Óscar M. Chaves

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Here we review all published articles and book chapters, as well as unpublished theses and data of Ateles geoffroyi diet to (1) summarize the literature; (2) synthesize general feeding patterns; (3) document plant taxonomic similarity in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. Am. J. Primatol. 71:8–20, 2009.

Effectiveness of Spider Monkeys (Ateles geoffroyi vellerosus) as Seed Dispersers in Continuous and Fragmented Rain Forests in Southern Mexico

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

Seasonal Differences in Activity Patterns of Geoffroyi´s Spider Monkeys (Ateles geoffroyi) Living in Continuous and Fragmented Forests in Southern Mexico

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

Influence of climatic variables, forest type, and condition on activity patterns of geoffroyi's spider monkeys throughout Mesoamerica

Understanding how species cope with variations in climatic conditions, forest types and habitat amount is a fundamental challenge for ecologists and conservation biologists. We used data from 18 communities of Mesoamerican spider monkeys (Ateles geoffroyi) throughout their range to determine whether their activity patterns are affected by climatic variables (temperature and rainfall), forest types (seasonal and nonseasonal forests), and forest condition (continuous and fragmented). Data were derived from 15 published and unpublished studies carried out in four countries (Mexico, El Salvador, Costa Rica, and Panama), cumulatively representing more than 18 years (221 months, >3,645 hr) of behavioral observations. Overall, A. geoffroyi spent most of their time feeding (38.4 ± 14.0%, mean ± SD) and resting (36.6 ± 12.8%) and less time traveling (19.8 ± 11.3%). Resting and feeding were mainly affected by rainfall: resting time increased with decreasing rainfall, whereas feeding time increased with rainfall. Traveling time was negatively related to both rainfall and maximum temperature. In addition, both resting and traveling time were higher in seasonal forests (tropical dry forest and tropical moist forest) than in nonseasonal forests (tropical wet forest), but feeding time followed the opposite pattern. Furthermore, spider monkeys spent more time feeding and less time resting (i.e., higher feeding effort) in forest fragments than in continuous forest. These findings suggest that global climate changes and habitat deforestation and fragmentation in Mesoamerica will threaten the survival of spider monkeys and reduce the distributional range of the species in the coming decades. Am. J. Primatol. 73:1189–1198, 2011.

Wood Consumption by Geoffroyi’s Spider Monkeys and Its Role in Mineral Supplementation

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

Feeding Strategies of Brown Howler Monkeys in Response to Variations in Food Availability.

Primates display varying degrees of behavioral flexibility that allow them to adjust their diet to temporal changes in food availability. This trait might be critical for the survival of folivorous-frugivorous species inhabiting small forest fragments, where the availability of food resources tends to be lower than in large fragments and continuous forests. However, the scarcity of studies addressing this issue hampers our understanding of the adaptive behaviors that favor the survival of these primates in low-quality habitats. We conducted a 36-mo study testing the hypothesis that brown howler monkeys (Alouatta guariba clamitans) are able to adjust their diet in response to local and seasonal changes in resource availability. We compared the diet of six free-ranging groups inhabiting three small (<10 ha) and three large (>90 ha) Atlantic forest fragments in southern Brazil and estimated the temporal availability of their top food species (i.e., those species that together contribute ≥80% of total feeding records). We found that brown howlers exploited similarly rich diets in small (45, 54, and 57 plant species) and large (48, 51, and 56 species) fragments. However, intermonth diet similarity was higher for groups in small fragments, where howlers also fed on plant items from nine alien species. Fruits and leaves were the most consumed plant items in both small (42% and 49% of feeding records, respectively) and large (51% and 41%, respectively) fragments. The consumption of young leaves was higher in small than in large fragments, whereas the consumption of other plant items did not show a pattern related to fragment size. Regarding the contribution of growth forms as food sources, only the exploitation of palms showed a pattern related to fragment size. Palms contributed more to the diet of groups inhabiting large fragments. The availability of seasonal food items–ripe fruits and young leaves–influenced their consumption in both habitat types. Therefore, brown howlers cope with local and seasonal fluctuations in food availability by opportunistically exploiting resources. We believe that this feeding flexibility is a key component of the phenotypic plasticity that enables howlers to thrive in disturbed habitat patches, where periods of scarcity of preferred foods shall be more common.

Internal and external indicators of male reproduction in the lesser long-nosed bat Leptonycteris yerbabuenae

Abstract Information on animal reproduction is critical for the application of wildlife conservation plans. The lesser long-nosed bat (Leptonycteris yerbabuenae) is classified as threatened in Mexico; however, many aspects of its reproductive biology are still unstudied. The formation of a dorsal patch in males of Leptonycteris spp. during the mating period has been described and evidence suggests this patch is involved in reproductive behavior. We determined the male reproductive cycle of L. yerbabuenae over time based on the seminiferous cycle. We then related these internal indicators with 3 external indicators—testis size, dorsal patch size, and female/male ratio in the population. Finally, we evaluated whether the epididymis functions in long-term sperm storage. Bats were captured monthly and external indicators were registered. Three adult males were euthanized each month for the evaluation of internal indicators. We determined only 1 period of spermatogenesis per year beginning in September and completing in January. The seminiferous epithelium cycle showed 11 stages and 14 steps. Internal reproductive indicators were correlated with external indicators. External testis size and female/male ratio were positively correlated with dorsal patch size. A testis size of approximately 48.2 mm2 corresponded with the beginning of sperm production. The epididymis was not involved in long-term sperm storage. This study provides the 1st description in L. yerbabuenae of the annual timing of the male reproductive cycle based on histological characteristics, and also reports a relationship between the size of the dorsal patch and male reproductive function. Resumen La información sobre biología reproductiva es crítica para la ejecución de planes de conservación de la vida silvestre. El murciélago magueyero (Leptonycteris yerbabuenae) está clasificado como Amenazado en México; sin embargo, muchos aspectos de su biología reproductiva no han sido aún estudiados. La formación de un parche dorsal en machos de Leptonycteris spp. durante el período de apareamiento ha sido descrita y la evidencia sugiere que este parche está vinculado al comportamiento reproductivo. Nosotros describimos la dinámica del ciclo reproductivo de los machos de L. yerbabuenae en base al ciclo seminífero. Posteriormente, relacionamos estos indicadores internos con 3 indicadores externos—tamaño de testículos, tamaño del parche dorsal, y proporción de sexos en la población. Finalmente, evaluamos si el epidídimo funciona almacenando esperma por tiempo prolongado. Los murciélagos fueron capturados mensualmente y se registraron los indicadores externos. Tres machos adultos fueron sacrificados cada mes para la evaluación de los indicadores internos. Detectamos solo un período de espermatogénesis al año comenzando en septiembre y finalizando en enero. El ciclo del epitelio seminífero presentó 11 estadíos y 14 pasos. Los indicadores reproductivos internos mostraron correlación con los indicadores externos. El tamaño externo de los testículos y la relación hembras/machos presentaron correlación positiva con el tamaño del parche dorsal. Un tamaño de testículos de aproximadamente 48.2 mm2 se corresponde con el inicio de la producción de esperma. El epidídimo no está involucrado en el almacenamiento de esperma por tiempo prolongado. Este estudio provee la primera descripción cronológica del ciclo reproductivo masculino en L. yerbabuenae basada en características histológicas, y además evidencia la relación entre el tamaño del parche dorsal y la función reproductiva en machos.

River crossings by Ateles geoffroyi and Alouatta pigra in southern Mexico: A preliminary report

Durante nueve meses evaluamos si los monos arana (Ateles geoffroyi) y los monos aulladores (Alouatta pigra) tenian la capacidad para cruzar uno de los rios mas grandes de Mexico, y si este comportamiento estaba relacionado con la deforestacion y/o el tamano de las poblaciones humanas en la margen alterada del rio. Este estudio se realizo a lo largo del rio Lacantun, sur de Mexico, el cual divide la Reserva de la Biosfera Montes Azules de la region altamente deforestada de Marques de Comillas. Con base en 428 horas de monitoreos a lo largo del rio y en entrevistas a 58 residentes en cuatro comunidades de Marques de Comillas determinamos si los monos eran capaces de cruzar el rio, asi como la frecuencia de estos eventos en ambas especies de monos y su direccion. Ademas, determinamos si este comportamiento estaba relacionado con la tasa de deforestacion y/o el numero de habitantes en los sitios de estudio. Solamente en dos ocasiones observamos monos arana cruzando el rio, de Marques de Comillas hacia la reserva. Sin embargo las entrevistas indicaron que pese a su rareza, este comportamiento ocurria en ambas especies y era mas frecuente en los monos aulladores que en los monos arana (13 versus 8 avistamientos, respectivamente). En los puntos en que se reportaron estos eventos, el ancho del rio fue menor que en otras zonas del rio. Sin embargo, el numero de registros de monos cruzando el rio no estuvo significativamente relacionado con la tasa de deforestacion ni con el tamano de las poblaciones humanas estudiadas. Cualesquiera que sean las causas que promueven este comportamiento, es indudable que estas deben ser lo suficientemente importantes como para que de vez en cuando ambas especies de monos esten dispuestas a tomar el riesgo de cruzar el rio Lacantun.

Spider Monkeys in Human-Modified Landscapes: The Importance of the Matrix

With the extant of tropical forest degradation, primates increasingly inhabit forest patches embedded in anthropogenic matrices. Such matrices are composed of different land cover types (e.g., agricultural lands and cattle pastures), but large uncertainty remains about the ability of primates to use these land covers. Here, we assessed the use of the landscape matrix by spider monkeys (Ateles geoffroyi) in 13 forest sites from three countries (Mexico, Costa Rica, and El Salvador). Based on ad libitum records from >212 months of field observations, we found that spider monkeys used four types of land covers for feeding or traveling: secondary vegetation, isolated trees, tree crops, and vegetation corridors. Secondary vegetation was more frequently used than the other land covers. The number of land covers present in the matrix was positively related to the number of land covers used for traveling and feeding. Monkeys consumed 53 plant species in the matrix, mostly native and old-growth or late-successional forest species, although they also used three cultivated tree species. Most species were trees, especially from preferred food species, although monkeys also used palms, lianas, and shrubs. Monkeys fed principally from fruits, but they also used leaves, wood, and flowers. Most species were used from secondary vegetation and isolated trees. These findings suggest that the landscape matrix can provide supplementary food sources for this endangered primate and opportunities for traveling (i.e., spatial connectivity) in human-modified landscapes—information that can be used to improve conservation strategies, especially under the context of land-sharing management strategies (e.g., agroforestry).

The Darwinian revolution

ABSTRACT The scientific revolution probably began at 16 th century with the heliocentric theory of the eminent astronomerNicolaus Copernicus, but it was culminated with the masterful discoveries of Galileo Galilei and Isaac Newton at17 th century who revealed that planet movements around the sun and other similar phenomena can be explained bysimple mechanical laws of physics and astronomy. However, the origin, complexity and configuration of livingbeings remained in the mystery until 19 th century, with the publication of “On the origin of species”. In this essay Idiscuss the importance of the Darwinian scientific revolution, its beginnings, and the main objections of creationiststo his evolutionary ideas. Darwin demonstrated that the origin and complexity of living beings can be explained bynatural processes, without the intervention of a supernatural being. However, the beginnings of the Darwinianrevolution were particularly difficult and 128 years after his death, the controversy between evolutionists andcreationists still persists.