Prey often adopt antipredator strategies to reduce the likelihood of predation. In the presence of predators prey may use antipredator strategies that are effective against a single predator (specific) or that are effective against several predators (nonspecific). Most studies of predator avoidance behaviours have focussed on single-predator systems, despite the fact that prey often are confronted with predator rich environments. However, when more than one predator is present, specific antipredator behaviours can conflict and avoidance of one predator may increase vulnerability to another. In the presence of more than one predator, prey may have to either choose between avoiding one predator over another or adopt a different non-specific strategy to reduce overall risk. Using the mountain log skink I consider how individuals cope with multiple predators.
In one study I recorded the behaviours of lizards responding to the nonlethal cues of a bird and snake presented singly and simultaneously. Lizards use specific and conflicting antipredator tactics when confronted with each predator as evidenced by refuge use. However when both predators were present, lizards refuge use was the same as in the predator free environment, indicating that they abandoned refuge use as a primary mechanism for predator avoidance. In the presence of both predators they reduced their overall movement and time spent thermoregulating. This shift in behaviour may represent a compromise to minimize overall risk following a change in predator exposure. This provides evidence of plasticity in lizard antipredator behaviour and shows that prey responses to two predators cannot be accurately predicted from what is observed when only one predator is present.
In another study I investigated if skinks showed preferential avoidance of snake odours based on the relative predation risk posed by different snake species. This relative predation risk was estimated using information on density, diet specificity and foraging habit of each snake species. I tested retreat-site selection in two-choice tests, where lizards chose between different combinations of control and snake treated retreat-sites as well as two retreat-sites treated with different snake species odours. Lizards preferred control-treated retreat-sites to those treated with snake odours and showed a differential avoidance response to refuges treated with odours from different snake species. There was strong evidence to suggest that lizards preferentially avoided refuges with the odours of the snake that posed the greatest predation risk, the white-lipped snake (Drysdalia coronoides). Naïve juvenile lizards were also tested and their response was similar to the adults demonstrating that the behaviour is innate and not the result of higher encounter rates of more common snake odours. To my knowledge this is one of the first studies to demonstrate that prey can prioritise avoidance to a single most dangerous predator in the face of several predators and conflicting avoidance responses.
Stapley J. 2004. Do mountain log skinks (Pseudemoia entrecasteauxii) modify their behaviour in the presence of two predators, Behavioral Ecology and Sociobiology 56:185-189.
Stapley J. 2003. Differential avoidance of snake odours by a lizard: evidence for prioritised avoidance based on risk, Ethology 109:785-796.