First report of Dipetalonema gracile in a captive Marcgrave’s capuchin monkey (Sapajus flavius) in northeastern Brazil: Scientific communication

Parasitic infections are important concern to the Wildlife Conservation Biology, particularly in endangered species. Herein, we report a parasitism by Dipetalonema gracile Rudolphi, 1809 (Spirurida, Filarioidea, Onchocercidae), in the peritoneal cavity of a captive Marcgrave’s capuchin monkey (Sapajus flavius) that died at the Wild Animal Screening Center (CETAS) of the Brazilian Institute for the Environment and Renewable Natural Resources (IBAMA) in the municipality of Cabedelo, state of Paraíba, northeastern Brazil. The necropsy revealed two filarial worms D. gracile in the abdominal cavity. Exudates, thin fibrin layers and fibrous adhesions were also present in the mesentery and spleen capsule. The mesenteric, mandibular, and tracheobronchial lymph nodes were enlarged. Multiple small nodules were seen in the spleen parenchyma. Microscopic examination of the lymph nodes and spleen revealed markedly and diffuse inflammatory reaction, with edema, plasma cells, eosinophils, histiocytes, lymphocytes and rare multinuclear giant cells, with obliteration of the normal histological architecture of the organ. This is the first report of D. gracile parasitism in Marcgrave’s capuchin monkeys, a critically endangered species. Studies of this nature significantly contribute to the knowledge of the parasitic fauna of endangered species, in addition to helping to formulate conservation strategies (in situ and ex situ) and records of new hosts and new areas of occurrence of parasites.

Observer effects in a remote population of large-headed capuchins, Sapajus macrocephalus

Human observers often are present when researchers record animal behavior, which can create observer effects. These effects are rarely explicitly investigated, often due to the assumption that the study animal is habituated to or unaffected by a human’s presence. We investigated the effect of human pressure gradients on a remote population of large-headed capuchins, Sapajus macrocephalus, looking specifically at the effects of number of observers, distance to observers, and distance to the research base. We conducted this study over 4 months in the Pacaya-Samiria Nature Reserve, Peru, and collected 199 two-minute focal samples of capuchin behavior. We found that capuchin monkeys fed less when human observers were closer to the focal individual, when more observers were present, and when capuchins were closer to the research base. We found no other consistent differences in capuchin monkey behavior across the measured human pressure gradients, although capuchins directed a high proportion of their vigilance toward humans (29% in adults and 47% in infants). Our results support the hypothesis that human pressure gradients influence animal behavior. Given the proportion of human directed vigilance, we recommend that all studies that use human observers to record animal behavior consider human-directed vigilance, record the number of observers, as well as the observer-focal animal distance, to check for these effects.

Visual discrimination of primate species based on faces in chimpanzees

Many primate studies have investigated discrimination of individual faces within the same species. However, few studies have looked at discrimination between primate species faces at the categorical level. This study systematically examined the factors important for visual discrimination between primate species faces in chimpanzees, including: colour, orientation, familiarity and perceptual similarity. Five adult female chimpanzees were tested on their ability to discriminate identical and categorical (non-identical) images of different primate species faces in a series of touchscreen matching-to-sample experiments. Discrimination performance for chimpanzee, gorilla and orangutan faces was better in colour than in greyscale. An inversion effect was also found, with higher accuracy for upright than inverted faces. Discrimination performance for unfamiliar (baboon and capuchin monkey) and highly familiar (chimpanzee and human) but perceptually different species was equally high. After excluding effects of colour and familiarity, difficulty in discriminating between different species faces can be best explained by their perceptual similarity to each other. Categorical discrimination performance for unfamiliar, perceptually similar faces (gorilla and orangutan) was significantly worse than unfamiliar, perceptually different faces (baboon and capuchin monkey). Moreover, Multidimensional Scaling analysis of the image similarity data based on local feature matching revealed greater similarity between chimpanzee, gorilla and orangutan faces than between human, baboon and capuchin monkey faces. We conclude our chimpanzees appear to perceive similarity in primate faces in a similar way to humans. Information about perceptual similarity is likely prioritised over the potential influence of previous experience or a conceptual representation of species for categorical discrimination between species faces.

Eye preferences in capuchin monkeys (Sapajus apella)

This study explored whether capuchin monkey eye preferences differ systematically in response to stimuli of positive and negative valence. The ‘valence hypothesis’ proposes that the right hemisphere is more dominant for negative emotional processing and the left hemisphere is more dominant for positive emotional processing. Visual information from each eye is thought to be transferred faster to and primarily processed by the contra-lateral cerebral hemisphere. Therefore, it was predicted capuchin monkeys would show greater left eye use for looking at negative stimuli and greater right eye use for looking at positive stimuli. Eleven captive capuchin monkeys were presented with four images of different emotional valence (an egg and capuchin monkey raised eyebrow face were categorised as positive, and a harpy eagle face and capuchin monkey threat face were categorised as negative) and social relevance (consisting of capuchin monkey faces or not), and eye preferences for viewing the stimuli through a monocular viewing hole were recorded. While strong preferences for using either the left or right eye were found for most individuals, there was no consensus at the population-level. Furthermore, the direction of looking, number of looks and duration of looks did not differ significantly with the emotional valence of the stimuli. These results are inconsistent with the main hypotheses about the relationship between eye preferences and processing of emotional stimuli. However, the monkeys did show significantly more arousal behaviours (vocalisation, door-touching, self-scratching and hand-rubbing) when viewing the negatively valenced stimuli than the positively valenced stimuli, indicating that the stimuli were emotionally salient. These findings do not provide evidence for a relationship between eye preferences and functional hemispheric specialisations, as often proposed in humans. Additional comparative studies are required to better understand the phylogeny of lateral biases, particularly in relation to emotional valence.

DENSIDADE POPULACIONAL E ANÁLISE COMPORTAMENTAL DE CEBUS APELLA NA MATA DOS MACACOS ANTES E DURANTE PANDEMIA DA COVID-19

A pesquisa teve como objetivo acompanhar as mudanças populacionais e comportamentais da população de Cebus apella que vive na Mata dos Macacos em Santa Fé Do Sul/SP e investigar mudanças que afetaram direta ou indiretamente a população de macaco prego no período anterior e durante a pandemia da Covid-19. A mata é um local turístico onde os animais têm contato direto com os turistas e têm alimentação livre de acordo com o que os visitantes oferecem. Com a pandemia e, consequentemente, o fechamento do local, observaram-se mudanças na população, que mostrou comportamentos, tamanho da população e interação com os humanos alterados. Com as visitas de antes e durante a pandemia, foram registradas todas as alterações observadas de acordo com a situação que a mata vivenciou. Os macacos que, anteriormente, tinham visitas frequentes e comida à vontade, com a pandemia, tiveram a situação transformada, forçando-os a voltarem a ter seus comportamentos mais naturais, buscando seu alimento e sem ligação com turistas. POPULATION DENSITY AND BEHAVIORAL ANALYSIS OF CEBUS APELLA AT MATA DOS MACACOS BEFORE AND DURING COVID-19 PANDEMIC ABSTRACT The research aimed at monitoring population and behavioral changes of Cebus paella population living in Mata dos Macacos in Santa Fé do Sul, as well as investigating changes that directly or indirectly affected the capuchin monkey population in the period before and during Covid-19 pandemic. The woods are a tourist place where animals are in direct contact with tourists who feed them freely. With the pandemic, and consequently the local lockdown, it was possible to identify some changes in the troop, where behavior, population size, and interaction with humans were changed. With the visits before and during the pandemic, all the changes observed were reported accordingly the situation experienced in the woods. The monkeys that were previously visited and were freely fed, due to de pandemic, had their situation changed and they were forced to switch back to their natural behavior, hunting for their food with no connections with tourists. Descriptors: Cebus apella. Behavior, Visits.

Capuchin monkey rituals: an interdisciplinary study of form and function

Many white-faced capuchin monkey dyads in Lomas Barbudal, Costa Rica, practise idiosyncratic interaction sequences that are not part of the species-typical behavioural repertoire. These interactions often include uncomfortable or risky elements. These interactions exhibit the following characteristics commonly featured in definitions of rituals in humans: (i) they involve an unusual intensity of focus on the partner, (ii) the behaviours have no immediate utilitarian purpose, (iii) they sometimes involve ‘sacred objects’, (iv) the distribution of these behaviours suggests that they are invented and spread via social learning, and (v) many behaviours in these rituals are repurposed from other behavioural domains (e.g. extractive foraging). However, in contrast with some definitions of ritual, capuchin rituals are not overly rigid in their form, nor do the sequences have specific opening and closing actions. In our 9260 h of observation, ritual performance rate was uncorrelated with amount of time dyads spent in proximity but (modestly) associated with higher relationship quality and rate of coalition formation across dyads. Our results suggest that capuchin rituals serve a bond-testing rather than a bond-strengthening function. Ritual interactions are exclusively dyadic, and between-dyad consistency in form is low, casting doubt on the alternative hypothesis that they enhance group-wide solidarity. This article is part of the theme issue ‘Ritual renaissance: new insights into the most human of behaviours’.