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


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.

Significance statement

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.

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The authors thank the Graduate Ecology Program of the State University of Campinas (UNICAMP). CPBB received a post-doctorate scholarship from the National Post-doctoral Program/Brazilian Federal Agency for the Support and Evaluation of Graduate Education (Programa Nacional de Pós-Doutorado/Coordination for the Improvement of Higher Education Personnel—PNPD/CAPES). GQR received a research scholarship from the Brazilian National Council for Scientific and Technological Development (Conselho Nacional de Desenvolvimento Científico e Tecnológico—CNPq). Thanks to the Betânia Inn for granting access to its property, where we developed part of the field experiments. We thank Paulo Sérgio Bernarde and Guilherme Amaral for giving in the pictures included in Fig. 1. The authors thank Nicky Clayton and two anonymous reviewers for their valuable comments on the manuscript.

Author information

Correspondence to Crasso Paulo B. Breviglieri.

Ethics declarations

Ethical approval

We confirm that there are no competing interests for any of the authors. All research presented in the manuscript was conducted in accordance with all applicable laws and rules set forth by their governments and institutions. The access of researchers areas of study and the development of methodological procedures were authorized by the team responsible for Núcleo Picinguaba subordinate to the PESM, and the owner of the Inn Bethany. During our experiment, none of the vertebrate species involved was captured or even manipulated, because it is non-invasive methods. Therefore, specific licenses for capture, transport, or collection agencies are not required. It is also worth mentioning that the species of birds filmed throughout this study are not categorized in any degree of threat or are protected by law, according to state environmental agencies (SMA), national (MMA/IBAMA) or international (IUCN).

Additional information

Communicated by N. Clayton

Electronic supplementary material

Below is the link to the electronic supplementary material.

Tangara seledon behavior (i.e., mobbing) in response to the snake model. (MPEG 29516 kb)

Tangara seledon behavior (i.e., mobbing) in response to the snake-shaped mimicry treatment using vines simulating “coiled” behavior. (MPEG 45488 kb)


Bird species that foraged upon Morus nigra during the experiment. (DOCX 555 kb)


Mobbing behavior in the presence of the snake models. (DOCX 344 kb)


Tangara seledon behavior (i.e., mobbing) in response to the snake model. (MPEG 29516 kb)


Tangara seledon behavior (i.e., mobbing) in response to the snake-shaped mimicry treatment using vines simulating “coiled” behavior. (MPEG 45488 kb)

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Breviglieri, C.P.B., Romero, G.Q. Snakes and forbidden fruits: non-consumptive effects of snakes on the behaviors of frugivorous birds. Behav Ecol Sociobiol 70, 777–783 (2016) doi:10.1007/s00265-016-2101-7

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  • Bird anti-predatory behavior
  • Cognitive and behavioral abilities
  • Predator cues
  • Foraging behavior
  • Vertebrates