Are you experienced? Predator type and predator experience trade‐offs in relation to tadpole mortality rates

Abstract

Cryptic behavior and unpalatability are common defensive strategies that occur in different taxonomic groups, but the effectiveness of these defensive strategies is context dependent, varying with predator type and co-occurring species. We tested this assumption by measuring the mortality rates of Eupemphix nattereri (cryptic behavior) and Rhinella schneideri (unpalatable) tadpoles in association with the predatory fish Oreochromis niloticus (vertebrate) and the dragonfly larvae of Aeshna sp. (invertebrate). We designed a second experiment to evaluate whether fish predators are capable of learning to avoid unpalatable prey once they have encountered it. Our results showed that fish preyed selectively on palatable tadpoles, avoiding unpalatable tadpoles and that the odonate larvae were more efficient in preying on the more active unpalatable tadpoles and less efficient in capturing those tadpoles that presented cryptic behaviors. Additionally, our data suggest that the antipredator traits of tadpoles can interact with each other, with cryptic tadpoles showing lesser mortality when co-occurring with unpalatable tadpoles and odonate predators. Unpalatable tadpoles also increase the mortality of cryptic tadpoles in the presence of experienced fish predators. These prey traits interact in modifying the prey preference of the predator, which constitutes a preyinduced trait-mediated interaction (TMI). This type of TMI is dependent on the system complexity (number of predator and prey species interactions) and could define food web properties, such as the role of predators and the number of competitor species in the system.

Anuran larvae as prey and hosts of invertebrates in Neotropical aquatic habitats

“…This may be due to their nutrition (they are suspension feeders), but similar movements could also be observed in S. fuscovarius at night. Constant movements in prey can be advantageous for invertebrate predators that demonstrate a sit-andwait foraging strategy and have been identified in R. schneideri and Itapotihyla langsdorffii tadpoles (Nomura et al 2011;Luiz et al 2013). However, new empirical and experimental studies are needed to assess whether E. bicolor is actually the most preyed upon tadpole species because of their constant movements.…”

“…Individuals can present both categories as predator avoidance mechanisms. According to Nomura et al (2011), tadpoles also present antipredator mechanisms that reduce their predator's capture success. Antipredator tactics, such as cryptic behavior and unpalatability, which do not involve modifying activity, can also occur in tadpoles.…”

Avaliação de risco e plasticidade comportamental limitada em girinos de Rhinella ornata (Anura, Bufonidae)

“…Eupemphix nattereri (Steindachner, 1863)], enquanto outros apresentam coloração conspícua, o que é geralmente interpretado como uma condição de aposematismo [e.g. Rhinella schneideri (Werner, 1894), R. ornata (Spix, 1824), R. crucifer (Wied-Neuwied, 1821)], por destacar o girino no ambiente, criando uma advertência aos predadores sobre a presença de substâncias impalatáveis em sua pele (eTeroVick, 2000;WeLLS, 2007;nomura et al, 2011). No entanto, a eficiência dessas estratégias defensivas podem variar de acordo com o tipo de estratégia de forrageio (hero et al, 2001; nomura et al, 2011) e com o nível de sensibilidade às substâncias impalatáveis (heyer et al, 1975; hero et al, 2001) dos predadores.…”

“…As baratas-d'água injetam toxinas que paralisam a presa e liberam enzimas digestivas que causam necrose nos tecidos da vítima (SWarT & feLgenhauer, 2003). Algumas larvas de libélula (e.g., gênero Aeshna) também não são afetadas pela impalatabilidade, apesar de mastigarem suas presas (croSSLanD & aLforD, 1998;nomura et al, 2011), e são consideradas importantes predadoras de girinos (hero et al, 2001).…”

“…No entanto, essas defesas induzidas são muito plásticas e podem ser influenciadas pelo estágio de desenvolvimento ontogenético do girino, diferentes níveis de palatabilidade, coexistência com predadores específicos, complexidade estrutural dos ambientes, entre outros (reLyea, 2003;koPP et al, 2006;richTer-boix et al, 2007;Jara & PeroTTi, 2009). Por exemplo, a complexidade estrutural no interior dos corpos d'água pode aumentar o número de refúgios para os girinos e diminuir o risco de predação (Tarr & babbiTT, 2002;koPP et al, 2006;Saha et al, 2009), entretanto, diferentes substratos podem servir de poleiro e influenciar positivamente o sucesso de forrageio de predadores invertebrados, principalmente aqueles com estratégia do tipo senta-e-espera e guiados por pistas táteis e visuais, como as larvas de Odonata e belostomatídeos (Hemiptera) (PriTcharD, 1965;Werner et al, 1983;azeVeDo-ramoS et al, 1992;Warfe & barmuTa, 2004;TobLer et al, 2007;nomura et al, 2011).…”