American Journal of Primatology最新文献

Primate foraging behaviors are influenced by a variety of factors including the physical and mechanical properties of food items. Golden monkeys (Cercopithecus mitis kandti) inhabiting Volcanoes National Park (VNP), Rwanda, rely heavily on mechanically challenging bamboo shoots and bamboo leaves for the bulk of their diet. We examined the oral processing behaviors of golden monkeys and predicted that bamboo shoots would be characterized by more incising and post-canine crushing behaviors needed to remove tough outer casings and process culms while leaves would require more mastications compared to other food items. We also predicted that juveniles would utilize more incisions and post-canine crushing behaviors to process bamboo shoots and more mastications to process leaves due to the reduced foraging efficiency characteristic of juveniles. We opportunistically filmed habituated groups of golden monkeys foraging during November–December 2022 and January–March 2024 (n = 328 videos). Oral processing behaviors (including incision, canine puncture, post-canine crushing, and mastication scaled to ingestive action) were scored from video footage using Behavioral Observation Research Interactive Software (BORIS). We found that bamboo shoots required more post-canine crushing behaviors compared to other food categories and that non-bamboo leaves required more mastications than bamboo leaves and shoots, respectively. Juveniles did not use more oral processing behaviors per ingestive action, although the inability to control for the size or amount of food ingested may obfuscate these results. Our findings show that golden monkeys adjust their oral processing behaviors to different food items and the routine use of post-canine crushing behaviors may help explain the pronounced tooth wear characteristic of golden monkeys in VNP.

The immature period is an essential time of physical and behavioral development in which individuals prepare to navigate their environment as adults. Activity budgets provide valuable insight into the tradeoffs individuals make based on their energetic priorities. We hypothesized that energetic priorities differ across the stages of development based on the distinct social and ecological needs of that stage. We analyzed 31,113.5 h of focal instantaneous sampling data from 2007 to 2024 on 73 Verreaux's sifaka (Propithecus verreauxi) living in Kirindy Mitea National Park, Madagascar to investigate the effects of age class, sex, and seasonality on activity budgets. Juveniles and subadults devoted significantly more time to social activity than adults. Subadults fed less than other age classes, and we detected no differences in resting among age classes. Among all age classes, males devoted more time to social activity than females, and all age classes displayed sex differences in additional activities. All age-sex classes exhibited similar seasonal patterns in activity budgets. Our results indicate that social activity may be especially important in the developmental period to gain experience and establish social relationships before adulthood. Sex differences in social activity appear to emerge earlier than adulthood as a predisposition for the reproductive roles of adulthood. Overall, we found that energetic priorities differ between stages of development, and evidence is mixed regarding whether these differences are primarily due to the onset of reproduction.

A range of ecological and social factors have been shown to affect early-life behaviour in mammals. Primate infants are altricial and thus unable to move independently at birth. As a result, infants in some species are continuously held or carried (handled) by their mother or another caregiver (allomother). Variation in the amount of time infants move independently can provide insight into the costs and benefits associated with this developmental milestone. In this study, we sought to investigate what environmental conditions are associated with independence in an arboreal primate, the Rwenzori Angolan colobus (Colobus angolensis ruwenzorii). We followed 29 infants from birth until 4 months, collecting data on whether the infant was handled or independent. We report the age-sex make up of infant handlers and show that fruit availability was positively associated with infant independence, and maternal movement frequency was negatively associated with infant independence. We suggest that greater maternal energy balance during early infancy allows mothers to divert more energy to infants, promoting their independent movement. Further research should assess the maternal physiology underlying these trends and whether earlier independent movement has long-term fitness effects.

Tamarins (Saguinus spp., Leontocebus spp.) have been characterized as tolerating or even preferring secondary growth and anthropogenically disturbed areas, and as performing critical seed dispersal in these areas. To test the hypothesis that tamarins prefer secondary growth, we segregated animal presence records by behavior and then used niche modeling to quantify the suitability of various microhabitats for emperor tamarins (Saguinus imperator) and saddleback tamarins (Leontocebus weddelli) over a 315 ha area in the southeastern Peruvian Amazon. Our analysis combines fine-scale maps of key environmental parameters derived from drone-borne lidar data with a behaviorally-sensitive niche modeling of animal movement data measured in the field. This combination allows us to define critical and non-critical areas and gain a new and detailed understanding of microhabitat choice. In saddleback tamarins, we find higher-than-expected use of primary forest for foraging activity. In emperor tamarins, conversely, we find a significant preference for secondary forest in sleeping and unexpectedly high presence in anthropogenically disturbed areas. More broadly, we show that behavioral data lends important nuance to niche modeling methods and that, in combination with fine-scale environmental data, this kind of modeling reveals forms of niche segregation not visible when studying presence alone.

In captive primate facilities, relocations—moves, within the facility, from one cage to another—can be common events. On the one hand, relocations are generally regarded as relatively benign events, as past studies have generally shown only transient elevations in cortisol concentrations following relocation. On the other hand, the frequency of relocations has been associated with adverse health and behavioral outcomes. As part of a larger project examining the effects of stress on follicular development, we relocated adult female rhesus monkeys on a weekly basis for several months in each of 3 years, and measured concentrations of urinary cortisol, epinephrine, and norepinephrine, as well as hair cortisol. Results for urinary cortisol and epinephrine were similar: significant elevations immediately following initiation of relocations during Years 1 and 3, and reductions in concentrations by the end of the relocation sequences in Year 1. No changes were seen for these two measures in Year 2. In contrast, elevated norepinephrine concentrations were found for all 3 years. Significant elevations in hair cortisol concentrations were found for Years 2 and 3, and suggested persisting and cumulative effects of relocations on the hypothalamic−pituitary−adrenal axis. Together, these results suggest that relocations may not be the benign events suggested by earlier studies. Given that all organs of the body are innervated by the sympathetic nervous system (the principal source of norepinephrine in blood and urine) and that cells of the body have glucocorticoid and catecholamine receptors, our results suggest possible mechanisms by which repeated relocations may result in adverse health outcomes. Repeated relocations may be a valuable model for experimentally generating moderate stress; however, we encourage colony managers and scientists to minimize such events to enhance the welfare of the animals.