State-dependent and risk-sensitive escape decisions in a fossorial reptile, the amphisbaenian Blanus cinereus

Morphological adaptations of amphisbaenians to fossorial life may affect th eir anti-predator behaviour and escape decisions. Amphisbaenians exposed on the soil surface by a predator may decide to escape either by burrowing im mediately or by using alternative defensive behaviours. This decision may d epend on the internal state (body temperature and associated burrowing perf ormance) but, because anti-predator behaviours may be costly, an optimal re sponse should also be sensitive to risk and vary according to the threat of predator attack. In a laboratory experiment we simulated predatory attack on individual amphisbaenians of the species Blanus cinereus, and specifical ly examined the effects of temperature (warm vs, cold) and predation threat (low vs. high) on escape decisions. Amphisbaenians showed significantly lo nger episodes of an alternative anti-predator behaviour on the soil surface (coiling) when the predation threat was high and when the temperature was low. The time to burrow until half of the body was buried was significantly longer when the temperature was low and was significantly shorter when the threat was high. The variations observed in anti-predator behaviours may r eflect the choice of the optimal response under each circumstance, taking i nto account the estimated predation risk, which is dependent on the charact eristics of the initial attack, and potential burrowing performance, which is dependent on body temperature.