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.