This study provides evidence that hunting and logging can impose stress on animals. Spider monkeys showed elevated fecal glucocorticoid metabolite (FGCM) levels in forest fragments with high levels of human impact, whereas howler monkeys did not. Glucocorticoid measurements can be a useful tool to monitor wildlife populations in disturbed areas.
As part of a study of responses by red howler monkeys (Alouatta seniculus) to forest fragmentation, we studied red howlers in an extensive forest including a habitat mosaic of old-growth forest, secondary forest of different ages, and non-commercial monospecific plantations of exotic Chinese ash (Fraxinus chinensis) and pines, to produce baseline information on resource use and their role as seed dispersers. We followed three troops for six months, encompassing a dry and a wet season; in total, they fed on 48 species of trees, including fruits, leaves and flowers, but each group relied on a limited set of species available within its home range, particularly in the Moraceae and Cecropiaceae. This contrasts with lowland forest, where howlers feed on a larger variety of species. We observed no season of generalized fruit scarcity, as is the case in the lowlands. However, localized fruit scarcities in howler home ranges occurred. Howlers fed on relatively small quantities of leaves when fruit was available, and became primarily folivorous when fruit was unavailable. Howlers transported a mean of 2.3 species of seeds per fecal sample, to a mean distance of 116 m from the parent tree. More importantly, howlers are transporting seeds to ash and pine plantations, helping to enrich these habitats.
Howler monkeys are among the most studied primates in the Neotropics, however, behavioral studies including estimation of food availability in Andean forests are scarce. During 12 months we studied habitat use, behavior, and feeding ecology of two groups of red howler monkeys (Alouatta seniculus) in an isolated fragment in the Colombian Andes. We used a combination of focal animal and instantaneous sampling. We estimated fruit production (FP) using phenology transects, and calculated young leaf abundance by observing marked trees. The home range area used by each group was 10.5 and 16.7 ha and daily distances traveled were 431 ± 228 and 458 ± 259 m, respectively. We found that both groups spent most of their time resting (62-64%). Resting time did not increase with leaf consumption as expected using a strategy of energy minimization. We did not find a relationship between daily distances traveled and leaf consumption. However, howlers consumed fruits according to their availability, and the production of young leaves did not predict feeding time on this resource. Overall, our results are similar to those found on other forest types. We found that despite limited FP in Andean forests, this did not lead to a higher intake of leaves, longer resting periods, or shorter traveling distances for red howlers.
We studied habitat use and ranging patterns of five red howler monkey troops for six months in a lower montane forest in the Colombian Andes. The study area is a mosaic of mature and secondary forest and non-commercial ash, pine and oak plantations that were established as part of a reforestation program. Home ranges (10 ± 3 ha) and daily distances traveled (554 ± 248 m) were similar to those reported for lowland habitats. Home range use differed between groups using mature forest versus secondary forest and plantations, reflecting structural differences between habitat types. We estimated a density of 0.72 individuals and 0.1 groups per hectare. This high density is related to the protected status of the study area and the howler monkeys’ behavioral plasticity, which has allowed them to colonize new environments such as plantations.
Dieta y comportamiento alimentario de un grupo de mico maicero Cebus apella de acuerdo a la variación en la oferta de frutos y artrópodos, en la Amazonía colombiana Carolina GÓMEZ-POSADA 1 ResumenSe analizó la relación entre la abundancia de artrópodos y frutos maduros, con el comportamiento alimentario y dieta de un grupo de Cebus apella en la Amazonía colombiana durante 1999. La oferta de frutos se midió por transectos fenológicos y la abundancia de artrópodos por capturas manuales. La oferta de ambos recursos varió a lo largo del año, lo que permitió establecer tres períodos de disponibilidad combinada: abundancia, oferta intermedia y escasez. Se completaron 708 horas de seguimiento al grupo y con el método de barrido lento se determinó una dieta omnívora, siendo principalmente insectívora -frugívora (48.8% -42.9%). Los maiceros consumieron 96 especies de plantas y la diversidad mensual de frutos en la dieta, no se correlacionó con la oferta de los mismos. En los meses de abundancia de recursos, tanto frutos como artrópodos fueron consumidos en altas cantidades, y los frutos presentaron una distribución agrupada. Durante los períodos de escasez de recursos, la dieta incluyó pocas especies de frutos, considerados clave, de difícil manipulación, como Cariniana micrantha (Lecythidaceae), y fue complementada con partes vegetales. A diferencia de otros estudios, durante la escasez de frutos, no se presentó el mayor consumo de artrópodos, puesto que éstos igualmente escaseaban. Los maiceros mostraron una dieta generalista -oportunista y utilizaron los recursos en la proporción en la que estuvieron disponibles. Así por ejemplo, los valores de selectividad para frutos fueron muy bajos, y las tasas de éxito de captura de artrópodos se correlacionaron con la disponibilidad de los mismos. PalabRas clave: capuchinos, ecología alimentaria, bosques húmedos de tierras bajas, abundancia de frutos y artrópodos Diet and feeding behavior of a group of brown capuchin monkeys Cebus apella according to fruits and arthropods availability, in the Colombian Amazon abstRactThe relation between the abundance of fruits and arthropods, and the diet and feeding behavior of a group of Cebus apella was studied in the Colombian Amazon during 1999. Fruit availability was measured using phenological transects, and the abundance of arthropods by using manual captures. The abundance of both resources varied throughout the year, which allowed establishing three periods of availability: abundant, intermediate, and scarce availability. 708 hours of monkey observations were completed, and using slow scans, it was determined that they had an omnivorous diet, being principally insectivorousfrugivorous (48.8% -42.9%). Capuchins consumed 96 plant species, and the monthly diversity of fruits in the diet was not correlated with the fruit availability. During months of resource abundance, both arthropods and fruits were eaten in high quantities, and fruits showed clumped distribution. During fruit and arthropod shortage periods, the diet included a few key...
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