Assessment of predation risk through conspecific cues by anuran larvae

Accurate assessment of predation risk is critical for prey survival during predator–prey interactions. Prey can assess predation risk by the presence of cues dropped by predators themselves, but they can also gather information about risk level through cues released by other prey, avoiding the hazard of being in close proximity to predators. In this study, we examine the ability of anuran larvae (Pelobates cultripes) to detect predation risk indirectly when they are in contact with conspecifics that have been recently exposed to chemical stimuli from natural predators (larvae of aquatic beetles). In a first experiment, we confirmed that larvae exposed to predator cues exhibited innate defensive behavior, indicating that they perceived the risk of predation and, thus, could potentially act as risk indicators for naïve conspecifics. In a second experiment, we observed that unexposed larvae paired with a startled conspecific adjusted their antipredator behavior, presumably by mirroring conspecifics’ behavior and/or using chemical cues from their partners as a risk information source. This cognitive ability of tadpoles to assess predation risk through conspecific cues might play an important role in their interaction with predators, facilitating the early detection of potential threats to elicit appropriate antipredator responses and increase the chances of survivalFinancial support was provided by the Spanish Ministry of Science and Innovation (MICINN), under Grant CGL2015-68670-

Distribución, abundancia y conservación de la culebrilla mora (Trogonophis wiegmanni) en las Islas Chafarinas

Peer reviewe

Diferencias en la percepción del riesgo de depredación entre el galápago leproso (Mauremys leprosa) y el introducido galápago americano (Trachemys scripta elegans)

30 páginas, 8 figuras y 7 tables..La introducción de seres vivos fuera de su área de distribución natural representa, tras la pérdida del hábitat, la segunda causa de amenaza a la biodiversidad global (DEVINE,1998; IUCN, 2000; MACK et al., 2000). La introducción de especies exóticas afecta tanto a la estructura como al funcionamiento de los ecosistemas, desviando flujos de energía o desplazando especies nativas de sus nichos ecológicos (HERBOLD y MOYLE, 1986; WILLIAMSON, 1996). Los efectos de estas introducciones son generalmente impredecibles, a no ser que la demografía, el uso de los recursos y las relaciones bióticas de las especies hayan sido cuidadosamente investigadas, pero fenómenos de depredación, contaminación genética, introducción de patógenos y competencia entre especies invasoras y nativas parecen una consecuencia lógica derivada de este tipo de alteraciones (ELTON, 1958; DODD y SEIGEL, 1991; BUTTERFIELD et al., 1997; ARANO et al., 1995; MANCHESTER y BULLOCK, 2000)Peer reviewe

Factores que afectan a la competencia entre el galápago leproso (Mauremys leprosa) y el introducido galápago de Florida (Trachemys scripta)

Tesis doctoral inédita. Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Biología. Fecha de lectura: 18-12-200

Factores que afectan a la competencia entre el galápago leproso (Mauremys leprosa) y el introducido galápago de Florida (Trachemys scripta)

Tesis doctoral inédita. Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Biología. Fecha de lectura: 18-12-2009. 202 páginasPeer reviewe

Learned recognition of introduced predators determines survival of tadpole prey

Alien predators are one of the major causes for rapid decline and extinction of native species, because they often create novel ecological contexts in which the antipredatory responses of native organisms are no longer fit. Although larval amphibians are often capable of innately responding to chemical cues from local predators through changes in morphology and behaviour, naïve tadpoles generally cannot recognize introduced predators with which they have not shared an evolutionary past. However, in a few documented cases, aquatic organisms have been observed to alter morphology or behaviour in response to alien predators. Such a response may have evolved as adaptive recognition, increasing their repertoire of innate responses to include the novel predator or may have evolved as the prey's ability to learn new threats by association with conspecific alarm cues. The red swamp crayfish, Procambarus clarkii, is a harmful invasive species in aquatic systems world-wide, causing great ecological impact on native amphibian populations during the last decades through intense predation of eggs and tadpoles. We demonstrate that naïve tadpoles of the western spadefoot toad, Pelobates cultripes, are not capable of innately recognizing water-borne predator cues from the red swamp crayfish. Nevertheless, we demonstrate that P. cultripes tadpoles can learn to recognize the cues of the invasive predatory crayfish as a threat when they are exposed to predator cues combined with conspecific alarm cues. Finally, we show that tadpoles conditioned by joint exposure to crayfish and alarm cues enjoy higher survival during predation trials with invasive crayfish. Learning to recognize a newly introduced predator through association with conspecific alarm cues may allow successful generalization of antipredatory responses by tadpoles. This cognitive ability of tadpoles may contribute to reduce their vulnerability to alien predators and soothe the impact of invasions in natural populationsPeer reviewe

Low levels of chemical anthropogenic pollution may threaten amphibians by impairing predator recognition

Recent studies suggest that direct mortality and physiological effects caused by pollutants are major contributing factors to global amphibian decline. However, even sublethal concentrations of pollutants could be harmful if they combined with other factors to cause high mortality in amphibians. Here we show that sublethal concentrations of pollutants can disrupt the ability of amphibian larvae to recognize predators, hence increasing their risk of predation. This effect is indeed much more important since very low amounts of pollutants are ubiquitous, and environmental efforts are mostly directed towards preventing lethal spills. We analyzed the effects of two common contaminants (humic acid and ammonium nitrate) on the ability of tadpoles of the western spadefoot toad (Pelobates cultripes) to recognize chemical cues from a common predator, nymphs of the dragonfly Anax imperator. We compared the swimming activity of tadpoles in the presence and absence of water-borne chemical cues from dragonflies at different concentrations of humic acid and ammonium nitrate. Tadpoles reduced swimming activity in response to predator cues in the absence of pollutants, whereas they remained unresponsive to these cues when either humic acid or ammonium nitrate was added to the water, even at low concentrations. Moreover, changes in tadpole activity associated with the pollutants themselves were non-significant, indicating no toxic effect. Alteration of the natural chemical environment of aquatic systems by pollutants may be an important contributing cause for declines in amphibian populations, even at sublethal concentrations.Peer Reviewe

Asymmetry in food handling behavior of a tree-dwelling rodent (Sciurus vulgaris).

Asymmetry in motor patterns is present in a wide variety of animals. Many lateralized behaviors seem to depend on brain asymmetry, as it is the case of different tasks associated to food handling by several bird and mammal species. Here, we analyzed asymmetry in handling behavior of pine cones by red squirrels (Sciurus vulgaris). Red squirrels devote most of their daily activity to feeding, thus this species constitutes an appropriate model for studying asymmetry in food processing. We aimed to explore 1) the potential lateralization in handling of pine cones by squirrels, 2) the dominant pattern for this behavior (left- vs. right-handed), and 3) whether this pattern varies among populations and depending on the pine tree species available. Results revealed that red squirrels handle pine cones in an asymmetrical way, and that direction of asymmetry varies among populations and seems to be determined more by local influences rather than by the pine tree species

Background colour matching in a wild population of Alytes obstetricans

The capacity for physiological colour change has long been described in anuran amphibians. Camouflage against predators seems to be the most relevant function of dynamic changes in skin colour of frogs, but key aspects such as the rate at which these changes occur, or the specific colour components involved are not completely clear.Whereas most research on the topic has been reported on tree frogs in laboratory conditions, studies in other anurans or in the field are much scarcer. Here we show a potentially plastic, adaptive response in coloration of common midwife toads, Alytes obstetricans, from a population of central Portugal, whose pigmentation varied with their natural backgrounds. Using quantitative image analysis, we compared hue, saturation and brightness of dorsal skin coloration of toads and the colour of the area of ground immediately around them. We found a positive correlation between coloration of toads and background colour for the three components of the colour. As well as other anuran species, A. obstetricans might adjust skin coloration to match the surrounding environment, thus benefitting from short-term reversible crypsis strategies against predators. A less supported hypothesis would be that toads accurately select matching backgrounds to improve concealment as an antipredatory strategy.Funding was provided by MICINN project CGL2011-25062 (PI R. Márquez); additional financial support was provided by the MICINN Grant CGL2015-68670-R (PI N. Polo-Cavia).Peer Reviewe

Effects of coexistence and predator experience on antipredatory responses of montane amphibian larvae towards native and introduced salmonids

Amphibian larvae are known to display defensive behavior in response to water borne chemical cues from aquatic predators that they recognize as a threat, either innately or via learning. Such potential for adaptive behavioral plasticity may increase population resilience in montane habitats, where many unique amphibian assemblages have suffered from salmonid introductions. Here we present data from three experiments assessing the effects of coexistence and long-term experience with native and introduced salmonid predators on behavioral responses of larvae from montane populations of the Iberian frog, Rana iberica. Further, we examine the potential costs imposed by natural and exotic predatory threats on larval growth and development. Larvae coexisting both syntopically and allotopically with salmonids reduced activity to avoid detectability. Interestingly, larval activity levels increased and larval responsiveness to predators decreased after long-term exposure to waterborne cues from predatory fish, likely due to habituation. Exposure to predator cues during development did not affect larval growth but altered the timing of metamorphosis by reducing larval period. Although growth is not directly compromised and individuals increase their short-term probabilities to survive with aquatic predators by reaching metamorphosis earlier, they might face the costs of predation-induced responses and developmental acceleration in later life stages.The study was funded by the Spanish Ministry of Science and Innovation (MICINN; Grant CGL 2010-16285) to L. Boyero and J. Bosch. Additional financial support was provided by the MICINN; Grant CGL 2015-68670-R to N. Polo-Cavia