Anti-predator behavior by a nesting hummingbird in response to a caterpillar with eyespots.

Caterpillars and adults of a variety of butterflies and moths have eye-like spots (Janzen et al. 2010) that deter potential predators (Stevens et al. 2007, Blut et al. 2012, Hossie and Sherratt 2013) or deflect attacks to less-vital body parts (Vallin et al. 2011). Observations of how eyespots affect animal interactions in natural settings are extremely rare, and although experimental studies have consistently shown anti-predator effects, it remains uncertain if eyes cause mistaken identity of a dangerous animal or function by other mechanisms not involving mistaken perception of eyes (Stevens and Ruxton 2014). Here we report a naturally occurring series of events in which a nesting hummingbird displayed highly replicable and stereotypical anti-snake behavior (Fig 1) in response to a caterpillar whose eyespots resemble (Fig 2b,c) a co-occurring arboreal snake that preys on nestling birds (Fig 2d,e). This article is protected by copyright. All rights reserved.