American Journal of Primatology最新文献

Self-directed behaviors (SDBs) are commonly used as reliable indicators of anxiety, frustration, and stress in nonhuman primates. These behaviors are typically observed in stressful situations, such as being in close proximity to dominants or during post-conflict. However, there is limited evidence on whether individuals increased their SDBs before engaging in potentially risky behaviors. In this study, we used a focal sampling method to record and analyze SDB rates in wild Tibetan macaques (Macaca thibetana) before approaching another group member (as a proxy for potentially risky behavior). Specifically, we examined the 5-min period (selected from focal samplings) before approaching a conspecific to address two main questions: (1) how rank and kinship affect SDB rates before approaching behavior, and (2) when individuals exhibit the highest anxiety, as indicated by peak SDB rates. Our results show that: (1) both males and females exhibited higher rates of SDBs before approaching a higher- than a lower-ranking group member of the same sex; (2) females showed no difference in SDB rates before approaching a female kin (sister or mother/daughter) compared to approaching a non-kin; (3) lower-ranking males exhibited higher SDB rates when approaching a receptive female, but not when approaching a non-receptive female; (4) females showed the highest SDB rates in the last minute (minute 5) before approaching a higher-ranking female. These findings suggest that Tibetan macaques increase their SDBs before engaging in potentially risky behaviors, providing an insight into the psychological state of an individual who is about to engage in a social interaction.

Frugivorous primates may consume unusual food items, such as plant galls, to meet their nutritional requirements; yet, the contributions of these dietary components to their diet, nutrition requirements, and energy intakes are still unclear. We documented the importance of plant galls in these aspects for black-and-white ruffed lemurs (Varecia variegata) in a Malagasy rainforest. Using daily observation data of lemur foraging and nutritional analyses of their consumed items, we measured (1) the proportion of galls in their diet, (2) the rate at which they acquire nutrients and energy from galls compared to other food items, and (3) the changes in their diet patterns and acquisition of nutrients and energy with the consumption of galls. We also investigated whether they are more likely to consume fruits on trees with galls and characterized whether galls have similar characteristics as fruits. We found that plant galls constituted 12.96% of the lemur feeding occurrences; and on some days, lemur diets comprised galls only. Also, the lemurs acquired from galls higher protein than any other food items and higher sugar, fiber, and energy than leaves, but lower lipid than fruits and similar nutrients and energy as from flowers. The addition of galls in their diet significantly reduced their consumption of ripe fruits on a daily basis and increased the acquisition of protein, sugar, fiber, and energy. Also, lemurs were more likely to consume fruits on trees with galls than expected, likely due to similarities in color and nutrient components between galls and fruits in this system. These findings enhance our understanding of the nutritional needs and food selection behavior of primate frugivores. Such knowledge has implications for developing strategies to maintain primate populations in their natural environments and potentially to ensure the welfare of captive animals in ex-situ conservation settings.

Facilities may forgo attempting to socially house adult males due to fear of animal injury, study disruptions, and confounding data results. To leverage the potential advantages of male–female pairs, and to understand the impact on measures typically used in safety pharmacology studies, we measured activity as well as physiologic parameters in vasectomized male-female pairs: heart rate, blood pressure, and body temperature. Seven singly housed males that were previously implanted with telemetry were vasectomized and paired with females. Data were collected before and after pairing at specific timepoints in the first study. A second study employed four nonvasectomized, singly housed males to determine if the physiologic effects observed in the first study could be due simply to the increased cage size due to pairing. Results indicated that pair-housing with a female resulted immediately in a significant increase in blood pressure, body temperature, and heart rate. Over the course of a week of being paired, the males showed a significant decline in blood pressure; body temperature remained elevated, though at a lower level than during the immediate response. The second study suggested that increased cage size alone could not account for the immediate results in Experiment 1, inasmuch as no effects were found on our measures. Although the sample sizes for the studies were small, we discuss how our results are similar to, and differ from, previous studies, as well as the clinical significance and welfare implications. This information may be useful in designing long-term studies using sexually mature males while providing stable social support to animals.

Grooming is the most common affiliative behavior in many primate species. While traditionally viewed as an exclusively dyadic interaction, polyadic grooming involving more than two individuals also occurs. Few studies have explored the characteristics or functions of polyadic grooming in comparison with dyadic grooming. However, some studies suggest that polyadic grooming may have distinct characteristics and could be associated with social tolerance. We analyzed polyadic grooming patterns and its network structure in a free-ranging group of Japanese macaques at Awajishima, Japan. This group exhibited higher social tolerance than typical Japanese macaque groups. We found that polyadic grooming was common in this group, with higher frequency than other Japanese macaque groups as well as other primate species except chimpanzees. We also found that polyadic grooming typically occurred with multiple groomers sharing a single groomee, a pattern commonly observed across most primate species. Social network analyses showed that the polyadic grooming network was centralized around high-ranking males, reflecting the frequent grooming from multiple females to a single adult male. In addition, the network of polyadic grooming was less dense and more cliquish than that of dyadic grooming. This potentially suggested that polyadic grooming was more strongly kin-biased than dyadic grooming. Our results support the prediction that polyadic grooming may be associated with higher levels of social tolerance. Moreover, polyadic grooming may function to access valuable social partners more efficiently than dyadic grooming.

The evolution of human musicality has attracted immense and intense cross-disciplinary research attention. However, despite widespread interest, there has been surprisingly little explicit focus on the conserved roots and evolutionary precursors of musicality in our closest relatives, chimpanzees (Pan troglodytes) and bonobos (P. paniscus). We here aim to evaluate the extant literature on chimpanzees and bonobos in behavioral contexts relevant to evolutionary theories of musicality, especially simultaneous production of acoustics signals by multiple individuals (“collective acoustics”). We illustrate the importance of this literature by evaluating and comparing a pair of recent, influential, and competing theories on the evolution of human musicality (music for social bonding and music for credible signaling) in light of the reviewed empirical evidence. We conclude by highlighting core remaining questions for future empirical studies on great ape collective acoustics that may have a critical influence on our understanding of the evolution of human musicality.

Characterizing patterns of genetic diversity and gene flow is crucial for understanding the movements of dispersing individuals, and for assessing population viability and informing conservation strategies. The South American Gran Chaco is one of the most threatened ecosystems in the Americas. Yet critical data on the population genetic structure for many mammals occupying this ecoregion, including primates such as Azara's owl monkey (Aotus azarae), are lacking. We used 22 microsatellite loci and mitochondrial DNA sequences to assess genetic diversity and population structure in A. azarae, an arboreal, pair-living platyrrhine primate, in the Gran Chaco of northern Argentina in areas characterized by a contiguous gallery forest and patches of forest in naturally occurring savanna. We also analyzed sex-specific patterns of isolation-by-distance and used assignment tests to evaluate dispersal patterns, assess potential sex differences in gene flow, and assessed potential differences in gene flow within and between gallery forest and forest patch habitats. We found limited genetic structure within sampling locations, and a moderate level of genetic differentiation between the two most-distant regions. There was no evidence of genetic differentiation between habitat types (gallery vs. forest patches). Some analyses suggest greater dispersal by females than males, although the evidence is not strong. We integrated these results with previous demographic and behavioral observations gathered since 1996 as part of a long-term study of owl monkeys in this area. This study constitutes an important first step in characterizing the genetic structure and patterns of gene flow for Azara's owl monkey populations in Argentina, which is essential for combatting the effects of habitat loss and fragmentation on these native populations and for informing conservation management strategies for pair-living primates throughout the South American Gran Chaco.