Efficacy of multiple defences of mimics from the golden mimicry complex against two predators

Many prey species employ multiple defences during interactions with predators. Multiple defences can provide a selective advantage against a single predator at different stages of the interaction or attack, as well as against multiple predator types. However, the efficacy of multiple defences both during different sequences of an attack and against multiple predator types, remains poorly understood. We measured and classified defensive traits used by five mimics (Müllerian and Batesian) of the myrmecomorphic golden mimicry complex and one non-mimetic species. We then performed predatory trials using two different predators that differed markedly in their body size, trophic specialisation, and how they handle prey – one being an ant specialist (spider) and the other a generalist which avoided ants (skink). We identified 12 defensive traits and classified them into four groups (primary, chemical, mechanical, behavioural), which were strongly correlated. Skinks were much less likely to attack and capture mimics than the ant-eating spider predators. Our results show that multiple defences (five or six) were used against each predator. The defensive behaviours and features that were most effective against skinks included appendage waving and large body size, whereas the golden ‘shine’ warning signal, large body size, cuticle thickness, and defensive gland size were most effective against spiders. Most defences appeared to be predator-specific. We conclude that potential prey in the golden mimicry complex have been selected for multiple defences because of their vulnerability to different predator types and consequently, the efficacy of some of these defences likely represents a trade-off.

Methods
The details are described in the Methods of the article.