Biology subjects

Helenbrook, W. D.

Publications and source records attributed to Helenbrook, W. D..

3 recordsLinked to original sources

bioRxiv2020

Species distribution modeling and conservation assessment of the black-headed night monkey (Aotus nigriceps): A species of least concern that faces widespread anthropogenic threats

Deforestation rates in the Brazilian Amazon have been steadily increasing since 2007. Recent government policy, projected growth of agriculture, and expansion of the cattle industry is expected to further pressure primates within the Amazon basin. In this study, we examined the anthropogenic impact on the widely distributed black-headed night monkey, Aotus nigriceps, whose distribution and population status have yet to be assessed. We 1) modeled species distribution in A. nigriceps; 2) estimated impact of habitat loss on population trends; and 3) highlight landscape-based conservation actions which maximize potential for their long-term sustainability. We found the black-headed night monkey to be restricted by several biotic and environmental factors including forest cover, elevation, isothermality, and precipitation. Over the last two decades, over 132,908 km2 of tree cover (18%) has been lost within their documented range. We found this species occupies only 49% of habitat within in their range, a loss of 19% from their estimated 2000 distribution, and just over 34% of occupied areas were in protected areas. Projected deforestation rates of A. nigriceps equates to an additional loss of 23,084 km2 of occupied habitat over the next decade. This study suggests that although classified as a species of Least Concern, A. nigriceps may have a much smaller range and is likely more at risk than previously described. The future impact of continued expansion of mono-cultured crops, cattle ranching, and wildfires is still unknown. However, expanded use of participatory REDD+, sustainable agroforestry in buffer zones, secured land tenor for indigenous communities, wildlife corridors, and the expansion of protected areas can help ensure viability for this nocturnal primate and other sympatric species throughout the Amazon Basin.

ecology↗

bioRxiv2019

Habitat use, fruit consumption, and population density of the black-headed night monkey, Aotus nigriceps, in Southeastern Peru

The study of wild black-headed night monkey (Aotus nigriceps) ecology is limited to a single field station, despite the species being found across a vast distributional range in the Amazon. We studied several aspects of their ecology, specifically habitat use, group size, population density, and diet. All sampled groups were found in secondary tropical rainforest, often dominated by either native bamboo or cane species. Sleeping sites were often in bamboo stands, though groups were also found in cane thickets and lianas. This is in contrast to other Aotus studies which have found groups living in tree cavities and lianas. Population density estimates varied between field sites (19 and 50 individuals per km2), but both were consistent with other Aotus studies (31-40 individuals per km2). And, twelve seed species were recovered from fecal samples over the course of two field seasons, dominated primarily by Cecropiaceae, Piperaceae and Moraceae. Our results suggest that the black-headed night monkey can survive and even thrive in secondary forest, feeding extensively on pioneer species, occupying a range of forest types, all while living in proximity to people (<1km).\n\nRESUMOEl estudio de la ecologia del mono nocturno salvaje (Aotus nigriceps) se limita a una unica estacion de campo, a pesar de que la especie se encuentra en un vasto rango de distribucion en el Amazonas. Estudiamos varios aspectos de su ecologia, especificamente el uso del habitat, el tamano del grupo, la densidad de poblacion y la dieta. Todos los grupos muestreados se encontraron en la selva tropical secundaria, a menudo dominada por bambu nativo o especies de cana. Los sitios donde dormian a menudo se encontraban en puestos de bambu, aunque tambien se encontraron grupos en matorrales de cana y lianas. Esto contrasta con otros estudios de Aotus que han encontrado grupos que viven en cavidades de arboles y lianas. Las estimaciones de densidad de poblacion variaron entre los sitios de campo (19 y 50 individuos por km2), pero ambos fueron consistentes con otros estudios de Aotus (31-40 individuos por km2). Y, doce especies de semillas fueron recuperadas de muestras fecales, dominadas principalmente por Cecropiaceae, Piperaceae y Moraceae. Nuestros resultados sugieren que el mono nocturno de cabeza negra puede sobrevivir e incluso prosperar en bosques secundarios, alimentandose ampliamente de especies pioneras, ocupando una variedad de tipos de bosques, mientras viven cerca de personas (<1 km).

animal behavior and cognition↗

bioRxiv2019

Spatial variation in black-headed night monkey (Aotus nigriceps) vocalizations

Quantitative acoustic analysis has been used to decipher individual differences, population structure, and taxonomic diversity in numerous primate species. We previously described three distinct call types in wild Aotus nigriceps, and now assess acoustic differences in two of these call types between social groups and spatially distinct populations. Acoustic parameters for both analyzed call types exhibited significant variability between groups. Similarly, geographically distant field sites were acoustically distinct from one another. Several groups also used a variation of a common call: a triplet Ch Ch instead of a duplicate. Other groups made use of ultrasonic frequencies which have not previously been reported in Aotus. Our results suggest that Aotus nigriceps exhibits substantial acoustic variability across sites that could potentially be useful for taxonomic classification, although additional geographically distant populations still need to be sampled. The possibility of individual signatures also exists and will require recording vocalizations from known individuals.

animal behavior and cognition↗