Animals have evolved different defensive strategies to survive predation, among which chemical defences are particularly widespread and diverse. Here we investigate the function of chemical defence diversity, hypothesising that such diversity has evolved as a response to multiple enemies. The aposematic wood tiger moth (Arctia plantaginis) displays conspicuous hindwing colouration and secretes two distinct defensive fluids, from their thoracic glands and abdomen. We presented fluids from lab-reared moths to two biologically relevant predators, birds and ants, and measured their reaction in controlled bioassays (no information on colour was provided). We found that defensive fluids are target-specific: thoracic fluids, and particularly the 2-sec-butyl-3-methoxypyrazine (SBMP) which they contain, deterred birds, but caused no aversive response in ants. In contrast, abdominal fluids were particularly deterrent to ants, while birds did not find them repellent. Our study is the first to show evidence of a single species producing separate chemical defences targeted to different predator types, highlighting the importance of taking into account complex predator communities in studies on the evolution of prey defence diversity.

antdataDataset from the bioassay in which ants responded to the defensive fluids of the wood tiger mothbluetitsdataDataset from the bioassay in which blue tits responded to the defensive fluids of the wood tiger moth