Stress in primates is commonly assessed by observing behavior and measuring
physiological indicators such as fecal cortisol levels. Elevated stress is linked to heightened
self-directed behaviors (SDBs), such as increased self-scratching, along with elevated
circulating cortisol. Yet, for numerous primate species, our understanding of stress
remains limited, particularly regarding lesser-explored biological markers like variation in
stress-related genes and distinctive gut microbial signatures. Here, we report on stress
biometrics in a large population of zoo-housed bonobos (Pan paniscus). We collected
behavior, fecal and DNA samples for 70 adult bonobos housed in 6 European zoological
institutes. We initially quantified the distinct types of self-directed behaviors (SDB) that
increase following a social stressor, specifically an aggressive interaction. The results
revealed a significant increase solely in rough self-scratching, with no notable changes
observed in other self-directed behaviors like gentle self-scratching, nose wiping, and
autogrooming. Next, we assessed gut microbial composition from fecal samples using 16S
rRNA sequencing. Bonobos with elevated levels of rough self-scratching showed lower gut
microbial alpha diversity and alterations in its composition. In the last phase, we will
assess individual genotypes for four serotonergic genes linked to stress-susceptibility in
other species (namely, HTR1A, SLC6A4 and TPH1/TPH2) and explore the degree of
alignment with behavioral and gut microbial stress markers.