Theatrical frogs and crafty snakes: predation of visually-signalling frogs by tail-luring and ambushing pitvipers
aqua, International Journal of Ichthyology, pp. 117-124, Volume 11, Issue 3 – September 2006
A species of torrent frog (Hylodes asper) is a common prey to two species of pit viper (Bothrops jararacussu and B. jararaca) in coastal streams of the Atlantic forest in south-east Brazil. The diurnally active frogs are cryptically coloured against the rocky background and the males advertise their presence with visual signals. When a displaying male extends and moves a hind limb, the whitish digits and toe fringes stand out against the background. Moreover, the frogs have acute vision and are able to spot a moving prey at up to 2.8 m. The pit vipers are habitually nocturnal; nonetheless juveniles of the two species forage for frogs by day on the stream banks. The frogs are ambushed or lured by wiggling movements of the tail used by the pit vipers to attract ectothermic prey. Juvenile pit vipers often have whitish or yellowish tail tips that stand out against their camouflage colours while coiled up in ambush. I suggest that the pit vipers’ tactic of luring with the tail benefits from the visual signalling used by the frogs, since the frogs tend to react to the movement of light-coloured extremities. Similar prey-predator relationships may occur on tropical streams that harbour visual-signalling diurnal frogs and vipers that forage for frogs and lure them with coloured tail tips.
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