Meeting Abstract
Butterflies are among the most extensively studied insects, and research on their behaviour has contributed to our understanding of animal territoriality, migration, conservation biology and climate change. A full appreciation of an animal’s behaviour includes knowledge of its sensory ecology, and whilst visual, chemical, and tactile senses have been widely studied in butterflies, the auditory system is poorly understood. Recent work from my lab shows that many species of diurnally active butterflies possess tympanal ears on their forewings that are sensitive to low frequency sounds (best sensitivity ~1-6 kHz). Yet, a key question remains unanswered: What is the adaptive significance of their hearing? Most species are diurnally active and do not produce sounds, so bat detection or conspecific communication are unlikely. Birds are a primary predator of butterflies and we pose the hypothesis that butterflies (and other insects) use their ears as ‘bird detectors’. We provide evidence that insectivorous birds produce broadband sounds as byproducts of flight that these sounds overlap with insect hearing. We show that butterfly ears respond neurophysiologically to predator sounds. Additionally, sounds of approaching predators evoke escape responses. Results to date support the hypothesis that the ears of butterflies, like those of many vertebrate prey such as some rabbits and lizards, function in predator risk assessment. We propose that the function of low-frequency hearing for predator risk assessment is underappreciated for both invertebrate and vertebrate prey, and warrants further investigation.
