The effect of waterfowl signals and Pseudocorynosoma enrietti infection on the behaviour of the amphipod Hyalella patagonica.

In the present study, we sought to determine whether i) a waterfowl signal induces avoidance behaviour of the amphipod Hyalella patagonica, ii) infection by the acanthocephalan Pseudocorynosoma enrietti affects the behaviour of the amphipod, and iii) the parasite interferes with the amphipod response to waterfowl. We evaluated amphipod behaviour experimentally by measuring activity levels, phototaxis, geotaxis, and clinging behaviour. The main findings of this study indicate that uninfected amphipods show avoidance behaviour by reducing their activity in the presence of a predator signal. Secondly, infected amphipods show altered behaviour, such as swimming in bright areas near the water surface, which makes them more visible to predators in nature. Lastly, the presence of predatory cues causes infected amphipods to drop to the bottom, which increases their visibility to predators. The present research allows us to perceive the intricate interplay among predators, parasites, and their intermediate hosts and advance our understanding of these complex ecological dynamics.

Intraspecific variation in body size of bumblebee workers influences anti-predator behaviour.

Flower-dwelling predators make flowers dangerous foraging sites for pollinators, potentially affecting their anti-predator behaviour. Moreover, predation vulnerability often varies among pollinators' body sizes with interspecific comparisons showing that smaller species are more vulnerable than larger ones. However, how intraspecific body size variation influences pollinator behaviour under predation risk is still unknown, especially under natural conditions. We hypothesized that bumblebee workers of different sizes will exhibit different foraging strategies under predation risk. We predict that (a) small workers should more often exhibit anti-predator behaviours than larger workers. We also hypothesized that the anti-predator behaviour should be influenced by predator size and reward availability; therefore, we expect (b) higher avoidance behaviour towards larger predator sizes and (c) more and longer visits to inflorescences with high nectar availability. Finally, we expect that (d) nectar availability should overcome the anti-predator behaviour in less vulnerable, large, workers. We recorded flower visitation, time spent and rejection behaviours of different sizes of Bombus terrestris (Apidae) workers (large, medium and small) to inflorescences of Alstroemeria aurea (Alstroemeriaceae) with different treatments of artificial spiders (small and large) and nectar availability (with, without). Anti-predator and foraging behaviour of bumblebees was affected by the size of the worker, the presence of artificial spiders and nectar availability. Large and medium size bumblebees strongly reduced flower visitation and time spent in the presence of artificial spiders, consistently avoiding flowers with spiders, regardless of spider size or nectar availability. Instead, small bumblebees seldom modified their behaviour when facing artificial spiders, only increasing their avoidance or decreasing their foraging time in nectarless flowers hosting large artificial spiders. This pattern of larger workers being more sensitive to predation risk than smaller ones at the intraspecific level in B. terrestris is contrary to the expected and acknowledged trend based on previous interspecific comparisons, but partially consistent with predictions of models of optimal foraging theory. Intraspecific behavioural variability was uncovered only when nectar was available, whereas artificial predator size rarely modified bumblebee anti-predator and foraging behaviour. Therefore, our findings suggest that the trade-off between maximizing resource intake and minimizing predation risk strongly varies across bumblebee worker body sizes.

Resumen Los depredadores que cazan sobre flores hacen que éstas sean sitios peligrosos de forrajeo para los polinizadores, pudiendo afectar su comportamiento. En general, la vulnerabilidad a la depredación varía con el tamaño del polinizador, siendo en comparaciones interespecíficas las especies más pequeñas las más vulnerables. Sin embargo, aún se desconoce cómo la variación intraespecífica del tamaño corporal influye en el comportamiento del polinizador bajo riesgo de depredación, especialmente en condiciones naturales.. Esperamos que abejorros de distinto tamaño exhiban diferentes estrategias de alimentación ante el riesgo de depredación. Predecimos que (i) obreras pequeñas manifiesten con mayor frecuencia comportamientos anti depredadores que obreras más grandes. Conjuntamente, esperamos (ii) una mayor evasión hacia tamaños de depredadores más grandes, y (iii) más visitas y mayor permanencia en inflorescencias con néctar. Finalmente, esperamos que (iv) la disponibilidad de néctar prevalezca a la manifestación del comportamiento anti depredador en obreras grandes, supuestamente menos vulnerables. Registramos a campo el número de visitas, tiempo de permanencia y el comportamiento de evasión de diferentes tamaños de obreras de Bombus terrestris (Apidae) (grandes, medianas y pequeñas) a inflorescencias de Alstroemeria aurea (Alstroemeriaceae) con arañas artificiales (pequeñas, grandes) y distinta disponibilidad de néctar (con, sin). El comportamiento de los abejorros se vio afectado por su tamaño corporal, la presencia de arañas artificiales y la disponibilidad de néctar. Abejorros grandes y medianos disminuyeron considerablemente las visitas y el tiempo de permanencia en inflorescencias, evadiendo consistentemente las flores que albergaron arañas artificiales, independientemente del tamaño del modelo o la cantidad de néctar. En cambio, abejorros pequeños rara vez modificaron su comportamiento, aumentando la evasión y disminuyendo el tiempo de permanencia solo en flores sin néctar y con arañas artificiales grandes. El patrón encontrado a nivel intraespecífico en B. terrestris resultó ser opuesto al observado en comparaciones interespecíficas, pero parcialmente consistente con modelos de teoría de forrajeo óptimo. Esta variabilidad intraespecífica se manifestó solo cuando había néctar disponible, mientras el tamaño del depredador apenas modificó el comportamiento. Nuestros hallazgos sugieren que el balance entre maximizar la ingesta de recursos y minimizar el riesgo de depredación varía fuertemente con el tamaño corporal de los abejorros.

Chemosensory cues of predators and competitors influence search for refuge in fruit by the coconut mite Aceria guerreronis.

Organisms are adapted to recognize environmental cues that can provide information about predation risk or competition. Non-vagrant eriophyoid mites mainly avoid predation by using habitats that are difficult for predators to access (galls or confined spaces in plants) such as the meristematic region of the coconut fruit, which is inhabited by the phytophagous mites Aceria guerreronis and Steneotarsonemus concavuscutum. The objective of this study was to investigate the response of A. guerreronis to cues from the predators Neoseiulus baraki and Amblyseius largoensis in coconut fruits, cues from conspecifics (A. guerreronis injured) and cues from the phytophage S. concavuscutum. The test was carried out through the release of about 300 A. guerreronis on coconut fruits previously treated with cues from predators, conspecific or heterospecific phytophagous. We also observed the walking behaviour of A. guerreronis exposed to the same chemical cues using a video tracking system. The infestation of fruits by A. guerreronis was greater in the presence of predator cues and reduced in the presence of S. concavuscutum cues, but cues from injured conspecifics did not interfere in the infestation process. In addition, the cues also altered the walking parameters of A. guerreronis: it walked more in response to cues from predators and the heterospecific phytophage. Aceria guerreronis spent more time in activity in the treatments with clues than in the control treatment. These results suggest that A. guerreronis recognizes cues from predators and competitors and modifies its behaviour to increase its fitness.

The anti-predator role of within-nest emergence synchrony in sea turtle hatchlings.

Group formation is a common behaviour among prey species. In egg-laying animals, despite the various factors that promote intra-clutch variation leading to asynchronous hatching and emergence from nests, synchronous hatching and emergence occurs in many taxa. This synchrony may be adaptive by reducing predation risk, but few data are available in any natural system, even for iconic examples of the anti-predator function of group formation. Here, we show for the first time that increased group size (number of hatchlings emerging together from a nest) reduces green turtle (Chelonia mydas) hatchling predation. This effect was only observed earlier in the night when predation pressure was greatest, indicated by the greatest predator abundance and a small proportion of predators preoccupied with consuming captured prey. Further analysis revealed that the effect of time of day was due to the number of hatchlings already killed in an evening; this, along with the apparent lack of other anti-predatory mechanisms for grouping, suggests that synchronous emergence from a nest appears to swamp predators, resulting in an attack abatement effect. Using a system with relatively pristine conditions for turtle hatchlings and their predators provides a more realistic environmental context within which intra-nest synchronous emergence has evolved.

Do apprehended saffron finches know how to survive predators? A careful look at reintroduction candidates.

Wildlife trafficking is a major factor contributing to the reduction of biological diversity. In Brazil, trafficked animals are apprehended by environmental agencies and released in the wild. The maintenance of wild animals in captivity may jeopardize their survival in the wild, for example, by reducing their ability to recognize a predator. Saffron finches (Sicalis flaveola) are among the most trafficked Brazilian birds. Twenty-eight apprehended saffron finches were submitted to Temperament and Predator-recognition tests, with presentation of predator and non-predator models: a live and a taxidermised hawk, a taxidermised armadillo and a Lego cube. The captive saffron finches have retained general anti-predator responses, such as increasing alertness, avoiding back-facing and keeping distance when presented with potential predators. The birds responded more strongly to the live hawk than to the cube. Although some responses to the other stimuli were not statistically different from each other, a decrease in intensity of response with the decrease in threat level was remarkable. We found no relationship between temperament traits and responses to predators: a possible consequence of husbandry practices in captivity. Our results indicate saffron finches may retain basic anti-predator responses in captivity, which favours release and reintroduction programmes: information relevant for conservation management.

Sex differences in lizard escape decisions vary with latitude, but not sexual dimorphism.

Sexual selection is a powerful evolutionary mechanism that has shaped the physiology, behaviour and morphology of the sexes to the extent that it can reduce viability while promoting traits that enhance reproductive success. Predation is one of the underlying mechanisms accounting for viability costs of sexual displays. Therefore, we should expect that individuals of the two sexes adjust their anti-predator behaviour in response to changes in predation risk. We conducted a meta-analysis of 28 studies (42 species) of sex differences in risk-taking behaviour in lizards and tested whether these differences could be explained by sexual dichromatism, by sexual size dimorphism or by latitude. Latitude was the best predictor of the interspecific heterogeneity in sex-specific behaviour. Males did not change their escape behaviour with latitude, whereas females had increasingly reduced wariness at higher latitudes. We hypothesize that this sex difference in risk-taking behaviour is linked to sex-specific environmental constraints that more strongly affect the reproductive effort of females than males. This novel latitudinal effect on sex-specific anti-predator behaviour has important implications for responses to climate change and for the relative roles of natural and sexual selection in different species.