Abstract
There is mounting evidence that single compounds can act as signals and cues for mammals and that when presented at their optimal concentration they can elicit behavioural responses that replicate those recorded for complex mixtures like gland secretions and foods. We designed a rapid bioassay to present nine compounds that we had previously identified in foods, each at seven different concentrations (63 treatments), to wild, free-ranging rats and scored each treatment for attraction and three behavioural responses. Nine treatments (taken from five compounds) statistically outperformed the current standard rat attractant, peanut butter. Attraction to treatments was highest at the two lowest concentrations (0.1 and 0.01 μg g−1) and a statistically significant relationship of increasing attraction with decreasing treatment concentration was identified. Our study identified five compounds not previously associated with behavioural responses by rats that elicit equivalent or more intense behavioural responses than those obtained with peanut butter. Moreover, attraction to treatments was driven by a concentration-dependent relationship not previously reported. This is the first study to identify isopentanol, 1-hexanol, acetoin, isobutyl acetate and 2-methylbutyl acetate as possible semiochemicals/cues for rats. More broadly, our findings provide important guidance to researchers in the ongoing search for mammalian semiochemicals and cues.
Highlights
There is mounting evidence that single compounds can act as signals and cues for mammals and that when presented at their optimal concentration they can elicit behavioural responses that replicate those recorded for complex mixtures like gland secretions and foods
Our study demonstrates that wild, free-ranging rats can detect and respond to a suite of different single compounds, and that when the compounds are presented at optimal concentrations they can elicit levels of behavioural responses that outperform a complex mixture like peanut butter
This strongly suggests that isopentanol, 1-hexanol, acetoin, isobutyl acetate and 2-methylbutyl acetate may be important communicatory signals or cues for rats
Summary
There is mounting evidence that single compounds can act as signals and cues for mammals and that when presented at their optimal concentration they can elicit behavioural responses that replicate those recorded for complex mixtures like gland secretions and foods. The mechanisms by which odours induce innate behavioural responses in mammals remains largely unknown[6] and to-date only a small number of mammalian semiochemicals (a chemical substance that transmits a signal) have been formally characterised[7] Odouriforous products, be they urine, faeces, gland secretions, body odours, and foods, are complex natural mixtures. Studies investigating olfactory-mediated behavioural responses to semiochemicals and cues are almost exclusively performed using laboratory-bred animals (e.g., Wistar rats or house mice) or captive animals held in pens, not free-ranging wild animals. This has important implications as the www.nature.com/scientificreports/. Replication at the multi-population (site) scale is possible compared with finite captive (pen or laboratory) animals, allowing for broader, species-level inferences[24,25]
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