Cracking the chemical code: European common lizards (Zootoca vivipara) respond to an hexane soluble predator kairomone

Abstract

In many animals, chemosensation acts as a first line of defence against snake predators. However, in spite of their obvious importance, the chemical nature of cues used by prey to detect snakes remains to be discovered. Here, we analyse which neutral lipids, extracted with n-hexane, are present in the skin of the European adder (Vipera berus) using Gas Chromatography – Mass Spectrometry. The analyses revealed that the washes held a complex cocktail of chemical compounds, with a total of 165 different molecules, mostly steroids (82% of the total ion current) and alkanes (13%), and smaller amounts of carboxylic acids, wax esters, ketones, amides and alcohols. Using bio-assays in which we confronted individuals of a prey species (the European common lizard, Zootoca vivipara) with these washes, we were able to confirm that the kairomones can be extracted using n-hexane. In fact, lizards did not respond to chemical cues still present in adder skin after washing, indicating that the kairomones are indeed strongly n-hexane soluble. Consequently, we have set a next step in deciphering the chemical nature of the predator-prey interaction between the European adder and the European common lizard. We hope our results facilitate further investigation into the chemical ecology of snakes and their prey.