Primate conservation requires a better knowledge of the distributions and statuses of populations in both large areas of habitat and in areas for which we currently have no information. We focused on spider monkeys (Ateles geoffroyi) and howler monkeys (Alouatta palliata) in the state of Oaxaca, Mexico. This Mexican state has protected large tracts of forest, and has historical records for both primates, although very little is known about them. To update our knowledge of the distributions of these primates and identify potential areas in which they are present, we modeled their geographic distributions by characterizing their ecological niches using the genetic algorithm for rule-set production (GARP), performed interviews and carried out field surveys. The predicted distributions, surveys and interviews indicate that the distributions of these primates are restricted to northeastern Oaxaca. The results suggest that spider monkeys occupy a wider area and elevational range than howler monkeys. Throughout that range there is a wide variety of suitable habitats for these primates. Most of the sites where monkeys were recorded in the field are not officially protected and there was evidence of hunting and habitat destruction. It is important to improve protection, economic alternatives and environmental education as we move towards an integral solution for the conservation of these species. Validation of the GARP model was done for A. geoffroyi, since we had obtained enough field data for this species; this validation indicated that the predicted distribution of the species was statistically better than expected by chance. Hence, ecological niche modeling is a useful approach when performing an initial assessment to identify distribution patterns, detecting suitable areas for future exploration, and for conservation planning. Our findings provide an improved basis for primate conservation and productive fieldwork in Oaxaca.

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The presence of spider monkey (Ateles geoffroyi) has been verified in the northeast of the state of Oaxaca. However, the information to assess their conservation status is scarce. This study focused during one year on the population census and habitat use of A. geoffroyi in a well-preserved fragment of evergreen forest. We used the distance sampling in line transects method to estimate the density of this primate, and instantaneous scan sampling to collect data of grouping, diet and activity patterns. We estimate a density of 84 spider monkeys/km 2 , which would imply a population size of 586 spider monkeys in a protected area of 7 km 2 , which is part of a continuous forest area of 41 km 2 . This population density is one of the highest reported for the genus Ateles, particularly for the species A. geoffroyi. The average subgroup size was 3.5 independent individuals and their most frequent composition was mixed, with one or more adult females, some with their infant, and one or more independent males. Spider monkeys dedicated a similar proportion of their daylight time to moving (30%) and feeding (22%) as they did to resting (48%). Diet was mainly frugivorous (84% of feeding time) including 30 plants morphospecies. These results suggest that the spider monkey population we have studied is potentially viable.

Determinamos la densidad de población del venado cola blanca Odocoileus virginianus oaxacensis y caracterizamos su hábitat en cuatro asociaciones vegetales en un bosque templado de la Sierra Norte de Oaxaca. Usamos el método de conteo de excretas en transectos lineales para obtener la densidad, y el de cuadrantes centrados en puntos para evaluar las variables vegetales y físicas del hábitat de la especie. La densidad promedio en el periodo de junio de 1998 a agosto de 1999 en el área de las cuatro asociaciones vegetales fue de 1.13 ± 1.15 venados/km2. La densidad de venados no presentó diferencia significativa entre las cuatro asociaciones de vegetación (H = 2.737; P = 0.43). Sin embargo, se observaron valores más altos de la densidad (1.73 venados/km2) en relación a las asociaciones de vegetación Abies-Pinus y Quercus-Pinus, en las cuales la cobertura y volumen de arbustos, así como la sinuosidad en el terreno fueron significativamente mayores que en las asociaciones Pinus- Quercus (0.34 venados/km2) y Pinus-Abies (0.71 venados/km2). Los transectos localizados en la asociación vegetal Abies-Pinus se caracterizaron además por presentar un estrato arbóreo denso, diversidad vegetal alta y distancia corta a una fuente de agua permanente (promedio 153 m). Comparando las características de hábitat entre las cuatro asociaciones vegetales, en las asociaciones Abies-Pinus y Quercus-Pinus los venados pueden encontrar mayor disponibilidad de alimento y cobertura de protección horizontal y vertical, además de una topografía favorable para escapar de los depredadores. Sugerimos que diferentes factores como la productividad del bosque afectada por la sequía de 1998, el estrés asociado a los métodos de caza, y las actividades humanas aledañas al bosque templado del área, pudieron tener un efecto agregado sobre la densidad del venado.