Biogeographical and floristic predictors of the presence and abundance of mantled howlers (Alouatta palliata mexicana) in rainforest fragments at Los Tuxtlas, Mexico

Effect of landscape attributes on the occurrence of the endangered golden-headed lion tamarin in southern Bahia, Brazil

The golden-headed lion tamarin (Leontopithecus chrysomelas) is an endangered primate that occurs exclusively in the Atlantic Forest of southern Bahia, Brazil. Its geographic range has been severely reduced by deforestation and its populations are restricted to a human-modified landscape consisting primarily of Atlantic forest fragments and shade cacao (Theobroma cacao) agroforestry, locally known as cabrucas. In the last 30 years, there has been a 42% reduction in the geographic range and a 60% reduction in the population size of L. chrysomelas, with only 8% of its habitat represented by protected areas. Thus, we investigated the occurrence of L. chrysomelas in forest fragments and cabrucas based on interviews and using playback census, and evaluated the influence of landscape attributes on its occurrence. The occurrence was measured using a Generalized Linear Model using a set of 12 predictor variables, including fragment size and elevation. L. chrysomelas inhabited 186 (38%) of the 495 forest fragments and cabrucas. Most inhabited habitat patches (n = 169, 91%) are in the eastern portion (ca. 70 km wide region from the Atlantic coast to inland) of its geographic range. The remaining (n = 17, 9%) are in the western portion of the distribution, between 70 and 150 km from the Atlantic coast. Our models indicate a higher occurrence of L. chrysomelas in the eastern portion of its geographic range, where the landscape exhibits lower land cover diversity, greater functional connectivity, lower altitudes (<400 m), and is primarily composed of forest fragments and cabrucas with a higher core percentage. In contrast, we observed a lower occurrence of L. chrysomelas in the western portion, where the landscape is more diverse and heterogeneous due to anthropogenic activities, such as agriculture and livestock. We urge the establishment of ecological corridors via reforestation of degraded areas in the western portion of the range. This increase in habitat availability and suitability in the west together with the protection of the forests and cabrucas in the east would increase our chances of saving L. chrysomelas from extinction.

One step forward, two steps backward: The frailty of howler monkey conservation in Los Tuxtlas, Mexico

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.

The influence of anthropogenic noise on the behavior of male mantled howler monkeys

Anthropogenic noise is increasingly disturbing natural soundscapes and affecting the physiology, behavior, and fitness of wildlife. However, our knowledge about the impact of anthropogenic noise on wild primates is scant. Here, we assess the effects of anthropogenic noise on the behavior of male mantled howler monkeys (Alouatta palliata). Specifically, we describe the types, rates, and sound pressure level (SPL) of anthropogenic noise that occurs in areas inhabited by mantled howler monkeys and determine if the behavioral responses of males to anthropogenic noise are influenced by noise attributes. For 1 year (1753 h), we characterized anthropogenic noise in the Los Tuxtlas Biosphere Reserve (Veracruz, Mexico) and studied the behavior of males belonging to five groups. Anthropogenic noise was common, diverse, and varied among areas in terms of rate, type, and SPL. Males did not display behavioral responses toward most (60%) anthropogenic noises, but were more likely to respond to certain noise types (e.g., aerial traffic) and toward noise with high SPL. Group identity influenced the likelihood of displaying behavioral responses to noise. The most common behavioral responses were vocalizations and vigilance. Males vocalized in response to noise with high SPL, although this relationship depended on group identity. The effect of the number of noises on vocalizations also varied among groups. Males were more likely to display vigilance toward high SPL and infrequent noise, but, again, these relationships varied among groups. In sum, anthropogenic noise is pervasive in areas inhabited by mantled howler monkeys and influences male behavior. Experience and frequency of exposure may modulate the behavioral responses of male mantled howler monkeys to noise and explain the group differences.

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.

The occurrence of the red-handed howler monkey (Alouatta belzebul) in amazonian savannas is related to forest patch area and density of flooded area palms

All Neotropical primates are arboreal and thus depend on forests for their survival. Arboreality puts many Neotropical primates at risk of extinction due to the high rates of deforestation in the tropics. We assessed the influence of vegetation structure and forest patch attributes on the occurrence of the threatened red-handed howler monkey (Alouatta belzebul) in an Amazonian savanna. Using a sample of 38 forest patches in a region of approximately 2000 km² in the state of Amapá, northern Brazil, we used logistic regression to find the best predictors of the occurrence of A. belzebul. We assessed patch area, patch isolation, the proportion of seasonally flooded forest in the patch, the density of flooded area palms, forest height, canopy cover, and diameter at breast height of trees. Patch area and palm density were the best predictors of the occurrence of A. belzebul in forest patches, both having a positive effect on the probability of occurrence. Our results indicate that areas of flooded forest in forest patches may be keystone habitats for A. belzebul living in Amazonian savannas. The observed effect of palm density on A. belzebul suggests that this variable is useful for planning conservation actions, including the selection of areas for protection and management strategies for areas inhabited by this primate.

Effects of variation in forest fragment habitat on black howler monkey demography in the unprotected landscape around Palenque National Park, Mexico

Habitat loss and fragmentation are leading threats to biodiversity today, and primates are particularly vulnerable to anthropogenic habitat disturbance. However, few studies have examined how differential effects of variation in forest fragment characteristics on males and females in a primate population may affect demography and population persistence. We quantified the effects of variation in forest fragment characteristics on the within-fragment demography of black howler monkeys (Alouatta pigra) in forest fragments around Palenque National Park, Mexico, and how these effects differed between adult males and females. We quantified forest loss in the landscape between 2000 and 2017, and used a redundancy analysis to examine the effects of 15 variables quantifying fragment dimensions, forest composition and physical structure, and isolation on fragment population size and density, the proportion of adult males and females in the fragment population, and the mean number of adult males and females per group in 34 fragments (N = 393 monkeys). We hypothesized that (i) population size is positively correlated with fragment area, while population density is negatively correlated, and (ii) the composition of fragment populations results from differential effects of fragment variables on adult males and females. Forest cover decreased by 23.3% from 2000 to 2017. Our results showed a significant effect of fragment variables on population demography in fragments, accounting for 0.69 of the variance in the demographic response variables. Population size increased with fragment area and connectivity, while density decreased. Larger, less isolated fragments with better connectivity, characteristics indicative of abundant secondary growth, and those with more diverse vegetation but lower Simpson’s evenness indices tended to have more adult females per group and a higher proportion of adult females in the population. In contrast, fragments that were largely similar in characteristics of forest composition and structure, but that were more isolated from nearby fragments, had more adult males per group and a higher proportion of adult males. These results may stem from black howler females preferentially remaining in natal groups and fragments when possible, and dispersing shorter distances when they disperse, while males may be more likely to disperse between fragments, traveling longer distances through the matrix to more isolated fragments. These differential effects on males and females have important conservation implications: if females are more abundant in larger, less isolated fragments, while males are more abundant in more isolated fragments, then to effectively conserve this population, both landscape connectivity and fragment areas should be maintained and increased.

Demographic population structure of black howler monkeys in fragmented and continuous forest in Chiapas, Mexico: Implications for conservation

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.

Regional context and dispersal mode drive the impact of landscape structure on seed dispersal

Land-use change modifies the spatial structure of tropical landscapes, shaping global biodiversity patterns. Yet, it remains unknown how key ecological processes, such as seed dispersal, can be affected by changes in landscape patterns, and whether such effects differ among regions with different climate and disturbance intensity. We assessed the effect of five landscape metrics (forest cover, matrix openness, forest edge density, forest fragmentation, and interpatch distance) on the seed rain recorded in two Mexican fragmented regions (20 forest sites per region): the more deforested, defaunated, and windy Los Tuxtlas rainforest (LTX), and the better-preserved Lacandona rainforest (LAC). We quantified the proportions of dispersed tree species and their seeds, separately evaluating wind- and animal-dispersed species. Our findings support the hypothesis that forest loss is more important than fragmentation per se, negatively impacting the seed rain in both regions. As expected, landscape patterns were comparatively more important for wind-dispersed seeds in LTX, probably because of stronger wind events in this region. Specifically, proportions of wind-dispersed seeds and species decreased with increasing edge density, suggesting that forest edges prevent dispersal of wind-dispersed species, which may occur if edges create physical barriers that limit wind flow. This pattern can also be caused by source limitation in landscapes with more forest edges, as tree mortality rates usually increase at forest edges. The wind-dispersed seed rain was also positively related to matrix openness, especially in LTX, where wind flow can be favored by the dominance of treeless anthropogenic matrices. Surprisingly, the proportion of animal-dispersed seeds in LTX was positively related to matrix openness and patch isolation, suggesting that seed dispersers in more deforested regions may be forced to concentrate in isolated patches and use the available habitat more intensively. Yet, as expected, patch isolation limited wind-dispersed seeds in LAC. Therefore, dispersal (and potentially regeneration) of wind-dispersed trees is favored in regions exposed to stronger wind events, especially in landscapes dominated by regularly shaped patches surrounded by open areas. Conversely, animal-dispersed seeds are primarily favored by increasing forest cover. Preventing forest loss is therefore critical to promote animal seed dispersal and forest recovery in human-modified rainforests.

Howler monkey tolerance to habitat shrinking: Lifetime warranty or death sentence?

Habitat loss and fragmentation are major threats to the conservation of nonhuman primates. Given that species differ in their responses to fragmented landscapes, identifying the factors that enable them to cope with altered environments or that cause their extirpation is critical to design conservation management strategies. Howler monkeys (Alouatta spp.) are good models for studying the strategies of tolerant arboreal taxa and how they cope with spatial restriction, because they live in habitats ranging from vast pristine forests to small disturbed fragments and orchards. While some aspects of their ecology and behavior are conserved, others vary in predictable ways in response to habitat shrinking and decreasing resource availability. We argue that the ability of individual howler monkeys to inhabit low-quality environments does not guarantee the long-term persistence of the small populations that live under these conditions. Their local extirpation explains why few forest fragments below a given area threshold are frequently inhabited in landscapes where recolonization and gene flow are compromised by long isolation distances or less permeable matrices. In sum, howlers' ability to cope with habitat restriction at the individual level in the short-term may mask the inevitable fate of isolated populations, thereby compromising the persistence of the species at a regional scale in the long-term if howlers' need for protection in large forests is undervalued.

Lemur species-specific metapopulation responses to habitat loss and fragmentation

Determining what factors affect species occurrence is vital to the study of primate biogeography. We investigated the metapopulation dynamics of a lemur community consisting of eight species (Avahi occidentalis, Propithecus coquereli, Microcebus murinus, Microcebus ravelobensis, Lepilemur edwardsi, Cheirogaleus medius, Eulemur mongoz, and Eulemur fulvus) within fragmented tropical dry deciduous forest habitat in Ankarafantsika National Park, Madagascar. We measured fragment size and isolation of 42 fragments of forest ranging in size from 0.23 to 117.7 ha adjacent to continuous forest. Between June and November 2011, we conducted 1218 surveys and observed six of eight lemur species (M. murinus, M. ravelobensis, C. medius, E. fulvus, P. coquereli, and L. edwardsi) in the 42 fragments. We applied among patch incidence function models (IFMs) with various measures of dispersal and a mainland-island IFM to lemur species occurrence, with the aim of answering the following questions: 1) Do lemur species in dry deciduous forest fragments form metapopulations? 2) What are the separate effects of area (extinction risk) and connectivity/isolation (colonization potential) within a lemur metapopulation? 3) Within simulated metapopulations over time, how do area and connectivity/isolation affect occurrence? and 4) What are the conservation implications of our findings? We found that M. murinus formed either a mainland-island or an among patch metapopulation, M. ravelobensis formed a mainland-island metapopulation, C. medius and E. fulvus formed among patch metapopulations, and neither P. coquereli or L. edwardsi formed a metapopulation. Metapopulation dynamics and simulations suggest that area was a more consistent positive factor determining lemur species occurrence than fragment isolation and is crucial to the maintenance of lemur populations within this fragmented landscape. Using a metapopulation approach to lemur biogeography is critical for understanding how lemur species respond to forest loss and fragmentation.

A demographic history of a population of howler monkeys (Alouatta palliata) living in a fragmented landscape in Mexico

Long-term field studies are critical for our understanding of animal life history and the processes driving changes in demography. Here, we present long-term demographic data for the northernmost population of mantled howler monkeys (Alouatta palliata) residing in a highly anthropogenically fragmented landscape in Los Tuxtlas, Mexico. We carried out 454 monthly group visits to 10 groups of mantled howler monkeys between 2000 and 2011. The population remained relatively stable over the 11-year study period, with an overall increase in the total number of individuals. Birth rates and inter-birth intervals were comparable to those of howler monkeys at non-fragmented sites, suggesting that living in a fragmented landscape did not affect the reproductive output of our study population. Moreover, despite the landscape, dispersal events were commonplace, including many secondary dispersals (individuals emigrating from groups that they had previously immigrated into). Finally, we found a marked effect of seasonality on the dynamics of our study population. In particular, the period of lowest temperatures and resource scarcity between November and March was associated with higher mortality and reproductive inhibition, while the period of resource abundance between April and May was associated with the majority of conceptions and weaning of offspring. This, in turn, could be influencing dispersal patterns in our study area, as male howler monkeys seem to time some of their immigrations into new groups to coincide with the start of the period of higher fertility, while females preferentially joined new groups several months before the onset of this period. These data have important implications for the conservation and management of howler monkeys in fragmented landscapes, as well as for our understanding of the effect of seasonality over howler monkey dispersal, reproduction and survival.

Howlers and marmosets in Pacatuba: an overcrowded existence in a semi-deciduous Atlantic forest fragment?

The Atlantic forest of Brazil is extremely fragmented. This fragmentation has had a toll on the mammal’s assemblages. Although different species are not equally susceptible to fragmentation, populations of some species have become locally extinct. Primate populations in these fragments are in decline or have gone locally extinct. However, there is a dearth of information on density of primates in the highly fragmented Atlantic forest of NE Brazil. We conducted a series of censuses to record primates and other mammals in the Pacatuba semi deciduous forest (~267 ha). Most of the midsized and large mammals disappeared, even fragment-tolerant species such as sloths and coatis are missing in the area. Currently, marmosets (

Integrating field and satellite data for spatially explicit inference on the density of threatened arboreal primates

Spatially explicit models of animal abundance are a critical tool to inform conservation planning and management. However, they require the availability of spatially diffuse environmental predictors of abundance, which may be challenging, especially in complex and heterogeneous habitats. This is particularly the case for tropical mammals, such as nonhuman primates, that depend on multi-layered and species-rich tree canopy coverage, which is usually measured through a limited sample of ground plots. We developed an approach that calibrates remote-sensing imagery to ground measurements of tree density to derive basal area, in turn used as a predictor of primate density based on published models. We applied generalized linear models (GLM) to relate 9.8-ha ground samples of tree basal area to various metrics extracted from Landsat 8 imagery. We tested the potential of this approach for spatial inference of animal density by comparing the density predictions for an endangered colobus monkey, to previous estimates from field transect counts, measured basal area, and other predictors of abundance. The best GLM had high accuracy and showed no significant difference between predicted and observed values of basal area. Our species distribution model yielded predicted primate densities that matched those based on field measurements. Results show the potential of using open-access and global remote-sensing data to derive an important predictor of animal abundance in tropical forests and in turn to make spatially explicit inference on animal density. This approach has important, inherent applications as it greatly magnifies the relevance of abundance modeling for informing conservation. This is especially true for threatened species living in heterogeneous habitats where spatial patterns of abundance, in relation to habitat and/or human disturbance factors, are often complex and, management decisions, such as improving forest protection, may need to be focused on priority areas.

Proximal and Distal Predictors of the Spider Monkey's Stress Levels in Fragmented Landscapes

The rapid loss, fragmentation and degradation of tropical forests threaten the survival of many animal species. However, the way in which these phenomena affect animal health has been poorly explored, thus limiting the design of appropriate conservation strategies. To address this, here we identified using linear mixed models the effect of proximal (diet, activity pattern, hunting and logging) and distal (sum of the basal areas of fruiting-tree species [SBAFS], landscape forest cover and degree of forest fragmentation) variables over fecal glucocorticoid metabolite (fGCM) levels-hormones associated with animal health and fitness-of six groups of spider monkeys (Ateles geoffroyi) inhabiting six landscapes with different spatial structures in Mexico. Proximal variables showed a stronger predictive power over fGCMs than distal. In this sense, increases in travel time, the occurrence of hunting, and reductions in rest time and fruit consumption resulted in higher fGCM levels. Regarding distal variables, increases in SBAFS were negatively related to fGCM levels, thus suggesting that food scarcity increases stress hormone levels. Nevertheless, contrary to theoretical expectations, spider monkeys living in smaller tracts of forest spent less time travelling, but the same time feeding on fruit as those in more forested areas. The lower net energy return associated with this combination of factors would explain why, contrary to theoretical expectations, increased forest cover was associated with increased levels of fGCMs in these groups. Our study shows that, at least in the short term, spider monkeys in fragmented landscapes do not always present higher levels of stress hormones compared to those inhabiting continuous forest, and the importance of preserving fruit sources and controlling hunting for reducing the levels of stress hormones in free ranging spider monkeys.

Nonvolant mammalian populations in primary and secondary Central American rainforests as revealed by transect surveys

Secondary forests are now prominent features in Neotropical landscapes, yet little is known about their conservation value for nonvolant mammalian communities. We performed a 20-month study using transect walks to survey the nonvolant mammal fauna in primary and secondary forests at La Selva Biological Station in the Caribbean lowlands of northeastern Costa Rica. We found that secondary forests can hold complex mammalian communities and no species exhibited habitat preferences between primary and secondary forests. With few exceptions, behavioral and group dynamic characteristics of mammal species were similar between forest types. Our research allows us to address methodological questions and assess the effectiveness of transect sampling. Monthly detection rates vary widely by species and likely reflect short-term changes in behavior rather than population fluctuations. Air temperature and rainfall are the factors most associated with monthly detection rates for various species. Small-scale areas of higher and lower use are evident for several species. Neither time of morning for surveys nor number of observers per trail affects detection rate. We report current abundances for the most commonly observed species and note generally lower densities in the Caribbean lowlands than elsewhere in the Neotropics. This research highlights that in less seasonal, evergreen forests climatic factors can still affect mammalian behavior. Overall, we find that secondary forests are of high conservation value and that transect walks are an effective methodology to sample many nonvolant mammal species, and we present recommendations on how to sample properly to conduct rigorous and long-term studies.

Los bosques secundarios son mucho más comunes en el neotrópico, pero poco se sabe sobre su importancia en la conservación de comunidades de mamíferos no voladores. Durante 20 meses llevamos a cabo un estudio usando líneas de transectos para investigar la fauna de mamíferos no voladores en bosques primarios y secundarios en la Estación Biológica La Selva en las tierras bajas caribeñas al noreste de Costa Rica. Pudimos constatar que los bosques secundarios pueden albergarcomplejas comunidades de mamíferos y ninguna especie exhibe preferencias de hábitat entre bosque primario y secundario. Con pocas excepciones, las características dinámicas de grupo y comportamiento de especies de mamíferos fueron similares entre los dos tipos de bosque. Nuestra investigación nos permite abordar cuestiones metodológicas y evaluar la eficacia del muestreo con transectos. Las tasas mensuales de detección varían de acuerdo a la especie y probablemente reflejan cambios a corto plazo en las fluctuaciones del comportamiento en vez de la población. La temperatura del aire y la precipitación son los factores más asociados con las tasas mensuales de detección de distintas especies. Encontramos que varias especies muestran diferentes incidencias de uso en zonas pequeñas. Ni la hora de la mañana, ni el número de observadores en las encuestas por transecto afectan la tasa de detección. Presentamos la abundancia actual de las especies más comúnmente observadas y notamos en general bajas densidades en las tierras bajas del Caribe más que en otras partes del neotrópico. Esta investigación resalta que en los bosques menos estacionales, factores climáticos aún pueden afectar el comportamiento de mamíferos. En general, encontramos que los bosques secundarios son de alto valor para la conservación y que los muestreos en transectos son una metodología eficaz para estudiar muchas especies de mamíferos no voladores y presentamos recomendaciones sobre cómo llevar a cabo muestreos adecuados para realizar estudios rigurosos a largo plazo.

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.

Where to nest? Ecological determinants of chimpanzee nest abundance and distribution at the habitat and tree species scale

Conversion of forests to anthropogenic land-uses increasingly subjects chimpanzee populations to habitat changes and concomitant alterations in the plant resources available to them for nesting and feeding. Based on nest count surveys conducted during the dry season, we investigated nest tree species selection and the effect of vegetation attributes on nest abundance of the western chimpanzee, Pan troglodytes verus, at Lagoas de Cufada Natural Park (LCNP), Guinea-Bissau, a forest-savannah mosaic widely disturbed by humans. Further, we assessed patterns of nest height distribution to determine support for the anti-predator hypothesis. A zero-altered generalized linear mixed model showed that nest abundance was negatively related to floristic diversity (exponential form of the Shannon index) and positively with the availability of smaller-sized trees, reflecting characteristics of dense-canopy forest. A positive correlation between nest abundance and floristic richness (number of plant species) and composition indicated that species-rich open habitats are also important in nest site selection. Restricting this analysis to feeding trees, nest abundance was again positively associated with the availability of smaller-sized trees, further supporting the preference for nesting in food tree species from dense forest. Nest tree species selection was non-random, and oil palms were used at a much lower proportion (10%) than previously reported from other study sites in forest-savannah mosaics. While this study suggests that human disturbance may underlie the exclusive arboreal nesting at LCNP, better quantitative data are needed to determine to what extent the construction of elevated nests is in fact a response to predators able to climb trees. Given the importance of LCNP as refuge for Pan t. verus our findings can improve conservation decisions for the management of this important umbrella species as well as its remaining suitable habitats.

Behavioral and physiological responses to subgroup size and number of people in howler monkeys inhabiting a forest fragment used for nature-based tourism

Animals' responses to potentially threatening factors can provide important information for their conservation. Group size and human presence are potentially threatening factors to primates inhabiting small reserves used for recreation. We tested these hypotheses by evaluating behavioral and physiological responses in two groups of mantled howler monkeys (Alouatta palliata mexicana) at the "Centro Ecológico y Recreativo El Zapotal", a recreational forest reserve and zoo located in the Mexican state of Chiapas. Both groups presented fission-fusion dynamics, splitting into foraging subgroups which varied in size among, but not within days. Neither subgroup size nor number of people had an effect on fecal cortisol. Out of 16 behavioral response variables tested, the studied factors had effects on six: four were affected by subgroup size and two were affected by number of people. With increasing subgroup size, monkeys increased daily path lengths, rested less, increased foraging effort, and used more plant individuals for feeding. As the number of people increased, monkeys spent more time in lower-quality habitat, and less time engaged in social interactions. Although fecal cortisol levels were not affected by the factors studied, one of the monkey groups had almost twice the level of cortisol compared to the other group. The group with higher cortisol levels also spent significantly more time in the lower-quality habitat, compared to the other group. Our results suggest that particular behavioral adjustments might allow howler monkeys at El Zapotal to avoid physiological stress due to subgroup size and number of people. However, the fact that one of the monkey groups is showing increased cortisol levels may be interpreted as a warning sign, indicating that an adjustment threshold is being reached, at least for part of the howler monkey population in this forest fragment.

The effect of forest fragment characteristics on abundance of Colobus vellerosus in the forest-savanna transition zone of Ghana

We explore the factors influencing the abundance of Colobus vellerosus in 11 forest fragments [Boabeng-Fiema Monkey Sanctuary and 9 surrounding forest fragments (range: 3.2-190 ha)] in the forest-savanna transition zone of Ghana. We used a 'complete' count for the colobus census in the fragments. We determined the fragment sizes using geographic information system methods and assessed forest fragment quality (tree species richness). Colobus individuals were absent from 4 forest fragments but present in 7 (densities of 0.13/ha-1.63/ha). We modelled colobus density using Poisson regression and selected models based on corrected Akaike information criterion model weights. Fragment size and tree species richness in the fragments were positively associated with colobus density, whereas isolation distance of the forest fragments (range: 20-5,632 m) was negatively associated with colobus density. Our analysis suggests that the isolation distance between the fragments and Boabeng does impede colobus movement. As the colobus populations in Boabeng and Fiema increase, some of the unoccupied fragments may become more attractive to dispersing monkeys. Management measures that aim at increasing tree species richness within fragments, while maintaining some large trees between fragments, might help to increase the occupancy of some of the fragments that currently have no permanent colobus groups.

Parasitic infections of three Mexican howler monkey groups (Alouatta palliata mexicana) living in forest fragments in Mexico

In order to better understand how patterns of parasitism in howler monkeys are affected by forest fragmentation, we carried out a 1 year survey of gastrointestinal parasites in fecal samples from three groups of Mexican howler monkeys inhabiting different forest fragments in the Los Tuxtlas Biosphere Reserve, Mexico. The study groups were chosen because the conditions in which they lived suggested a potentially negative gradient for parasite richness and a positive gradient for levels of parasitism. We report for the first time the presence of Entamoeba coli in Alouatta palliata mexicana and of hookworms (Family Ancylostomidae) in A. palliata. A reduction in home range size and an increase in disturbance was associated with a loss of parasite richness, which in general was high. Parasite prevalence and the proportion of contaminated samples in which each parasite taxon was present was also high in general and there were no differences between groups. A factor related to the generally high levels of parasitism in our study groups could be the high humidity in the study area, because this favors the survival of parasitic free forms and increases the chances of infection. This would also account for the tendency towards higher levels of parasitism observed in the rainy season. Finally we did not find a pattern relating sex and parasitism.

Effects of habitat fragmentation and disturbance on howler monkeys: a review

We examined the literature on the effects of habitat fragmentation and disturbance on howler monkeys (genus Alouatta) to (1) identify different threats that may affect howlers in fragmented landscapes; (2) review specific predictions developed in fragmentation theory and (3) identify the empirical evidence supporting these predictions. Although howlers are known for their ability to persist in both conserved and disturbed conditions, we found evidence that they are negatively affected by high levels of habitat loss, fragmentation and degradation. Patch size appears to be the main factor constraining populations in fragmented habitats, probably because patch size is positively related to food availability, and negatively related to anthropogenic pressures, physiological stress and parasite loads. Patch isolation is not a strong predictor of either patch occupancy or population size in howlers, a result that may be related to the ability of howlers to move among forest patches. Thus, we propose that it is probable that habitat loss has larger consistent negative effects on howler populations than habitat fragmentation per se. In general, food availability decreases with patch size, not only due to habitat loss, but also because the density of big trees, plant species richness and howlers' home range size are lower in smaller patches, where howlers' population densities are commonly higher. However, it is unclear which vegetation attributes have the biggest influence on howler populations. Similarly, our knowledge is still limited concerning the effects of postfragmentation threats (e.g. hunting and logging) on howlers living in forest patches, and how several endogenous threats (e.g. genetic diversity, physiological stress, and parasitism) affect the distribution, population structure and persistence of howlers. More long-term studies with comparable methods are necessary to quantify some of the patterns discussed in this review, and determine through meta-analyses whether there are significant inter-specific differences in species' responses to habitat loss and fragmentation.

Differences in diet and activity pattern between two groups of Alouatta palliata associated with the availability of big trees and fruit of top food taxa

The threat that forest fragmentation and habitat loss presents for several Alouatta taxa requires us to determine the key elements that may promote the persistence of howler monkeys in forest fragments and to evaluate how changes in the availability of these elements may affect their future conservation prospects. In this study we analyzed the relationship between the availability of both big trees of top food taxa (BTTFT) (diameter at breast height>60) and fruit of top food taxa (FrTFT) in the home ranges of two groups of Alouatta palliata mexicana occupying different forest fragments in Los Tuxtlas, Mexico, and their diet and activity pattern. Both study groups preferred big trees for feeding and the group with lower availability of BTTFT in their home range fed from more, smaller food sources. Furthermore, both study groups also increased the number of food sources when their consumption of fruit decreased, and the group with lower availability of FrTFT in their home range fed from more food sources. The increase in the number of food sources used under such conditions, in turn, set up a process of higher foraging effort and lower rest. In summary, our results support other studies that suggest that the availability of big trees and fruit may be two important elements influencing the persistence of howler monkeys in forest fragments.

Diet of spider monkeys (Ateles geoffroyi) in Mesoamerica: current knowledge and future directions

Here we review all published articles and book chapters, as well as unpublished theses and data of Ateles geoffroyi diet to (1) summarize the literature; (2) synthesize general feeding patterns; (3) document plant taxonomic similarity in diet across study sites; and (4) suggest directions for future research and conservation priorities. We found 22 samples from five countries: Mexico, Guatemala, El Salvador, Costa Rica and Panama. Tropical wet forest is the most studied habitat (N=13 samples), followed by tropical dry forest (6) and tropical moist forest (3). Most samples have been carried out in large protected forests. In spite of showing an overall high dietetic diversity (364 species, 76 families), A. geoffroyi concentrated the majority of feeding time on a few species in the families Moraceae and Fabaceae. At all study sites fruits were the most common food item in the diet followed by leaves. Furthermore, a greater variety of food items and less fruit were consumed in forest fragments. These findings suggest that fruit shortage in fragments results in primates using foods of presumably lower energetic content such as leaves. Similarity in diet was higher among groups geographically closer to each other than among distant groups, showing that the floristic and phenological characteristics of the forest can influence diet composition. We conclude that several years of data are required to fully describe the dietary list of A. geoffroyi at any one site, as studies of the same group over different years shared as little as 56% of species. As most populations of A. geoffroyi live in highly fragmented landscapes, it is crucial to carry out studies in these areas to evaluate (1) changes in diet and activity patterns that may negatively affect survival; and (2) habitat attributes that may favor their persistence in altered landscapes.

Demography, life history and migrations in a Mexican mantled howler group in a rainforest fragment

This paper represents the results of a long-term study (1996-2003) on the demographic changes over time of a Mexican mantled howler (Alouatta palliata mexicana) group in a rainforest fragment (40 ha) in Los Tuxtlas, Mexico, with a follow-up census 3 years later (2006). In addition to demographic and life history parameters, we describe six dispersal events. Our results suggest that this group has been expanding during the study period, growing from six to 12 individuals, with an annual average intrinsic growth rate of 0.07, an infant survivorship of 67%, and an average immature to female ratio of 0.90. This increase in size is probably related to the high food availability in their home range. However, fragment isolation may be negatively affecting the dispersal patterns typical of the species, which could result in a loss of genetic variability over time.

Landscape attributes affecting patch occupancy by howler monkeys (Alouatta palliata mexicana) at Los Tuxtlas, Mexico

Understanding how forest cover is related to patch attributes such as size, shape, and isolation, and how this influences the occurrence of a species in fragmented landscapes is an important question in landscape ecology and conservation biology. To study the effects of fragmentation on patch occupancy by the critically endangered Mexican mantled howler monkey (Alouatta palliata mexicana) in the Los Tuxtlas region of Mexico, we selected three landscapes of ca. 5,000 ha, which differed in their remaining forest cover (24, 11, and 4%). For each landscape, we related patch occupancy to forest cover, patch size and shape, and four isolation parameters. Landscape attributes varied according to forest cover, and the percentage of occupation was greater in landscapes with more forest cover. The attributes affecting the probability of occupancy differed among landscapes. Occupancy was positively related to patch size in all landscapes, but in the northernmost landscape, shape irregularity had a negative effect on occupancy, whereas in the southernmost landscape, occupancy was favored by greater distances to the nearest village. The results show that not only the total amount of forest cover but also patch configuration need to be taken into consideration when designing management strategies for the conservation of the Mexican mantled howler monkey.

Diet and activity pattern of howler monkeys (Alouatta palliata) in Los Tuxtlas, Mexico: effects of habitat fragmentation and implications for conservation

Accelerated deforestation is causing the rapid loss and fragmentation of primary habitat for primates. Although the genus Alouatta is one of the most studied primate taxa under these circumstances, some results are contradictory and responses of howlers to habitat fragmentation are not yet clear. In this paper, we conduct a cross-study of the available researches on mantled howlers (Alouatta palliata) in forest fragments in Los Tuxtlas, Mexico, to (1) describe the diet and activity pattern of howlers; (2) analyze the similarity in the diet across studies; and (3) relate both fragment size and howler population density with different characteristics of their diet, home range size, and activity pattern. Howlers consumed 181 plant species belonging to 54 families. Ficus was the most important taxa in the howlers' diet, followed by primary species such as Pterocarpus rohrii, Nectandra ambigens, Poulsenia armata, and Brosimum alicastrum. Secondary and non-secondary light-demanding plant species, which are representatives of disturbed habitat, contributed with a high percentage of their feeding time. Only 23% of the species consumed were the same across all the studies, suggesting that howlers adapt their diet to the food availability of their respective habitats. Population density is the best predictor of howlers' ecological and behavioral changes in response to forest fragmentation, probably owing to its relationship with food availability. Howlers respond to the increase in population densities by increasing the (1) diversity of food species in the diet; (2) consumption of non-tree growth forms; and (3) consumption of new plant items. Home range size is also predicted by population density, but fragment size is a better predictor, probably owing to the fact that howler groups can overlap their home ranges. Our results emphasize the importance of conserving the larger fragments and increasing the size of small and medium-sized ones.

Glucocorticoid levels in free ranging resident mantled howlers: a study of coping strategies

A growing amount of data shows that a preference for passive-nonaggressive over active-aggressive problem solving is associated with higher levels of glucocorticoids (GC). For mantled howlers, the arrival of an adult male in a new group is a potential source of psychological stress for both resident males and females. Resident mantled howler males take an active stand and aggressively repel the entrance of solitary males, while females take a passive-nonaggressive stand. In order to study whether the relationship between coping strategies and the activation of the hypothalamic-pituitary-adrenal (HPA) axis observed in other species applies to the response of resident mantled howlers to the presence of solitary males, we examine the relationship between different group and subpopulation variables and the GC levels measured in feces collected from 10 groups living in six forest fragments, in Los Tuxtlas, Mexico. The results of our study suggest that the resident mantled howler females' passive response to the presence of solitary males is accompanied by the activation of the HPA axis, whereas resident males' aggressive response is not accompanied by any changes in the HPA axis. In contrast, a previous study suggests that resident male howlers respond by increasing their testosterone levels to the presence of solitary males (Cristobal-Azkarate et al., Hormones and Behavior 2006;49 261-267). These different behavioral and hormonal responses coincide with the active and passive coping styles described for other species. The conditions in which howlers live in our study area may be favoring the interaction between solitary and resident howlers, and inducing chronically high GC levels, which in turn could negatively affect the fitness of these subpopulations.