Resumen: Debido a la escasa información en vida silvestre de las especies de primates en el Estado de Tabasco, as! como la conversión de las selvas en pastizales y áreas de cultivo provocando la fragmentación del hábitat de estas, se hace evidente la necesidad de conocer (as poblaciones en vida libre así como su estructura poblacional. Es por esto la importancia del presente estudio, en el cual se da a conocer la distribución y densidad poblacional de Ateles geoffroyi vellerosus y Alouatta pigra así como la perdida de la vegetación en una porción de la Sierra de Poana, Tacotalpa, Tabasco, siendo este el primer registro científico de la existencia de estas especies en este lugar. EI periodo de estudio comprendió los meses de mayo a agosto del 2003, visitándose los Ejidos de Poana, Pomoca, Lomas Alegres 3era y RIA Santa Rosa, Estación Poana; abarcándose una porción de la Sierra Poana. Se registraron un total de 19 poblaciones de primates silvestres (n=100 indiv.), una de ellas perteneció a un subgrupo de A. g. vellerosus (n=4 indiv.) y 18 tropas a A. pigra (n=96 indiv.), asimismo fue posible avistar individuos solitarios de ambas especies. Se observó una mayor densidad relativa de A. pigra, también fue notable la disminución de la vegetación en cada uno de los fragmentos en donde fue posible avistar estas especies. Todo esto nos sugiere que A. pigra presenta una flexibilidad conductual y adaptativa a los hábitat fragmentados, a la presencia del hombre y sus actividades antropogenias; a diferencia de A. g. vellerosus el cual parece estarse viendo afectado por la fragmentación de su hábitat.

Resumen: La perturbación del hábitat expone a los primates a factores adversos, aumentando su riesgo de extinción. Sin embargo, la mortalidad de primates puede deberse a diversos factores no naturales en paisajes fragmentados, donde los monos se observan desplazándose por el suelo, sobre alambres de púas y atravesando carreteras (para trasladarse, alimentarse o beber agua). Durante el 2008-2009 se evalúo la mortalidad de monos aulladores mediante 66 entrevistas semi-estructuradas y recorridos de campo para observaciones directas en seis poblaciones humanas, donde se registraron muertes y sus causas. El 39.4 % de los entrevistados reportaron entre uno y tres eventos de mortalidad, lográndose registrar la muerte de 45 individuos. Las causas de muerte reportadasfueron ataque de perro, agresión humana, agresión intraespecífica y atropellamientos. Por medio de las entrevistas se obtuvo como las principales causas de muerte al ataque de perros (n= 22) y a la agresión humana (n= 14), en los recorridos de campo se observaron directamente 27 muertes de las cuales 10 fueron causadas por ataques de perros, cinco por atropellamientos, dos por agresión intraespecífica, dos por agresión humana y ocho por causas desconocidas. Los resultados obtenidos sugieren que debido a una discontinuidad de la estructura arbórea, cercanía a los asentamientos humanos y un alto número de perros ferales, los “ataques por perros y agresión humana”, fueron muy frecuentes. Se sugiere un plan de conservación mediante el establecimiento de corredores en los sitios de desplazamiento de los monos observados, y otras medidas de conservación aplicadas con anterioridad en poblaciones animales en situaciones similares.

Resumen: En el presente estudio se evaluó si la ingestión y el paso por el tracto digestivo de semillas de frutos silvestres consumidos por Alouatta pigra tiene alguna influencia en el incremento de la velocidad y el porcentaje de germinación, al comparar semillas extraidas directamente de frutos y puestas a germinar.

Resumen: I approached my study of the Central American black howler monkey (Alouatta pigra) from an ethnoprimatological perspective. While my first question considered the presence or absence of howlers in the Lacandon rainforest surrounding Nahá, I also thought it important to consider not only howler ecology, but also Lacandon Maya ecology in Nahá and in the surrounding forest. Whether or not howlers and humans intersect, and the extent to and manner in which they do, is pertinent to howler conservation. The status of howlers is affected by the actions of humans, and if howlers are currently present in the Lacandon rainforest, then they must share resources with humans. In addition to shared resources, human predation of howlers is a necessary consideration. If howlers have recently returned to the Nahá region, hunting could quickly decimate small populations that have yet to become fully established. If forest conditions are less than optimal, even low levels of hunting would further exacerbate ecological pressures for howlers. My study consisted of three parts: census walks, botanical analysis and interviews with local Lacandon Maya. I expected that by conducting census walks, I would be able to determine whether or not A. pigra had returned to the Nahá forests and, in addition, be able to estimate population density. If howlers had returned to the forests, I would also expect that there would be food resources present. However, the future success of any new populations of howlers would require that not only would appropriate plant species be available, but that these species would also be of sufficient size and be present at adequate densities to maintain healthy A. pigra populations. If howlers had recently returned to the Nahá region, the current population density would potentially increase over time as long as conditions were favorable. Long-term access to food is one of the obvious conditions that would allow for an increase in the number of animals that the forest could support. Therefore, I established a primary botanical plot to determine potential resource availability for current and future howler troops. Moreover, I established a second botanical plot and used it, in conjunction with the first, to determine whether or not there were trees of sufficient size to allow howlers to travel through the forest and to access resources.A second condition important to the potential success of howlers in an area where they are sympatric with humans is that the prevailing perceptions and practices of humans must allow for the coexistence of howlers and humans within a common ecosystem. My goal was to determine current Lacandon resource use to elucidate the extent to which howlers and humans in this region rely on similar resources and, furthermore, to ascertain current levels of Lacandon predation of howlers. In addition, I wanted to find out what were the local people’s perceptions of howlers and if their ideas about the presence of howlers in their forest had changed over time. I examined the perceptions and practices of the local villagers across generations by selecting for my interviews individuals who represented varying age categories. Human ecology and howler ecology need to be compatible if humans and howlers are to have a successful sympatric relationship. In other words, both species’ survival requirements have to be met. It is possible that Alouatta pigra could return to the forest surrounding Nahá and subsequently experience levels of stress that are not conducive to maintaining healthy populations, either due to an inadequate environment or to hunting pressures. By utilizing an ethnoprimatological approach, I hope to elucidate the extent to which a sympatric relationship is possible between humans and A. pigra in the Nahá forest region.

Resumen: Three social groups of howler monkeys (Alouatta pigra) were estudied in Calakmul Archeological Zone within the Calakmul Biospehre Reserve in the southeastern portion of the Yucatan peninsula Campeche, Mexico. The prupose of this study was examine the social behavior, feeding and ecology of this species within a non-fragemented habitat free from the threat of human encroachment. A seres of non-invasive intensive observations was performed during June and July 2001 and January and Febraury 2002 as representative of the natural wet and dry seasons, respectively. Data was collected on the social organization, group composition, diet and activity patterns of each social group. The activity patterns observed for the study groups were within previously reported ranges for all species of Alouatta. The study group' activity patterns at Calakmul compare with other species of Alouatta providing those comparisons are made during the we season.That is, the time spent in travel, rest and feeding for the study populations are comparble to the wet season activity patterns for the other species of howler. In contrast, observations of absence of dawn and dusk vocalizations, male biased infant sex ratios, high degree of frugivory and disproportionate number of adult males in two of the study groups are unique to this research. The consistency of a highly frugivorous diet for these study groups was directly related to the annual availability and diversity of fruit available at calakmul. The high ratio of adult males per social group along with the male blased infant sex ratio may indicate that males are philopatric while females are the dispersing sex for these groups of howlers. By far the most significant contribution of this study is the first description of sentry male behavior. This proximal spacing of adult males relative to the rest of their group appears to be a ubiquitous feature to this population. Adult males of each study groups separeted themseleves from the rest of the group. From these proximal locations adult males visually manitored the surrounding area for any potential invaders. Indeed, there may be a correlation between sentry behavior and the lack of dawn and dusk vocalizations. This study expands our definition of Alouatta and dispels the myth of the "typcal" howler.