American Journal of Primatology最新文献

Conservation education activities employing multimodal knowledge transmission, including art-based workshops, are a multidisciplinary tool that can be used to raise awareness of the natural environment in which we live. In this study, we implemented a conservation education workshop that combined different forms of knowledge transmission, to promote pro-environmental knowledge, attitudes, and behavioral intentions towards spider monkeys and their ecosystem, among 5- to 16-year-old students in a rural school in a Mayan community in Mexico (N = 27). The aim of the study was to (i) develop and implement a workshop tailored to the cultural context of Maya children in México, incorporating artistic activities and multimodal learning approaches, and (ii) evaluate its effectiveness by monitoring changes in participants' knowledge, attitudes, and behavioral intentions towards spider monkeys and their ecosystem. Our findings indicate overall increases in conservation-oriented knowledge and behavioral intentions following the workshop, with more pronounced gains in knowledge among girls and in behavioral intentions among older children. Attitudes toward spider monkeys were already high before the intervention and showed a small but statistically significant increase afterward. Children's drawings reflected increased references to morphological and ecological traits, although aspects related to social behavior and human-monkey interactions were less represented. These outcomes suggest that short-term, culturally embedded and multimodal educational interventions may promote conservation learning in rural communities, though some effects may be constrained by ceiling effects and topic complexity. Future research should explore the durability of these changes over time, the specific drivers of pre-existing pro-environmental attitudes, and the impact of prior familiarity and cultural context on learning outcomes.

The high energy costs of brains suggest that a species' current brain size is adaptive. However, although the comparative data for mammals suggest a positive effect on fitness in larger-brained species because of higher adult survival and thus longer lifespan, it also reveals two negative effects, namely later age at first reproduction owing to slower development and a tendency towards reduced reproductive allocation owing to larger newborns. Here we suggest that what is missing is the positive impact of brain size on immature survival, causally linked to greater parental investment in larger-brained species. Using long-term demographic data on natural populations of 18 primate species, we find a strong positive brain size effect on immature survival, which is already apparent during the first year. We suggest this effect is caused by parental protection and provisioning, allowing young to survive better and mature slowly but surely. This survival effect may well be the strongest adaptive benefit of increased brain size. It remains unknown to what extent this effect generalizes to non-primates.

In stark contrast to our own highly plastic communicative abilities, nonhuman primate vocalizations were historically considered fixed and innate, with very little ability to learn or modify vocal signals. However, recent studies indicate that primate vocalizations do show evidence of developmental plasticity, most notably in their context and usage. We build on these studies by investigating developmental changes in one of the most common calls of white-faced capuchins (Cebus imitator), the twitter. Specifically, we examined the behavioral context around twitter vocalizations in a wild population of white-faced capuchins in the Taboga Forest Reserve, Costa Rica. We analyzed the use of twitters in relation to behavioral state (social, foraging, travel, or resting), immediate context (approaching and leaving others), and specific social behaviors (grooming and aggression). Immatures (infants and juveniles) twitter primarily in a social state, while adults twitter primarily in a foraging state. The twitters produced by immatures were more closely associated with approaching other group members within 1 m, compared to adults. This contextual shift with development from social to foraging prompted us to also look for corresponding acoustic changes. However, the acoustic properties of twitters were not related to context or age, with the one exception that adult twitters were longer than those from immatures. Overall, our results suggest that the twitter is a call with multiple functions, with a shift in usage from social to foraging contexts across development. This adds to the growing evidence of flexibility and learning in primate vocal communication.

The common marmoset (Callithrix jacchus) is a valuable model for studying aging due to its physiological and social similarities to humans, including shared susceptibilities to age-related diseases. However, the effects of healthy aging on marmoset mastication and swallowing are poorly understood, despite their importance for modeling human aging and understanding marmoset ecology and longevity (efficient food processing impacts foraging success and predation risk). Given their specialized diet, dental adaptations, and relatively long lifespan compared with other biomedical models commonly used, like rodents, understanding how elderly marmosets maintain feeding efficiency is particularly important, yet lifespan research on their feeding physiology is scarce. Using cineradiography (with a microfocal X-ray source and beryllium image intensifier), we examined masticatory and swallowing physiology across the marmoset lifespan (1 month to 19 years) in 26 healthy individuals, analyzing 45 recordings (80 feeding events, 784 swallows). Our study revealed a developmental trajectory in marmoset chewing and swallowing, from infancy to old age, characterized by progressively refined handling of larger food portions and boluses. We identified distinct anatomical, functional, and behavioral differences in feeding physiology among age groups. Elderly marmosets exhibited significantly faster feeding rates than infants and adults, consuming larger portions and forming larger boluses, requiring fewer mastications and swallows, likely reflecting age-related adaptations. Notably, old and very old marmosets showed comparable feeding efficiency, suggesting compensatory mechanisms to maintain function despite age-related challenges (e.g., tooth loss or muscle weakness) and may contribute to longevity. The consistent pattern of esophageal retention across age groups indicates this pattern is likely typical for the species. This study establishes baseline feeding characteristics for marmosets, reinforcing their value as a translational aging model and enhancing their utility for investigating age-related changes in human chewing and swallowing, including dysphagia. Future research should explore the underlying mechanisms and functional implications of these changes.

In mammals, estrogens and progestogens are crucial for gestation, fetal development, and maternal preparation for parturition and lactation. Measuring these hormones allows for the diagnosis of pregnancy, estimation of pregnancy failures, and potentially prenatal sex determination. We evaluated urinary estrogen and progestogen metabolites as biomarkers for gestation detection and for their utility for fetal sex determination in wild Assamese macaques (Macaca assamensis) using 586 samples from 19 females, including 19 successful pregnancies. Four enzyme-immunoassays were tested for suitability in measuring urinary sex steroids using serial dilution: three assays targeting progestogen and one targeting estrogen metabolites (estrone conjugates, E1C). We performed a biological validation by measuring urinary hormone metabolites in one female across pre-, early-, late-, and post-gestation. None of the progestogen measurements reflected gestational status, while E1C levels showed the expected increases during gestation. Next, we measured urinary E1C across gestation in all females and investigated fetal sex effects on maternal E1C levels, expecting differences between females carrying male versus female fetuses. Urinary E1C levels increased as early as 9 days postconception and declined sharply at parturition, mirroring patterns in other primates. During late gestation, females carrying male fetuses had significantly higher E1C levels than those carrying female fetuses, yet overlapping values limit precision for prenatal sex determination. Urinary E1C offers a noninvasive marker for gestation monitoring in Assamese macaques, with application in ecological and conservation research. Additionally, results indicate intra- and inter-species-specific differences in steroid hormone metabolism and excretion, which need to be considered when selecting markers for reproductive monitoring.