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

Abstract

The black-headed night monkey, Aotus nigriceps, has one of the largest distribution ranges of the 11 night monkey species found across Central and South America. Yet, only three studies have focused on their ecology, describing considerable variation in habitat, group composition, and population density. Therefore, we analyzed habitat use, group composition, population density, and diet of 14 groups at two field sites in southeastern Peru. All sampled groups were found in secondary tropical rainforest, often dominated by native bamboo species. Half of the observed sleeping sites were in bamboo stands, though groups also emerged from cane thickets and lianas. This contrasts with other Aotus studies which have found groups living in tree cavities and lianas. Population density estimates for both sites were 19 and 50 individuals per km2, outside the range previously reported for A. nigriceps (31−34 individuals per km2). We recovered seeds of 12 species from fecal samples over the course of two field seasons, belonging mainly to Cecropiaceae, Piperaceae and Moraceae. Our results suggest that the black-headed night monkey in Peru can survive and even thrive in secondary forest, feeding extensively on pioneer species, occupying a range of forest types, all while living near human settlements.

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

“…Current population estimates using modeled viable habitat coupled with density estimates from previous studies (i.e., 19-50 individuals per km 2 ) range from 14,818,822 to 38,996,900 individuals (Helenbrook et al, 2020). Based on contraction of suitable habitat between 2000-2018, we estimate a loss of 3,326,672-8,754,400 individuals.…”

“…Agroforestry research related to night monkey species is limited, though a study in the northern Andes suggests that coffee plantations can benefit night monkeys while also providing farmers with income (Guzmán et al, 2016). We have previously documented that the black-headed night monkey is quite common in secondary forest and that they make use of orchards (Helenbrook et al, 2020). The main issue would appear to be whether connected canopy is maintained in order for night monkeys to traverse a complex matrix with forest fragmentation and diverse land uses.…”

“…1). We used several available sources, including published manuscripts (Wright 1996; Helenbrook et al 2020) and field records provided by the Wildlife Conservation Society and iNaturalist (Lopez-Strauss et al, 2016) (Fig. 2a).…”

“…2013), and 2) calculated the area of their occurrence between 2000 and 2018 using the MaxEnt modeled species distribution. We then used upper and lower population density estimates obtained from Helenbrook et al (2020) to extrapolate across projected habitat using area of occurrence calculations. Future deforestation projections in the Brazilian Amazon were based on rates calculated by Butler (2020).…”

“…Aotus nigriceps is a wide-ranging nocturnal monkey species found across much of the central and upper Amazon, including degraded forest, agroforested landscapes, and areas in close proximity to humans (Helenbrook et al, 2020). Nevertheless, while night monkeys are adaptable and persist in degraded landscapes, they still require connective forest cover, access to seasonally available fruiting trees, sleeping sites, and are restricted by environmental conditions (Aquino & Encarnación 1994; Helenbrook et al, 2020). Although thought to be a common species, it is currently listed as Appendix II of CITES, and the impact of anthropogenic disturbances on the long-term viablity of A. nigriceps remains unknown.…”