Snakes and forbidden fruits: non-consumptive effects of snakes on the behaviors of frugivorous birds

Abstract

Usually, incited by fear, prey try to detect stimuli that announce the presence of predators, which, in turn, must develop strategies to remain imperceptible. Although this relationship traditionally involves the consumption of prey, predators can also affect their prey through predator-induced alterations in foraging, habitat use, or morphology. These alterations in prey traits, resulting from non-consumptive effects, were investigated through different stimuli induced by artificial snakes on the anti-predator behavior of birds when foraging upon Morus nigra trees. Experiments were developed for each type of snakes static position reflected different states of foraging behavior adopted by snakes (i.e., sit-and-wait, coiled, and active foraging) using three treatments: artificial snake, snake-shaped mimicry, and control (i.e., no stimulus). Regardless of the behavior adopted by snakes, the models caused drastic changes to the behaviors of birds. The other treatments did not trigger behavioral changes, except for the snake-shaped mimicry treatment, which simulated a coiled snake. This study demonstrates how birds perceive and respond to different predator-like stimuli, highlighting the cognitive and behavioral abilities of vertebrates. Predators control prey populations through a combination of consumptive and non-consumptive effects. We investigated the effects of non-consumptive effects induced by different stimuli emitted by tree snakes on the anti-predatory behaviors of neotropical frugivorous birds when foraging upon M. nigra. Our results revealed that they react to predation risk by identifying conspicuous visual signals of their predators and therefore alter their foraging behavior, resulting in a decreased fruit-collecting rate. In addition, we presented a new perspective on the cognitive and learning capacities of neotropical frugivorous birds, investigating some attributes they use to locate and identify their predators.