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Reproductive success in ducks is strongly influenced by prédation on the breeding grounds. Ducklings are targeted by a range of terrestrial, aerial and aquatic predators, giving a strong selective advantage to individuals and broods that have effective ways to avoid prédation. In experiments on naive mallard (Anas platyrhynchos) ducklings without an accompanying adult female we investigated the innate ability to identify and avoid threats at varying intensity from aerial, aquatic and terrestrial predators. Ducklings displayed increased vigilance in response to pre-recorded calls of predatory birds, representing a low level of threat. They did not react to visual and olfactory stimuli generated by motionless northern pike {Esox lucius). Neither did they show a strong response to caged American mink {Neovison vison) (visual and olfactory stimuli), although they avoided the area with the mink, indicating a certain level of recognition. High intensity threats were simulated by staging attacks from aerial (goshawk, Accipiter gentilis) and aquatic predators (northern pike). The aerial attack made ducklings dive and scatter under water, whereas the response to attack by pike was to run on the water and scatter in different directions. The lack of response to a 'passive' pike and the rather weak avoidance of mink indicate that olfactory cues are not as important in identifying a potential predatory threat by ducklings as are auditory cues. Visual cues appear to be of little importance unless they are combined with movement, and a clear response is only triggered when the intensity of predator threat is high. Mallard ducklings, thus, show an innate capacity to adjust anti-predator behaviour to different predator types and to threat intensity. Our study highlights the general trade-off between foraging needs and predator avoidance, but also second-order trade-offs in which innate avoidance behaviour towards one type of predator may increase prédation risk from another. [ABSTRACT FROM AUTHOR]

To examine (1) the effect of experience and rearing environment on learning and behaviour over time, and (2) when (or if) newly-emerged young begin to incorporate experience into their choices, we compared the activity levels and hunting-site preferences of newly-emerged laboratory and field-reared crab spiders (Misumena vatia (Clerck, 1757)). We split spiderlings from eight broods into cohorts (1) released on goldenrod (Solidago canadensis) in the field and (2) retained individually in the laboratory, but provisioned with Drosophila melanogaster. We then tested both field-retrieved and laboratory-reared individuals at days 3, 7, 14 and 21 for their (1) rate of activity in cages over 15 min and (2) choice of either goldenrod or wild carrot (Daucus carota), two frequent hunting sites in the field. The rearing environment clearly influenced the spiderlings' activity levels: field-reared spiderlings became more active than laboratory-reared spiders over time; however, their choice of flowers did not change, even though their experience differed. Thus, innate mechanisms dominated the spiders' early hunting-site choices, and experience only informed their decisions at later stages in ontogeny. The spiders may, therefore, have multiple mechanisms for learning that begin to operate at different times, since spiderlings improve their locomotor performance through experience, while failing to use early experience in choosing hunting sites at this early point in ontogeny. [ABSTRACT FROM AUTHOR]