Habitat use, fruit consumption, and population density of the black-headed night monkey, Aotus nigriceps, in southeastern Peru / Uso de habitat, consumo de frutos, y densidad poblacional del mono nocturno de cabeza negra, Aotus nigriceps, en el sureste de Perú

El mono nocturno de cabeza negra, Aotus nigriceps, tiene uno de los rangos de distribución más grandes de las 11 especies de monos nocturnos que se encuentran en América Central y del Sur. Sin embargo, solo tres estudios se han centrado en su ecología, describiendo una variación considerable en el hábitat, la composición del grupo y la densidad poblacional. Por lo tanto, analisamos el uso de hábitat, la composición del grupo, la densidad poblacional y la dieta de 14 grupos en dos sitios de campo en el sureste de Perú. Todos los grupos muestreados se encontraron en selva tropical secundaria, a menudo dominada por especies nativas de bambú. La mitad de los dormideros observados estaban en bambú, aunque también surgieron grupos de matorrales de caña y lianas. Esto contrasta con otros estudios, que encontraron grupos de Aotus viviendo en cavidades de árboles y lianas. Las estimaciones de densidad poblacional para los dos sitios fueron de 19 y 50 individuos por km2, fuera del rango previamente reportado para A. nigriceps (3134 individuos por km2). Recuperamos semillas de 12 especies de muestras fecales en el transcurso de dos temporadas de campo, pertenecientes principalmente a Cecropiaceae, Piperaceae y Moraceae. Nuestros resultados sugieren que el mono nocturno de cabeza negra puede sobrevivir, e incluso prosperar, en el bosque secundario, alimentándose ampliamente de especies pioneras, ocupando una variedad de tipos de bosque, todo mientras vive a menos de 1 km de asentamientos humanos.(AU)

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 (3134 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.(AU)

Hormonal correlates of development and natal dispersal in wild female owl monkeys (Aotus azarae) of Argentina.

Pair-living and socially monogamous primates typically do not reproduce before dispersing. It is currently unclear whether this reproductive suppression is due to endocrine or behavioral mechanisms. Cooperatively breeding taxa, like callitrichids, may forego reproduction in natal groups because they reap inclusive fitness benefits and/or they are avoiding inbreeding. However, neither of these benefits of delayed reproduction appear to adequately explain the lack of reproduction prior to leaving the natal group in pair-living monogamous species. In this study, we determined whether wild Azara's owl monkeys (Aotus azarae) in the Argentinean Chaco establish reproductive maturity prior to dispersing. We utilized 635 fecal extracts to characterize reproductive hormone profiles of 11 wild juvenile and subadult females using enzyme immunoassays. Subadult females showed hormone profiles indicative of ovulatory cycling and had mean PdG and E1G concentrations approximately five times higher than juveniles. Contrary to expectations from the inbreeding avoidance hypothesis, female owl monkeys do not delay puberty, but rather commence ovarian cycling while residing in their natal group. Still, subadults appear to have a period during which they experience irregular, non-conceptive cycles prior to reproducing. Commencing these irregular cycles in the natal group may allow them to develop a state of suspended readiness, which could be essential to securing a mate, while avoiding costs of ranging solitarily. Our results indicate that reproductive suppression in female owl monkeys is not due to endocrine suppression. We suggest that adults likely use behavioral mechanisms to prevent subadults from reproducing with unrelated adult males in their natal group.

Double effort: Parental behavior of wild Azara's owl monkeys in the face of twins.

In species of mammals that habitually bear single offspring, like most anthropoid primates, the occurrence of twins is expected to impose considerable energetic costs on the caretakers. The question then arises of how caregivers cope with the potentially increased costs of raising twins. These increased costs should lead to differing developmental rates in twins when compared to singletons, and/or to changes in the caregivers' behavior. Likewise, time budgets of parents of singletons are expected to differ from those of adults without offspring. Additionally, if twinning was an adaptive response to favorable ecological conditions, it should be more likely in years with high food abundance. Following the birth in 2011 of two sets of twins in a wild population of pair-living Azara's owl monkeys (Aotus azarae) in Northern Argentina, we used long-term demographic, behavioral, and phenological data to compare (a) the proportion of time that singleton and twin infants were carried by either parent; (b) adult time budgets and ranging behavior in groups with zero, one, or two infants; and (c) the availability of food in 2011 with food availability in other years. Twins, like singletons, were carried nearly exclusively by the male, and they were carried slightly more than singletons, suggesting a relatively inflexible pattern of infant care in the species. Time budgets showed that twin parents foraged more and moved less than singleton parents or groups without infants, despite the fact that phenological data indicate that fruit availability in 2011 was not substantially higher than in some of the other years. Overall, twinning thus presumably increased costs to breeders, especially males, but its effect on animals' long-term reproductive success remains unclear.

Long-term effect of a simple nest-box on the reproductive efficiency and other life traits of an Aotus lemurinus lemurinus monkey colony: an animal model for malaria research.

BACKGROUND: The long-term effect of a PVC pipe nest-box on the reproductive efficiency and other life traits of an Aotus monkey-breeding colony have not been characterized. METHODS AND RESULTS: We analyzed laboratory records of the Gorgas Memorial Institute (GMI) Aotus monkey colony in Panama for the period 1999-2010 and found a 273% increase in the annual mean life births in the following 7 years after the introduction of a PVC pipe nest-box in 2002, as well as increases in the mean body mass and survival of laboratory-bred monkeys. Other life traits such as inter-birth interval, parity, birth sex distribution, mortality, and longevity were also determined. CONCLUSIONS: The use of a PVC pipe nest-box significantly improved the reproductive efficiency and other life traits of the GMI Aotus breeding colony.

Effect of age and number of parturitions on uterine and ovarian variables in owl monkeys.

BACKGROUND: We aimed to evaluate the uterine and ovarian volumes of owl monkeys in different age groups with different numbers of live births and to analyze the interaction between both. METHODS: We performed pelvic ultrasound exams to compare the uterine measurements with weight, age (infant, juvenile, subadult, young adults, and adults) and the number of live births (nulliparous, primiparous, and multiparous) and to compare the ovarian measurements with weight and age. RESULTS AND CONCLUSIONS: The uterine volume (UV) was directly proportional to the number of parturitions, which was the most important factor in the uterine growth of adult females (P < 0.05). The body weight and age of the animals showed a high positive correlation with UV (r = 0.5354, r = 0.6489, P < 0.01), respectively. The volume of the ovaries grew in proportion to the age of the females (P < 0.05). Puberty was the period of greatest uterine and ovarian growth.

Density estimates of Panamanian owl monkeys (Aotus zonalis) in three habitat types.

The resolution of the ambiguity surrounding the taxonomy of Aotus means data on newly classified species are urgently needed for conservation efforts. We conducted a study on the Panamanian owl monkey (Aotus zonalis) between May and July 2008 at three localities in Chagres National Park, located east of the Panama Canal, using the line transect method to quantify abundance and distribution. Vegetation surveys were also conducted to provide a baseline quantification of the three habitat types. We observed 33 individuals within 16 groups in two out of the three sites. Population density was highest in Campo Chagres with 19.7 individuals/km(2) and intermediate densities of 14.3 individuals/km(2) were observed at Cerro Azul. In la Llana A. zonalis was not found to be present. The presence of A. zonalis in Chagres National Park, albeit at seemingly low abundance, is encouraging. A longer-term study will be necessary to validate the further abundance estimates gained in this pilot study in order to make conservation policy decisions.