Chemical sensing in vertebrates is crucial in their lives, and efforts are undertaken towards deciphering their chemical language. Volatile organic compounds (VOCs) are a group of chemicals believed to play an essential role in a wide variety of animal interactions. Therefore, understanding what animals sense themselves and untangling the ecological role of their volatile cues can be accomplished by analysing VOC emissions. A proton‐transfer‐reaction time‐of‐flight mass spectrometer (PTR‐TOF‐MS) is an instrument that measures VOCs in real‐time in an air sample. Since this technique acts as a hyper‐sensitive ‘nose’ it has a similar potential in deciphering the chemical language of vertebrates. Here, we validate the use of PTR‐TOF‐MS as a tool to measure VOCs from vertebrates, which in turn will help resolve vertebrate interactions through VOCs. The instrument monitors and records the full spectrum of VOCs emitted by an individual with a high accuracy and low detection limit, including transient VOC emissions. We propose and test diverse measuring configurations that allow for measurement of VOC emissions from different vertebrates and their exudates: full body, specific parts of the body, urine and femoral pores. In addition, we test configurations for sudden and short‐lasting processes as VOCs emitted during adder skin shedding as well as the emissions of skin secretions upon mechanical and physiological stimulation in amphibia. Our configurations work in tandem with gas chromatography–mass spectrometry (GC‐MS) to allow compound structure verification. We discuss the configurations and methodologies used and conclude with recommendations for further studies, such as the choice of chamber size and flow. We also report the results of the measurements on vertebrates—that are novel to science—and discuss their ecological meaning. We argue that PTR‐TOF‐MS has a high potential to resolve important unanswered questions in vertebrate chemical ecology with great adaptability to a wide range of experimental set‐ups. If combined with a structure verification tool, such as GC‐MS, the creative deployment of PTR‐TOF‐MS in various future study designs will lead to the identification of ecologically relevant VOCs.

Lacertid lizards use chemical cues emitted by saurophagous snakes to evade predation. Whether these lizards can detect and respond to the chemical cues of predatory mammals has not been studied. As many mammals carry distinct body odours and/or use chemical cues for intraspecific communication, lizards can be expected to use these chemicals as early warning cues. To test this idea, we observed the behaviour of Asian grass lizards (Takydromus sexlineatus) that had been transferred to an unfamiliar test arena containing one of four scent treatments. No particular scent was applied to the arena in the control situation. Diluted aftershave served as a pungency control. In the snake treatment, scent of the Oriental whip snake (Ahaetulla prasina) was applied. We included this treatment to learn how Asian grass lizards react to predator chemical cues. Finally, in the mongoose treatment, the lizards were confronted with scent cues of several small Indian mongooses (Herpestes auropunctatus). Snake scent elicited foot shakes, startles and tail vibrations. These are behaviours that in lacertid lizards are associated with stressful situations such as predatory encounters. Surprisingly, lizards confronted with mongoose scent exhibited none of these stress‐indicating behaviours. In fact, their behaviour did not differ from that of lizards subjected to an odourless control treatment. These results raise concern. Mongooses are rapidly invading ecosystems worldwide. If lizards that have co‐evolved with mongooses are unable to detect these predators’ presence through chemical cues, it seems highly unlikely that evolutionary naïve lizards will develop this ability rapidly.

Newly introduced predators constitute a major threat to prey populations worldwide. Insular prey animals in particular often do not succeed in overcoming their naivety towards alien predators, making them specifically vulnerable. Why this is the case remains incompletely understood. Here, we investigate how the ability to detect and respond to predator chemical cues varies among populations of the Dalmatian wall lizard, Podarcis melisellensis. Lizards were sampled from five locations in south-eastern Croatia (one mainland location and four islands) that varied in the composition of their predator community. We observed the lizards’ behaviour in response to chemical cues of native saurophagous snakes (the Balkan whip snake, Hierophis gemonensis, and eastern Montpellier snake, Malpolon insignitus) and an introduced mammalian predator (the small Indian mongoose, Herpestes auropunctatus – a species held responsible for the loss of numerous insular reptile populations worldwide). Mainland lizards showed elevated tongue-flick rates (indicative of scent detection) as well as behaviours associated with distress in response to scents of both native and introduced predators. In sharp contrast, island lizards did not alter their behaviour when confronted with any of the predator cues. Alarmingly, even lizards from islands with native predators (both snakes and mammals) and from an island on which mongooses were introduced during the 1920s were non-responsive. This suggests that insular populations are chemosensorily deprived. As failure at the predator-detection level is often seen as the most damaging form of naivety, these results provide further insight into the mechanisms that render insular-living animals vulnerable to invasive species.

Herbivory is a major factor affecting both the performance and the fitness of the species composing a plant community and, ultimately, conditioning its temporal and spatial dynamics. Coastal dunes are a typical example of primary succession where different biotic and abiotic factors determine plant species occurrence; however, the effect of insect herbivory herein has remained little explored. To address this matter, we combined an observational study along a successional gradient with a greenhouse experiment to determine the occurrence and the impact of plant-aphid interactions. We focused on the species Schizaphis rufula, a widespread and abundant aphid associated with dune grasses in early stages of primary succession in Europe. Firstly, we studied aphid infestation rates on the dune grass Ammophila arenaria along a succession gradient in three locations of the North Sea coast to address the relationship between plant community composition and aphid occurrence; secondly, we tested the effect of aphid herbivory on a set of dune species typical for the different stages of succession. We found that the degree of aphid infestation was inversely correlated with the degree of dune fixation. The results of the experiment showed that aphid multiplication was significantly higher and its effect more pronounced on two early successional grass species, i.e. A. arenaria and Leymus arenarius. Here aphid multiplication resulted in a severe decrease in plant biomass; in late successional grass species, there was limited multiplication and no effect on biomass. The results of the field survey and the greenhouse experiment indicate that aphids show a clear preference for plants from early successional stages and, moreover, they have a greater impact on these plant species. All this supports the hypothesis of aphid herbivory as a driving factor of primary succession in coastal dunes.