Biology subjects

MacIntosh, A. J. J.

Publications and source records attributed to MacIntosh, A. J. J..

3 recordsLinked to original sources

bioRxiv2026

Oral and gut microbiomes reveal latent physiological constraints on release readiness in rehabilitating Javan slow lorises

Illegal wildlife trade and habitat degradation displace thousands of animals annually in Southeast Asia, with many confiscated primates housed in rehabilitation centers that increasingly function as long-term holding environments. In slow lorises, dental clipping associated with the pet trade may generate persistent disruption along the oral-gut axis, potentially undermining physiological readiness for release in ways not captured by conventional screening. Here, we evaluated whether microbiome structure provides an integrative marker of release readiness in rehabilitating Javan slow lorises (Nycticebus javanicus). From June to October 2024, we collected fecal (n = 26) and saliva (n = 18) samples from 19 adults housed at YIARI, including 10 release candidates and 9 non-candidates classified primarily based on tooth loss, medical history, and possibility of release. Bacterial communities were characterized using 16S rRNA (V3-V4) amplicon sequencing, with alpha and beta diversity, taxonomic enrichment (LEfSe), and predicted functional profiles (PICRUSt2) assessed. Microbiome composition was strongly compartmentalized by body site, with higher alpha diversity in the gut. Release candidacy was associated with modest gut compositional differences, whereas oral microbiomes showed pronounced divergence between candidates and non-candidates. Non-candidates were enriched in dysbiosis-associated taxa and degradation-oriented functional pathways, while candidates showed enrichment of biosynthetic and central energy metabolism pathways. Gut microbiome structure was stable across pre-release and soft-release phases. These findings indicate that oral and gut microbiomes represent distinct physiological niches and that persistent oral microbiome alteration is a sensitive marker of long-term dental perturbation. Integrating microbiome-informed metrics may improve multidimensional assessment of release readiness.

microbiology↗

bioRxiv2025

Dissecting disgust and fear in chimpanzees: From facilitation to disruption of cognitive processes

Disgust and fear are defensive emotions that evolved to address different types of threat. Disgust reduces pathogen exposure through avoidance, whereas fear promotes vigilance and escape from predators. While cognitive mechanisms of fear have been extensively studied, those underlying disgust remain less understood, particularly in nonhuman animals. We examined how cues of disease and predation risk influence cognitive processes in captive chimpanzees (Pan troglodytes). In three touchscreen experiments, subjects performed a number ordering task while exposed to disgust-related images (carcasses, rotten food, disease-associated invertebrates), pathogen-related odors (cadaverine, butyric acid) or fear-related images (snakes). Task performance was assessed via accuracy (proportion of correct trials), reactivity (latency to touch the first numeral), and efficiency (latency to complete trials). We found that disgust cues - particularly those related to body decomposition and food spoilage - modulated task performance in distinct temporal patterns. Carcass images reduced accuracy relative to invertebrate images and slowed performance compared to snake images, while butyric acid - and to a lower extent cadaverine - initially facilitated but later disrupted efficiency upon re-exposure. In contrast, snake images enhanced performance by reducing latencies. To test whether these effects reflected differences in visual attention, we conducted a fourth eye-tracking experiment with new carcass and snake images. Both types of stimuli captured and held attention, partly echoing human data showing sustained attention to snakes but typically not to disgust images. Overall, our results reveal distinct cognitive signatures of disgust and fear in chimpanzees, offering comparative insight into the evolution of defensive emotions. Significance statementDisgust and fear are fundamental emotions that evolved to protect organisms from distinct kinds of threats - disease and predation - but their effects on cognition have rarely been compared, especially in nonhuman animals. In this study, we examined how chimpanzees respond to pathogen-and predator-related cues using touchscreen and eye-tracking experiments. We found that pathogen cues influenced cognitive performance in complex, time-dependent ways, sometimes enhancing and later disrupting it, while predator cues consistently improved performance. Both types of stimuli captured and held attention, although sustained attention to pathogen cues was unexpected. These findings reveal distinct emotional and cognitive signatures of disgust and fear, shedding light on the evolutionary roots of how emotions shape behavior and attention.

animal behavior and cognition↗

bioRxiv2021

Linking Parasitism to Network Centrality and the Impact of Sampling Bias in its Interpretation

AO_SCPLOWBSTRACTC_SCPLOWGroup living is beneficial for individuals, but also comes with costs. One such cost is the increased possibility of pathogen transmission because increased numbers or frequencies of social contacts are often associated with increased parasite abundance or diversity. The social structure of a group or population is paramount to patterns of infection and transmission. Yet, for various reasons, studies investigating the links between sociality and parasitism in animals, especially in primates, have only accounted for parts of the group (e.g., only adults), which is likely to impact the interpretation of results. Here, we investigated the relationship between social network centrality and an estimate of gastrointestinal helminth infection intensity in a whole group of Japanese macaques (Macaca fuscata). We then tested the impact of omitting parts of the group on this relationship. We aimed to test: (1) whether social network centrality - in terms of the number of partners (degree), frequency of interactions (strength), and level of social integration (eigenvector) - was linked to parasite infection intensity (estimated by eggs per gram of faeces, EPG); and, (2) to what extent excluding portions of individuals within the group might influence the observed relationship. We conducted social network analysis on data collected from one group of Japanese macaques over three months on Koshima Island, Japan. We then ran a series of knock-out simulations. General linear mixed models showed that, at the whole-group level, network centrality was positively associated with geohelminth infection intensity. However, in partial networks with only adult females, only juveniles, or random subsets of the group, the strength of this relationship - albeit still generally positive - lost statistical significance. Furthermore, knock-out simulations where individuals were removed but network metrics were retained from the original whole-group network showed that these changes are partly a power issue and partly an effect of sampling the incomplete network. Our study indicates that sampling bias can thus hamper our ability to detect real network effects involving social interaction and parasitism. In addition to supporting earlier results linking geohelminth infection to Japanese macaque social networks, this work introduces important methodological considerations for research into the dynamics of social transmission, with implications for infectious disease epidemiology, population management, and health interventions.

animal behavior and cognition↗