Nocturnal shift in the antipredator response to predator-diet cues in laboratory and field trials

Prey species may react to predator chemical traces in the environment with a variety of antipredator behaviors (Weldon, 1990; Chivers and Smith, 1998; Kats and Dill, 1998). Such responses to predator chemical cues might reduce predation risk, but also may result in lost foraging or mating opportunities (Lima, 1998a,b), so it is not surprising that some species adjust their responses based on the degree of perceived predation threat. These modifications may be based on chemical information gathered directly from the predator or its recent prey (Madison et al., 1999a; Chivers and Mirza, 2001). The mosaic of chemical products released at a predation site, and dispersed by the predator, could allow nearby prey to assess predation threat and fine-tune their responses. Among the chemical cues released from predators during and after a predation event, those associated with predator diet have emerged as an important factor in predator assessment by both aquatic (Chivers and Mirza, 2001) and terrestrial prey species (Madison et al., 1999a,b). However, in most circumstances it is unclear whether the active components of the cue are from the prey, the predator, or some combination of prey and predator cues (e.g., Madison et al, 2002). As one example of this complexity, the interaction between the terrestrial red-backed salamander, Plethodon cinereus, and its garter snake predator, Thamnophis sirtalis, shows that during the day salamander avoidance of snake cues occurs independent of snake diet, but late at night avoidance is apparently restricted to cues from snakes feeding on red-backed salamanders (Madison et al. 1999a,b). One limitation of these studies is that few diet treatments were tested, leaving the possibility that alternative diets might also elicit late night avoidance.