ORIGINAL PAPER Looking through the predator’s eyes: another perspective in naı ¨vete ´ theory Larissa Strictar Pereira . Mirtha Amanda Angulo-Valencia . Thiago Vinicius Occhi . Andre ´ Andrian Padial . Jean Ricardo Simo ˜es Vitule . Angelo Antonio Agostinho Received: 10 October 2018 / Accepted: 20 April 2019 Ó Springer Nature Switzerland AG 2019 Abstract The topic of biological invasion has adopted the concepts of neophobia and dietary con- servatism to explain why some species are reluctant to include nonnative species in their diets, with prey naı ¨vete ´ predicting that prey would not be able to recognize novel predators in the environment. This is particularly true for fish, for which studies are rare, mainly in natural environments. Here, the existence of feeding selectivity in terms of prey origin was investigated in nature by quantifying the contribution of nonnative prey to the diets of native and nonnative predators. Three distinct rivers in the upper Parana ´ River basin (Brazil) and 13 piscivores were used to test the hypothesis. Out of the 650 possible trait combi- nations, only prey body shape (sagittiform) and predator relative body height were found to be correlated. Even though native and nonnative prey presented similar functional traits, very strong selec- tivity by prey origin was observed, with native predators positively selecting native prey. Native predators possibly do not recognize nonnative prey or lack the necessary ability to prey upon nonnative prey. Such findings show that, for several predators, prey origin does matter. There are many implications Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10530-019-01996-w) contains supplementary material, which is available to autho- rized users. L. S. Pereira Á T. V. Occhi Á J. R. S. Vitule Laborato ´rio de Ecologia e Conservac ¸a ˜o, Departamento de Engenharia Ambiental, Setor de Tecnologia, Universidade Federal do Parana ´, Jardim das Ame ´ricas, Curitiba, Parana ´ 81531-970, Brazil M. A. Angulo-Valencia Á A. A. Padial Á A. A. Agostinho Nu ´cleo de Pesquisas em Limnologia, Ictiologia e Aquicultura, Programa de Po ´s-Graduac ¸a ˜o em Ecologia de Ambientes Aqua ´ticos Continentais, Universidade Estadual de Maringa ´, Av. Colombo 5790, Maringa ´, Parana ´ 87020-900, Brazil A. A. Padial Departamento de Bota ˆnica, Universidade Federal do Parana ´, Jardim das Ame ´ricas, Curitiba, Parana ´ 81531-980, Brazil L. S. Pereira (&) Department of Wildlife and Fisheries Sciences, Texas A&M University, 534 John Kimbrough Blvd TAMU 2258, College Station, TX 77843, USA e-mail: lari.strictar@gmail.com 123 Biol Invasions https://doi.org/10.1007/s10530-019-01996-w