Common Scents? A review of potentially shared chemical signals in the Order Carnivora.

Many animals transmit information in the form of chemical signals to modify behaviour or induce physiological change in receivers. For some taxa, such as species in the order Carnivora, chemical signals are known to provide a critical mode of communication, although they are still poorly understood compared to other signal modalities. Here, we review the literature to identify and categorise potential chemical signals within the Carnivora with a view to determining commonalities based on sex, taxon, and function. Data were drawn from 112 publications, dating from 1896-2021. Of the 1,532 discrete chemicals identified, 169 were detected in >5 species, with 58 found in ≥10 species. However, multiple different names were often used to report the same compound, reducing the transparency of the literature. 252 chemicals were identified as biomarkers, i.e., associated with specific behavioural contexts (dominance hierarchy, appeasement, agonistic, etc.) or specific demographic traits (age, sex, etc.). Few studies established a causal link between these biomarkers and behavioural or physiological changes, so only a few could be definitively described as behaviourally functional bioactive signals. We found high variability concerning which species, chemicals, and sources were represented in the literature, which could potentially lead to a perceptual bias in the relative importance of certain chemicals. Finally, we propose a method for standardised reporting of chemical signals and suggest that future work should focus on more consistent expansion of the range of species, products, and chemical types analysed, so that the phylogenetic relationship of chemical signals across taxa can be determined.