American Journal of Primatology最新文献

Populations of bearded capuchin monkeys (Sapajus libidinosus) vary in their tool use behaviors, with some of this divergence regarded as culturally determined. The use of stone tools, primarily to crack open encased foods, is widespread among bearded capuchins living in dry habitats (Caatinga and Cerrado). Significant diversity in targets, processed foods, material, and size of tools is observed across populations. However, so far, only a few sites have been systematically studied, and we are still distant from a representative picture of the range of variation in capuchins’ culture. In this study, we did a systematic assessment of stone tool use sites in the Ubajara National Park (UNP), in the Caatinga region of Ceará, Brazil, recording and measuring stone tools, processed foods, and available lithic resources as part of an extensive comparative research, the CapCult project. We found indirect and direct evidence that capuchin monkeys at UNP customarily use hammerstones and anvils to process at least two species of palm nuts, macauba (Acrocomia aculeata) and the harder babaçu (Attalea speciosa). Most of the anvils were rock surfaces and had leftovers of only one palm nut species. The hammerstones used to process both palm nuts were not significantly different in weight, although the ones used for Ac. aculeata were longer. We found a higher frequency of nut-cracking sites in the drier lowland area of the park, reflecting differences in the density of the most common palm species, Ac. aculeata, and availability of raw stone material. The stone tool use observed in UNP is within the scope of previously reported in savannah capuchin populations. Our study widens the knowledge of stone tool-use diversity in wild capuchin monkeys, which could contribute to shaping conservation policy, including cultural traits.

Ways to support professional capacity of emerging conservation leadership in primate range countries.

Individual differences of infant temperament have been associated with future health outcomes that provide explanatory power beyond adult personality. Despite the importance of such a metric, our developmental understanding of personality-like traits is poor. Therefore, we examined whether young primates show consistency in personality traits throughout development. We replicated a Biobehavioral Assessment (BBA) at three time periods: 3–4 months, 1 year, and 2 years of age in 47 rhesus macaque (Macaca mulatta) subjects from large mixed-sex outdoor social housing units at the California National Primate Research Center. We report results for tests focused on responses and adaptation to the temporary separation and relocation, responses to a threatening stimulus, and ratings of overall temperament. We found consistently repeatable associations in measures of Emotionality; these associations were stronger in males, but also present in females, and broadly consistent between Years 1 and 2. We also explored whether behavioral responses to this experimental relocation might be influenced by their experience being relocated for other reasons (i.e., hospitalizations) as individuals' responses might be influenced by similar experiences to the BBA procedure. Only locomotion, during one of the assessments, was associated with past hospitalization events. Overall, repeatability in Emotionality-associated behaviors was evident across the 2 years, in both sexes. We did, however, find evidence of the emergence of sex differences via differentiated expression of behavioral responses during the BBA. We emphasize that there is likely contextual nuance in the use of these BBA factor-associated behaviors. Further research is required to determine whether and how shifts occur in underlying factor structure and the expression of associated behaviors.

Tool-using primates often show sex differences in both the frequency and efficiency of tool use. In species with sex-biased dispersal, such within-group variation likely shapes patterns of cultural transmission of tool-use traditions between groups. On the Panamanian islands of Jicarón and Coiba, a population of white-faced capuchins (Cebus capucinus imitator)—some of which engage in habitual stone tool use—provide an opportunity to test hypotheses about why such sex-biases arise. On Jicarón, we have only observed males engaging in stone tool use, whereas on Coiba, both sexes are known to use tools. Using 5 years of camera trap data, we provide evidence that this variation likely reflects a sex difference in tool use rather than a sampling artifact, and then test hypotheses about the factors driving this pattern. Differences in physical ability or risk-aversion, and competition over access to anvils do not account for the sex-differences in tool-use we observe. Our data show that adult females are physically capable of stone tool use: adult females on Coiba and juveniles on Jicarón smaller than adult females regularly engage in tool use. Females also have ample opportunity to use tools: the sexes are equally terrestrial, and competition over anvils is low. Finally, females rarely scrounge on left-over food items either during or after tool-using events, suggesting they are not being provisioned by males. Although it remains unclear why adult white-faced capuchin females on Jicarón do not use stone-tools, our results illustrate that such sex biases in socially learned behaviors can arise even in the absence of obvious physical, environmental, and social constraints. This suggests that a much more nuanced understanding of the differences in social structure, diet, and dispersal patterns are needed to explain why sex-biases in tool use arise in some populations but not in others.

Salivary alpha-amylase (sAA) is an enzyme found in saliva and is considered a noninvasive biomarker for sympathetic nervous system activity. While a wide range of sAA activity in response to stress has been reported in nonhuman primates, the effects of stress on sAA activity in common marmosets are still unknown. We tested the hypothesis that advanced age and cognitive function may have an impact on stress-related sAA reactivity in marmosets. Thirteen marmosets (nine males and five females) had saliva samples collected during a stressful condition (manual restraint stress) at two different time points, with a 60-min interval. On the next day, the animals underwent the object recognition test (ORT, a type of cognitive test), and then oral examinations. The animals were categorized into two age groups: old (10–13 years), and very old (15–22 years). Irrespective of age, sAA levels showed a significant difference between T1 (mean 2.07 ± 0.86 U/mL) and T2 samples (mean 1.03 ± 0.67 U/mL), with higher values observed at T1 (p < 0.001). The intra-assay coefficients of variation (CV) for low and high sAA concentrations were 10.79% and 8.17%, respectively, while the interassay CVs for low and high sAA concentrations were 6.39% and 4.38%, respectively. Oral health issues were common but did not significantly impact sAA levels. The ORT indicated that the animals could recognize an object placed in the cage 6 h after familiarization. In conclusion, all marmosets showed a higher sAA concentration in the first saliva sample as compared to the second saliva sample collected 1 h later, indicating adaptation to stress. No significant differences in sAA levels were observed between sexes, ORT performance, or oral health. Our results indicate that autonomic responsivity and cognitive (memory) functions were preserved even in very old marmosets.

Ranging dynamics are physical and behavioral representations of how different socioecological factors affect an organism's spatial decisions and space use strategies. Western lowland gorillas (Gorilla gorilla gorilla) are a model species to investigate the drivers of spatial dynamics based on both the natural variation in socioecological factors within the species and compared with their mountain gorilla counterparts. In this study, we evaluate the influences of resource seasonality and social dynamics on variation in home range size, utilization, and intergroup overlap among multiple gorilla groups over an 8-year study period in the northern Republic of Congo. This study shows that western lowland gorillas can have small home ranges comparable to mountain gorillas, rather than universally larger home ranges as previously supposed, and that home ranges are stable through time. The largest source of variation in space use was the degree of intergroup home range overlap. The study groups did not demonstrate intraspecific variation in range size nor changes in intergroup overlap with respect to seasonality of fruit resources, but all groups demonstrated expansion of monthly range and core area with group size, matching predictions of intragroup feeding competition. These findings highlight the potential impact of intergroup relationships on space use and prompt further research on the role of social dynamics in ranging strategies. In this study, we reveal a greater degree of variability and flexibility in gorilla ranging behavior than previously realized which is relevant to improving comparative studies and informing conservation strategies on behalf of these endangered primates.

The golden-headed lion tamarin (Leontopithecus chrysomelas) is an endangered primate that occurs exclusively in the Atlantic Forest of southern Bahia, Brazil. Its geographic range has been severely reduced by deforestation and its populations are restricted to a human-modified landscape consisting primarily of Atlantic forest fragments and shade cacao (Theobroma cacao) agroforestry, locally known as cabrucas. In the last 30 years, there has been a 42% reduction in the geographic range and a 60% reduction in the population size of L. chrysomelas, with only 8% of its habitat represented by protected areas. Thus, we investigated the occurrence of L. chrysomelas in forest fragments and cabrucas based on interviews and using playback census, and evaluated the influence of landscape attributes on its occurrence. The occurrence was measured using a Generalized Linear Model using a set of 12 predictor variables, including fragment size and elevation. L. chrysomelas inhabited 186 (38%) of the 495 forest fragments and cabrucas. Most inhabited habitat patches (n = 169, 91%) are in the eastern portion (ca. 70 km wide region from the Atlantic coast to inland) of its geographic range. The remaining (n = 17, 9%) are in the western portion of the distribution, between 70 and 150 km from the Atlantic coast. Our models indicate a higher occurrence of L. chrysomelas in the eastern portion of its geographic range, where the landscape exhibits lower land cover diversity, greater functional connectivity, lower altitudes (<400 m), and is primarily composed of forest fragments and cabrucas with a higher core percentage. In contrast, we observed a lower occurrence of L. chrysomelas in the western portion, where the landscape is more diverse and heterogeneous due to anthropogenic activities, such as agriculture and livestock. We urge the establishment of ecological corridors via reforestation of degraded areas in the western portion of the range. This increase in habitat availability and suitability in the west together with the protection of the forests and cabrucas in the east would increase our chances of saving L. chrysomelas from extinction.

Researchers and veterinarians often use hematology and clinical chemistry to evaluate animal health. These biomarkers are relatively easy to obtain, and understanding how they change across healthy aging is critical to clinical care and diagnostics for these animals. We aimed to evaluate how clinical biomarkers from a chemistry profile and complete blood count (CBC) change with age in common marmosets (Callithrix jacchus). We assessed blood samples collected during routine physical exams at the Southwest National Primate Research Center and the University of Texas Health San Antonio marmoset colonies from November 2020–November 2021. We found that chemistry and CBC profiles varied based on facility, sex, and age. Significant changes in albumin, phosphorus/creatinine ratio, albumin/globulin ratio, amylase, creatinine, lymphocyte percent, hematocrit, granulocytes percent, lymphocytes, hemoglobin, red cell distribution width, and platelet distribution width were all reported with advancing age. Aged individuals also demonstrated evidence for changes in liver, kidney, and immune system function compared with younger individuals. Our results suggest there may be regular changes associated with healthy aging in marmosets that are outside of the range typically considered as normal values for healthy young individuals, indicating the potential need for redefined healthy ranges for clinical biomarkers in aged animals. Identifying animals that exhibit values outside of this defined healthy aging reference will allow more accurate diagnostics and treatments for aging colonies.

Performance in cognitive tasks has been linked to differences in species' social organization, yet to understand its function its relationship to within-species variation in behavior should also be explored. One important cognitive capacity, the ability to inhibit impulses, is typically better in egalitarian than despotic primate species and in primate species with strong fission-fusion dynamics. A different line of research indicates that a high ability to inhibit impulses is related to less aggressive behavior and more socio-positive behavior. However, within species the relationship between performance on cognitive inhibition tasks and variation in social behavior remains to be explored. Here we investigate how performance in a typical inhibition task in cognitive research is related to aggressive and socio-positive behavior in despotic long-tailed macaques. Twenty individuals living in two naturalistic mixed-sex groups were tested with the Plexiglass Hole Task. Aggressive behavior and three types of socio-positive behavior (neutral/friendly approaches, socio-positive signaling, and grooming others) among group members were measured. Individuals differed in their ability to inhibit impulses. Individuals that were not good at inhibiting impulses showed higher rates of aggressive behavior, but also more socio-positive signals, whereas inhibition was not related to neutral/friendly approaches and grooming. These results confirm the positive link between impulsiveness and aggression. In addition, the results indicate that some social-positive behavior may be enhanced when inhibition is limited. In this species, benefits potentially derived from aggression and socio-positive signals match a low ability to inhibit impulses, suggesting that a low ability to inhibit impulses may actually be advantageous. To understand differences between species in cognitive skills, understanding the benefits of variation in a cognitive capacity within a species is crucial.

We review the evidence that long-tailed macaques are at risk of extinction and find that papers supporting this argument present no data supporting a hypothesized decline in abundance. These papers contain numerous misrepresentations of the published literature. Long-tailed macaques thrive in human-altered habitats, are listed by the International Union for the Conservation of Nature as an invasive species of concern, and have shown the ability to increase by 7%–10% per year from low numbers, making the probability of extinction very low.