The alcohol dehydrogenase (ADH) gene family is widespread throughout the animal kingdom and plays a crucial role in oxidizing different types of alcohol. In mammals, this gene family has undergone multiple duplications, resulting in a group of genes that can be classified into six classes. Class I ADH duplication is characteristic of primates and the enzyme can work not only as a homodimer but also as a heterodimer. Therefore, having more class I ADH genes possibly lead to forming variable dimers which contribute to a variety of kinds or concentration of alcohol oxidization. Some previous studies hypothesized that class I gene evolution might be related to the adaptation of fermented fruit eating because the genes mainly play a role in ethanol digestion in the human liver. Although such studies have shown that the copy number varied between primate species, there are very few studies showing the phylogenetic relationship of the duplicated genes that must give a good hint of adaptive evolution. We assessed the number of class I ADH genes in primates using blast+, constructed the phylogenetic tree, and translated the genes in silico to estimate the number of pseudogenes. Our results suggest that the phylogenetic topology was coincident with the previous reports in that genes formed a clade respectively in the infraorder level. Notably, we found that the gene loss occurred in langurs and pseudogenization occurred in tarsiers and red slender loris, suggesting that alcohol metabolization might not be as important for folivores and insectivores as it is for frugivores.

Coat coloration is one of greatest diverse phenotype in primates. The trait is often under selection because even small change in coloration can cause significant implication in camouflage, heat absorption, and communication. One notable form of coloration is melanism, which is a genetic trait that results in increased pigmentation and a darker coloration. Sulawesi macaques, seven endemic species located in Sulawesi Island, have rapidly speciated from the common ancestor and morphologically diversified. Distinct from other macaques, they exhibited distinct dark coat color but with difference in darkness and pattern between species. To understand the genetic mechanism of melanism variation, we firstly focus on both sequence and functional variation of MC1R, a gene regulating melanin synthesis and density. In total, we determined MC1R sequence of 46 saliva samples of five species of Sulawesi macaques, respectively. We found each species exhibited fixed amino acid substitutions. We further studied the cAMP induced ability of the MC1R in vitro. Each species MC1R exhibited specific functional performance, most of them have decreased MC1R basal activity but lead by different key residues, respectively. Further, we collected hair follicles from black and white body part of individual and determined RNA expression pattern. We found black samples has more similar expression pattern which are clustered in PCA analysis. While white samples showed large variation. Further analysis on expression pattern between black and white body part will promote the understanding of melanism variation.

Tourism can play a significant role in the conservation of mountain gorillas (Gorilla beringei beringei) by financing the protection of their habitat, but few systematic studies have focused on the impacts of tourist presence on gorilla behavior. We assessed stress-coping mechanisms (prosocial behaviors), behavioral indicators of stress (self-scratching), direct interactions with humans (agonistic, neutral and avoidance behaviors), and changes in social cohesion patterns (time spent with and number of individuals in close association), in the presence and absence of tourist groups visiting one group of mountain gorillas living in Bwindi Impenetrable National Park, Uganda. Generalized linear mixed models and social network analysis were used to analyse differences in gorilla behavior as a function of (a) presence vs. absence of tourists and (b) proximity to tourists (<3 m vs >3 m). Contrary to guidelines, tourists spent 60% of their viewing time within 3 m of the gorillas. During tourist visits, gorillas increased time spent in prosocial behavior and rates of self-scratching and human-directed behavior, increasing also social cohesion. When tourists approached gorillas within 3 m, prosocial behavior, human-directed behavior, and social cohesion increased, but only adult males increased self-scratching rates. We conclude that tourists are influencing gorilla behavior and we recommend following and enforcing the IUCN guidelines by keeping a minimum 7 m distance when viewing gorillas.

Studies of captive chimpanzees have revealed six latent variables (factors) account for individual variation in large numbers of traits. These factors include Dominance, and five further factors—Extraversion, Conscientiousness, Agreeableness, Neuroticism, and Openness—that resemble personality factors found in human societies. A study of personality among chimpanzees who lived or were living in Gombe National Park, Tanzania, however, did not find these factors. One possible explanation for this finding was that, by necessity, a brief version of the Hominoid Personality Questionnaire was used. The present study tested this possibility in 40 chimpanzees in Budongo Park, Uganda. These chimpanzees belonged to either the Sonso or Waibira community. Seven field workers and researchers provided ratings using the Hominoid Personality Questionnaire (HPQ) such that each chimpanzee was rated by an average of 3.875 raters. A total of 46 of the 54 items showed evidence of interrater reliability. We used a regularized exploratory factor analysis to extract factors from 39 items (the maximum possible for the sample size). These factors were identifiable as those found in other studies of chimpanzees. These preliminary findings are consistent with studies that suggest that the six personality factors identified in captive samples are variants of the essential traits of chimpanzees.

We investigated whether Japanese macaques possess metacognitive abilities by conducting experiments from 2021 to 2022 on a group of ten free-ranging macaques inhabiting Awaji Island. The macaques were tested on a task where they had to find food hidden in one of four tubes. We observed whether they would look inside the tubes before making a choice when they did not know which tube contained food. We also varied the cost of looking and the quality of the food reward. Our findings revealed that most of the macaques looked inside the tubes more frequently when they did not know the food's location. Some macaques tended to reduce their looks when the cost of looking was high, but only when they already knew where the food was. When a high-quality reward was at stake, a few macaques tended to look inside the tubes more frequently, even when they already knew the food’s location. These results suggest that Japanese macaques adjust their information-seeking behavior based on their level of knowledge, the cost associated with seeking information, and the potential value of the reward.

While infant handling has been reported in primate species, little has been reported about the infants’ reactions to handling. Here, we present a field study of infant handling and infants’ reactions after being handled in Japanese macaques in Yakushima (Macaca fuscata yakui). We tracked 12 infants born in a large macaque group for a year after the birth of each infant and continuously recorded the time and type of infant handling and the infant’s reaction. We found that infants showed certain patterns in their reactions to handling they were targeted for: infants showed quicker reactions to certain types of handling. Some types of the reaction occurred soon after handling, while others occurred more slowly. Long-lasting handling sometimes made infants squeak, even if it was not rough. We also found that vocal responses were the most effective in attracting mothers’ attention. These findings indicate that infants’ behaviors toward handling may have different meanings; infants may express their own conditions that vary depending on the different handling situations they are involved in. As an attempt to highlight infants’ autonomy, this study suggests paying attention to infants even in infant-directed behaviors.