Pilot Study on Odour Source Preference from “Group and kin recognition via olfactory cues in chimpanzees (Pan troglodytes)” from Group and kin recognition via olfactory cues in chimpanzees (Pan troglodytes)

We conducted a pilot study to test which odour source chimpanzees respond most strongly to by presenting three different odour sources (body odour, faeces and urine) of the same individual (a group member) to two groups of chimpanzees at Leipzig Zoo using the same setup as for the ingroup vs. outgroup bioassay. We found that the effect of odour source was significant for sniffing and nose within 20 cm, and the interaction between odour source and sex was significant for manipulating. Pairwise post-hoc comparisons revealed that subjects sniffed significantly longer at urine as compared to faeces (Estimate=0.829, SE=0.225, z=3.691, p=0.001) and body odour (Estimate=0.577, SE=0.222, z=2.604, p=0.050) and that they placed their nose significantly longer within 20 cm of urine than faeces (Estimate=1.002, SE=0.314, z=3.197, p=0.008). Thus, we used urine as odour source for subsequent bioassays. The increased inspection time of urine compared to faeces might reflect a trade-off between gathering information about the scent donor and infection risk from faeces.