable or sterile, a pattern known as Haldane's rule. We analyzed the patterns of introgression of genetic markers located in the mitochondrial (control region) and nuclear (autosomal microsatellites and sex chromosome genes) genomes of two howler monkey species (Alouatta palliata and A. pigra) that form a natural hybrid zone in southern Mexico, to evaluate whether the large X-effect and Haldane's rule affect the outcomes of hybridization between these sister species. To identify the level of admixture of each individual in the hybrid zone (N = 254) we analyzed individuals sampled outside the hybrid zone (109 A. pigra and 39 A. palliata) to determine allele frequencies of parental species and estimated a hybrid index based on nuclear markers. We then performed a cline analysis using individuals in the hybrid zone to determine patterns of introgression for each locus. Our analyses show that although the hybrid zone is bimodal (with no known F1 s and few recent generation hybrids) and quite narrow, there has been extensive introgression in both directions, and there is a large array of admixed individuals in the hybrid zone. Mitochondrial and most autosomal markers showed bidirectional introgression, but some had biased introgression toward one species or the other. All markers on the sex chromosomes and a few autosomal markers showed highly restricted introgression. This pattern is consistent with the hypothesis that the sex chromosomes make a disproportionate contribution to reproductive isolation, and our results broaden the taxonomic representation of these patterns across animal taxa. [ABSTRACT FROM AUTHOR]

The Southern brown howler monkey, Alouatta guariba clamitans, is one of the largest Neotropical primates. The objective of this study was to describe the origin and antimeric distribution of brachial plexus nerves in A. g. clamitans and, thereby, to provide information for comparative anatomy and for anatomy applied to loco-regional anaesthetic blocking in primates. For this purpose, a macrodissection of 10 thoracic limbs of corpses that were collected from highways was performed, and the corpses were stored in 10% formaldehyde solution. The brachial plexus was essentially formed from the ventral spinal branches of segments C5 to T1, although in one specimen the contribution of C4 and in another specimen the contribution of T2 was registered. There was a grouping of ventral branches in cranial, medium and caudal trunks, and branches of C5 and C7 were the ones that mostly contributed to the origin of nerves from the plexus. Comparatively, the brachial plexus from A. g. clamitans reflected characteristics that are typical in the primate order, but also of mammal species that require versatility and precision in movements of the thoracic limbs. On the basis of that similarity, it is proposed that anatomic landmarks for anaesthetic block techniques used in other primate species may be successfully applied to A. g. clamitans. [ABSTRACT FROM AUTHOR]

Abstract: Background: The advent of non‐invasive methods provides a powerful alternative to stress studies as the use of stressful handling techniques is no longer needed. However, many factors influence hormone metabolism such as sex, diet, and metabolic rate. Thus, validation should be species‐ and matrix‐specific. Methods: To assess stress response in brown howler monkeys Alouatta clamitans, we adopted an ACTH challenge test and parallelism to provide physiological and laboratorial validation. Radioimmunoassay was used to measure fecal levels of corticosterone. Results and Conclusions: All challenged animals presented a peak in fecal glucocorticoids levels the day after the treatment, while control animals did not. There were no significant sex differences, but females with infants had higher levels of corticosterone. Corticosterone levels showed parallelism to the standard curve of the diagnostics kit. Collectively, the data suggest that the method was validated and is useful for monitoring stress, thereby helping in conservation programs both in captivity and in the wild. Transit time information may be coupled with travel distance in seed dispersal studies. [ABSTRACT FROM AUTHOR]

The genus Alouatta hosts species popularly known as red-handed howler, presenting wide geographic distribution and being found in several biomes. The objective is to describe the anatomy of the spinal cord of Alouatta belzebul specimens, focusing on the topography of the medullary cone, stressing the cervical and lumbar intumescences and cauda equina, to provide anatomical data and compare it with other species to assist in anesthetic and surgical procedures. Four animals were received for scientific research, post mortem, from the fauna rescue program of the Hydroelectric Plant of Belo Monte - Pará, and they were fixed in 10% formaldehyde solution. Structures such as the medullary cone, cervical and lumbar intumescence, and cauda equina were photographed (Sony a200-10.2 mpx). After thawing, we measured the specimens and observed a size of 80 to 82 cm from head to toe. After the skin and musculature were removed, it was observed that the spine of all specimens presented 7 cervical, 13 thoracic, 5 lumbar and 3 fused sacral vertebrae. The spinal cord was exposed after the removal of vertebral arches, it has 22 cm length in all animals, presenting the cervical intumescence between C3 and C6 vertebrae, with average of 2.2 cm and lumbar intumescence between T11 and T12 vertebrae, with average of 1.65 cm. The medullary cone is located between T12 and L1 vertebrae, with average of 1.5 cm, and the cauda equina between L1 and S3, with an average of 15 cm. This study has an important role as the basis for epidural anesthesia in the species. [ABSTRACT FROM AUTHOR]

Seed dispersal is a key process driving the structure, composition, and regeneration of tropical forests. Larger frugivores play a crucial role in community structuring by dispersing large seeds not dispersed by smaller frugivores. We assessed the hypothesis that brown howler monkeys (Alouatta guariba clamitans) provide seed dispersal services for a wide assemblage of plant species in both small and large Atlantic forest fragments. Although fruit availability often decreases in small fragments compared with large ones, we predicted that brown howlers are efficient seed dispersers in quantitative and qualitative terms in both forest types given their high dietary flexibility. After a 36-month study period and 2,962 sampling hours, we found that howlers swallowed and defecated intact the vast majority of seeds (96%-100%) they handled in all study sites. Overall, they defecated ca. 315,600 seeds belonging to 98 species distributed in eight growth forms. We estimated that each individual howler dispersed an average of 143 (SD = 49) seeds >2 mm per day or 52,052 (SD = 17,782) seeds per year. They dispersed seeds of 58% to 93% of the local assemblages of fleshy-fruit trees. In most cases, the richness and abundance of seed species dispersed was similar between small and large fragments. However, groups inhabiting small fragments tended to disperse a higher diversity of seeds from rarely consumed fruits than those living in large fragments. We conclude that brown howlers are legitimate seed dispersers for most fleshy-fruit species of the angiosperm assemblages of their habitats, and that they might favor the regeneration of Atlantic forest fragments with the plentiful amount of intact seeds that they disperse each year. [ABSTRACT FROM AUTHOR]

Abstract: Background: This study aimed at assessing the heart function of one neotropical primate (Alouatta guariba clamitans) kept in captivity using radiography, electrocardiogram (ECG) and Doppler echocardiography. Methods: Ten adult healthy howler monkeys (A. g. clamitans) were evaluated under general anaesthesia. Vertebral Heart Scores (VHS) were obtained from radiographic studies. Ejection fraction, shortening fraction of left ventricle, left atrial/aortic root ratio, ascending aortic diameter, peak velocity of pulmonary, mitral, tricuspid and aortic blood flow and other values were measured by Doppler echocardiography. Heart rate, mean electrical axis of QRS complex, P, Q, R, S, T amplitude, P, PR interval, QRS, QT interval duration and ST segment unbalancing were measured by ECG. Results and conclusions: Exam techniques were akin the ones used in humans. Doppler echocardiographic, radiographic, electrocardiographic and clinical parameters for howler monkey were described and correlated. The results have shown profiles of cardiovascular function and structure of A. g. clamitans. [ABSTRACT FROM AUTHOR]

Dietary tannins can affect protein digestion and absorption, be toxic, and influence food selection by being astringent and bitter tasting. Animals that usually ingest tannins may regularly secrete tannin‐binding salivary proteins (TBSPs) to counteract the negative effects of tannins or TBSPs production can be induced by a tannin‐rich diet. In the wild, many primates regularly eat a diet that contains tannin‐rich leaves and unripe fruit and it has been speculated that they have the physiological ability to cope with dietary tannins; however, details of their strategy remains unclear. Our research details the salivary protein composition of wild and zoo‐living black howler monkeys (Alouatta pigra) feeding on natural versus manufactured low‐tannin diets, and examines differences in TBSPs, mainly proline‐rich proteins (PRPs), to determine whether production of these proteins is dependent on the tannin content of their food. We measured the pH, flow rate, and concentration of total protein and trichloroacetic acid soluble proteins (an index of PRPs) in saliva. Howler monkeys produced slightly alkaline saliva that may aid in the binding interaction between tannin and salivary proteins. We used gel electrophoresis to describe the salivary protein profile and this analysis along with a tannin‐binding assay allowed us to detect several TBSPs in all individuals. We found no differences in the characteristics of saliva between wild and zoo‐living monkeys. Our results suggest that black howler monkeys always secrete TBSPs even when fed on foods low in tannins. This strategy of constantly using this salivary anti‐tannin defense enables them to obtain nutrients from plants that sometimes contain high levels of tannins and may help immediately to overcome the astringent sensation of their food allowing howler monkeys to eat tanniferous plants. [ABSTRACT FROM AUTHOR]

Range defensibility is defined as the ability of animals to efficiently move over an area to monitor and defend it. Therefore, range defensibility can help us understand the spatial structure of animal territoriality. We used howler monkeys (Alouatta spp.), a genus for which no agreement on the extent of their territoriality exists, to investigate the factors mediating range defensibility. We compared the defensibility index (D) across 63 groups of howler monkeys, representing 8 different species, based on a literature review. All species, except Alouatta palliata, were classified as potentially territorial according to D, although there was high variability within and among species. Group size had a positive effect on D, probably owing to the greater ability of groups to defend a territory as they become larger. Study area had a negative effect on D, perhaps suggesting that unlike small areas, large areas allow groups to have territories that do not require significant defense from neighbors. However, population density was the factor with the strongest effect on D, with greater monitoring of home ranges under high levels of competition. Our results suggest that howler monkeys are theoretically capable of maintaining a territory and suggest that animals can show a gradient in territoriality, which can be mediated by the competitive context in which it occurs. [ABSTRACT FROM AUTHOR]

Abstract: When sons and daughters impart different fitness benefits, mothers should bias investment according to offspring sex, in some cases modifying offspring sex ratios. Sex allocation in monotocous organisms is expected to be costlier than for polytocous species, as it imposes a greater loss of reproductive effort in terms of mating and fertilization. Here, we show that variation in glucocorticoid concentrations around the time of conception predicts infant sex in a monotocous anthropoid, the black howler monkey (Alouatta pigra), suggesting that sex allocation is linked to a hormonal mechanism that affects early embryonic development. Glucocorticoids signal environmental conditions, and in our study, their variation was positively related to factors affecting infant survival. These results offer insight into sex allocation strategies in monotocous organisms. [ABSTRACT FROM AUTHOR]

A lack of basic knowledge about the Endangered Caatinga howler monkey (Alouatta ululata) in Northeastern Brazil makes it difficult to design and implement effective conservation strategies. Traditional or Local Ecological Knowledge (LEK) has contributed to the development of conservation strategies for many species, including primates. Thus, we aimed to improve our understanding of the geographic range of Caatinga howler monkey, collect LEK on the species, and understand how people interact with these howlers to help future conservation efforts. We conducted semistructured interviews with members of local communities in two regions within the currently known distribution range of the species. We constructed maps based on the information currently available in the literature and on the data obtained through our interviews. Through LEK, we identified new areas of occurrence for Caatinga howler monkeys, increasing the species' range in a Northeastern direction in the state of Ceará. Gross domestic product (GDP) and population size were inversely related to the amount of knowledge that the local human population showed about the Caatinga howler monkeys, indicating that local wealth influences in the amount of LEK. Despite a positive attitude towards Caatinga howler monkeys in both regions (i.e. howlers were not killed in retaliation for cropfeeding and locals found their vocalizations pleasant), we identified poaching and medicinal uses of the species. Our data demonstrated that the range of Caatinga howler monkeys was larger than previously recorded and also that local knowledge was crucial for triangulating the species location. [ABSTRACT FROM AUTHOR]

Howler monkeys (genus Alouatta) display a distinctive cranial architecture characterized by airorhynchy (or retroflexion of the facial skeleton on the cranial base), a small braincase, and a posteriorly oriented foramen magnum. This configuration has been associated with distinct factors including a high folivory diet, locomotion, and the presence of a specialized vocal tract characterized by large hyoid bone. However, the morphological relationships between the facial and neurocranial blocks in Alouatta have been scarcely investigated. In this study we quantitatively analyzed the cranial shape variation in Alouatta seniculus, to evaluate possible influences and constraints in face and braincase associated with airorhynchy. We also considered the structural role of the pteric area within the cranial functional matrix. We applied landmark‐based analysis and multivariate statistics to 31 adult crania, computing shape analyses based on 3D coordinates registration as well as the analysis of the Euclidean distance matrix to investigate patterns of intraspecific morphological variability. Our results suggest that allometry is the main source of variation involved in shaping cranial morphology in howlers, influencing the degree of facial proportions and braincase flattening, and generating the main sexual differences. Larger individuals are characterized by a higher degree of airorhynchy, neurocranial flattening, and expansion of the zygomatic arch. Allometric variations influence the skull as a whole, without distinct patterns for face and braincase, which behave as an integrated morphological unit. A preliminary survey on the pteric pattern suggests that the morphology of this area may be the result of variations in the vertical growth rates between face and braincase. Future studies should be dedicated to the ontogenetic series and focus on airorhynchy in terms of differential growth among distinct cranial districts. [ABSTRACT FROM AUTHOR]

Studies on parasites infecting non-human primates are essential to better understand the potential threat to humans of zoonoses transmission, particularly under the current processes of pervasive land use change and biodiversity loss. The natural ecosystems in the Middle Magdalena river basin in Colombia have suffered a dramatic reduction and transformation into pastures and agroindustrial monocultures, threatening their biodiversity, and probably affecting the dynamics between parasites and their hosts, as well as altering the disease transmission cycles between wild populations and humans. This study evaluated seasonality, prevalence and richness of intestinal parasites in three species of neotropical primates: Cebus versicolor, Ateles hybridus and Alouatta seniculus, in a fragmented forest in the Middle Magdalena river valley, Colombia. One hundred and eighty five faecal samples were collected between 2010 and 2015. Direct faecal smears were performed with saline solution (0.85%) and iodine solution (1%), in order to identify larvae and eggs based on their morphology. A large proportion of the samples examined (72.9%) was positive for intestinal parasites; seven families of nematodes were identified: Trichuridae, Trichostrongylidae, Oxyuridae, Strongyloididae, Ancylostomatidae , Ascarididae and Gnathostomatidae, two of protozoans: Entamoebidae and Balantiididae, as well as some eggs of trematodes, cestodes and acanthocephalans. Additionally, DNA extraction and sequencing were conducted on 30 faecal samples in order to identify Giardia sp. and Blastocystis hominis , two parasite species also present in humans. Molecular testing for Giardia sp. was negative and Blastocystis hominis was identified in a single sample of Alouatta seniculus . No clear patterns were observed for prevalence of intestinal parasites according to the season; nonetheless, parasite species richness was higher during the dry season. This study builds on our current understanding of intestinal parasites infecting wild neotropical primates and provides novel information on the patterns of intestinal parasites in primate communities exposed to anthropogenic disturbance. [ABSTRACT FROM AUTHOR]

Background: Analyses of environmental correlates of the composition of gastrointestinal parasite communities in black howler monkeys (Alouatta pigra) have been hindered by inadequate calibration techniques of detection and quantification methods of the parasites. Here we calibrate samples and compare the likelihood of parasite detection using two flotation techniques, FLOTAC and Mini-FLOTAC, and compare flotation solution, preservation method and dilution ratio for egg detection and counts of the most common parasites (Controrchis spp. and Trypanoxyuris spp.) in howler monkeys. Results: For samples preserved in 5% formalin, the Mini-FLOTAC technique was the best option for qualitative and quantitative copro-microscopic analysis. This technique displays an 83.3% and 100% detection of Controrchis spp. and Trypanoxyuris spp. infections, respectively. For the trematode Controrchis spp., more eggs per gram of feces (EPG) were recorded with the flotation solution (FS) #7 (zinc sulfate; specific gravity SG = 1.35) at 1:20 and 1:25 dilution than other methods. By contrast, for the nematode Trypanoxyuris spp., the best results were recorded with FS1 (sucrose and formaldehyde; SG = 1.20) at 1:10 dilution. Conclusions: We recommend the Mini-FLOTAC technique for general use with parasite analysis on frugivore/ folivores like the howler monkey, especially if many samples are analyzed. The technique has a high detection rate and the best EPG counts, allowing the qualitative and quantitative analysis of parasite load among the species or populations without the need for specialized equipment. [ABSTRACT FROM AUTHOR]

Black-and-gold howler monkeys Alouatta caraya, are arboreal primates, inhabitants of Neotropical forests, highly susceptible to the yellow fever virus, considered early 'sentinels' of outbreaks, and thus, of major epidemiological importance. Currently, anthropogenic habitat loss and modifications threatens their survival. Habitat modification can prevent, reduce or change dispersal behavior, which, in turn, may influence patterns of gene flow. We explored past and contemporary levels of genetic diversity, elucidated genetic structure and identified its possible drivers, in ten populations (n = 138) located in the southernmost distribution range of the species in South America, in Argentina and Paraguay. Overall, genetic variability was moderate (ten microsatellites: 3.16 ± 0.18 alleles per locus, allelic richness of 2.93 ± 0.81, 0.443±0.025 unbiased expected heterozygosity; 22 haplotypes of 491-bp mitochondrial Control Region, haplotypic diversity of 0.930 ± 0.11, and nucleotide diversity of0.01± 0.007). Significant evidence of inbreeding was found in a population that was, later, decimated by yellow fever. Population-based gene flow measures (FST = 0.13; θST = 018), hierarchical analysis of molecular variance and Bayesian clustering methods revealed significant genetic structure, grouping individuals into four clusters. Shared haplotypes and lack of mitochondrial differentiation (non-significant θST) among some populations seem to support the hypothesis of historical dispersal via riparian forests. Current resistance analyses revealed a significant role of landscape features in modeling contemporary gene flow: continuous forest and riparian forests could promote genetic exchange, whereas disturbed forests or crop/grassland fields may restrict it. Estimates of effective population size allow anticipating that the studied populations will lose 75% of heterozygosity in less than 50 generations. Our findings suggest that anthropogenic modifications on native forests, increasingly ongoing in Northeastern Argentina, Southern Paraguay and Southeastern Brazil, might prevent the dispersal of howlers, leading to population isolation. To ensure long-term viability and maintain genetic connectivity of A. caraya remnant populations, we recommend preserving and restoring habitat continuity. To conserve the species genetic pool, as well, the four genetic clusters identified here should be considered separate Management Units and given high conservation priority. In light of our findings and considering complementary non-genetic information, we suggest upgrading the international conservation status of A. caraya to “Vulnerable”. [ABSTRACT FROM AUTHOR]

The article reports on scientists studying howler monkeys and mosquitoes in Brazilian forests to find clues to when and where the Yellow fever virus could resurge in Brazil. Yellow fever is endemic in much of Brazil, but in 2017, cases appeared in areas not considered at risk before, leaving the people of Brazil feeling edgy as well.

Hormones have a key role in energy allocation, so their study allows understanding individual metabolic strategies. Because different hormones convey different information on the responses of individuals to energetic demands, a simultaneous analysis of variation in multiple hormones may offer a more reliable picture of metabolic strategies than single hormone assessments. In this study we focused on determining which factors were related to variation in fecal glucocorticoid and thyroid hormone metabolites in wild mantled howler monkeys ( Alouatta palliata ). Over 12 months, we determined fecal glucocorticoid and thyroid hormone metabolite levels of 11 adults belonging to two groups, and examined the relationship between hormone metabolites and a variety of behavioral, physiological, and ecological factors (e.g., food intake, sex/reproductive state, activity, participation in agonistic interactions). We found that glucocorticoids were elevated in gestating and lactating females compared to males and cycling females, and were also higher when individuals were more active and participated in agonistic interactions. Thyroid hormone levels were also related to sex/reproductive state and activity, but were additionally positively related to fruit intake and negatively related to young leaf intake. Our study demonstrates that the non-invasive measurement of glucocorticoid and thyroid hormones of howler monkeys allows assessing different underlying physiological processes. By combining different biomarkers, which has seldom been done with wildlife, we could also parse the influence of psychological vs. metabolic challenges for individual energetic condition, which may be instrumental for deciding which factors should be accounted for when studying different hormone-behavior interactions. [ABSTRACT FROM AUTHOR]

For brown howler monkeys ( Alouatta guariba clamitans ), diploid chromosome numbers varying from 2n = 45 to 2n = 52, with XX/XY, X1 X1 X2 X2 /X1 X2 Y, and X1 X1 X2 X2 X3 X3 / X1 X2 X3 Y1 Y2 sex chromosome systems have been described by mitotic studies but still await confirmation by meiotic analyses. We analyzed 3 male individuals sampled in the wild (in the municipality of Santa Maria, RS, Brazil) as well as 1 male and 1 female individual in cap tivity at the São Braz breeding center. Peripheral blood samples and testicular biopsies were taken. We found different diploid numbers for both sexes in somatic cells, 2n = 45,X1 X2 X3 Y1 Y2 in males and 2n = 46,X1 X1 X2 X2 X3 X3 in females, with 4 metacentric (9–12), 7 submetacentric (1–6, 8), and 9 acrocentric autosomal chromosome pairs (13–20, 22). X1 and X2 were submetacentric chromosomes, while X3, Y1, and Y2 were acrocentric ones. Spermatocyte microspreads were examined for synaptonemal complexes. Pachytene spermatocyte analysis was done to verify the chromosome number and morphologies observed in mitotic karyotypes. Immunodetection was performed using anti-SMC3 and anti-CREST antibodies. The presence of a sex chromosome pentavalent X1 X2 X3 Y1 Y2 in the males was confirmed by C-banding in metaphase I and by immunodetection in prophase I by the clear identification of 5 centromeres. The G-banded karyotype corresponded to that previously described for A. g. clamitans in the south of Brazil (Curitiba, Parana State, and Blumenau, Santa Catarina State) and for the Misiones Province, Argentina. [ABSTRACT FROM AUTHOR]

Alouatta species utter the most powerful primate vocalizations in the Neotropics and are well-known for their loud and long-lasting male howling bouts. However, the diversity of acoustic structures used in these howling bouts, as well as in non-howling contexts, and the relative contribution of the different group members to the entire vocal repertoire, needed to be explored further. This report provides the first detailed description of the vocal repertoire of black howler monkeys ( Alouatta pigra), focusing on acoustic structures and contexts of emission of both loud and soft calls as well as on the contribution rate of males and females to the different call types. Three free-ranging social groups of black howler monkeys living in Palenque National Park, Mexico were monitored. We identified twelve acoustically discriminable call types, eight described previously and four described here for the first time. A few call types were systematically emitted either isolated or during howling bouts, but most of them could be heard in both calling contexts. Three call types were emitted only by females and two only by males. Adult males' call rates (for the seven shared call types) were higher than those of females but only when considering calls emitted within howling bouts. Our contextual analysis enabled us to divide call types into potential functional categories, according to their degree of contribution, to intra-group versus inter-group interactions and to neutral-positive versus negative situations. We then discussed how socio-ecological factors, notably sex differences in social behaviors, may explain the variability found in the vocal repertoire of this species and compared our findings with the literature on other primate species. [ABSTRACT FROM AUTHOR]