Don't You Know That I'm Toxic? Wild Birds Learn to Avoid a Novel Aposematic Warning Signal

Many prey species defend themselves against predators by sequestering toxins, which they advertise using conspicuous warning signals—a survival strategy termed ‘aposematism’. It is common for predators to avoid attacking aposematic prey for this reason, however, neophobia towards novel prey items may also play a part in this decision. In this study, we deployed green (cryptic‐morph) and black‐and‐yellow (aposematic‐morph) pastry caterpillar models at a study site in the UK. All models were initially palatable; however black‐and‐yellow models were manipulated with quinine in later trials to be distasteful. When both model colours were palatable, predation increased steadily but neither model type showed a survival advantage over the other. In later trials, black‐and‐yellow models defended with quinine experienced lower predation rates than palatable green models. Predator foraging strategies and implications for the effectiveness of aposematism as a survival strategy are discussed. Other potential explainers for the predation rates observed, such as dietary conservatism and the arrival of juveniles, are also highlighted.