Defensive tail displays in dice snakes (Natrix tessellata) are influenced by colour morph and sex

Defensive tail displays are common in squamates; however, the factors underlying the occurrence of such displays are rarely studied. We tested 268 adult dice snakes (Natrix tessellata) in a population with three colour morphs, exploring the effects of morph, sex, body size, tail length and temperature on the occurrence of tail waving in two stages of the antipredator response. When captured, the blotched morph tail waved the most, followed by melanistic then green morphs. Males displayed tail waving during post-capture immobility more often than females, possibly due to sexual dimorphism in tail length and/or fleeing speed. The occurrence of tail waving was low in response to a researcher as a “predator” (∼2.6% on capture; ∼6.8% during immobility), however the occurrence of this behaviour during encounters with real predators might be different. Large sample size is crucial for revealing fine scale effects on rare behaviours such as tail waving.