Strong food odours mask predation risk and affect evocation of defence behaviours in the tadpoles of Sphaerotheca breviceps

Abstract

Tadpoles of Sphaerotheca breviceps detect food and predators using waterborne chemical cues (odours), which evoke appropriate behaviour. The present study aimed to determine whether they are capable of resolving the conflict between foraging choice and predator avoidance on encountering both food and predatory chemical cues together. Experiments were designed using an association choice apparatus in which prey tadpoles were given a choice to move themselves close to or away from a given stimulus (food or a predator). Food odours were either strong or weak. Tadpoles of Hoplobatrachus tigerinus (n = 4) were placed in an open-ended mesh cage wrapped in a cheese cloth that provided predator cues. The time spent by the test tadpoles in the predator’s zone or away from it and the time spent feeding were recorded for 10 min (n = 25 trials). When food odours were weak, the prey tadpoles avoided predators and spent significantly more time in the predator-free zone. In contrast, when food odours were strong, they foraged equally in the two zones of the test apparatus regardless of the presence or absence of predators. These findings confirm the inherent ability of S. breviceps tadpoles to distinguish between food and predators, and indicate that strong food odours mask predation risk. We suggest that foraging theory and the predation risk allocation hypothesis should include factors that mislead prey during predation risk assessment and the evocation of defence behaviours.