It is well documented that animals take risk of predation into account when making decisions about how to behave in particular situations, often trading-off risk against opportunities for mating or acquiring energy. Such an ability implies that animals have reliable information about the risk of predation at a given place and time. Chemosensory cues are an important source of such information. They reliably reveal the presence of predators (or their presence in the immediate past) and may also provide information on predator activity level and diet. In certain circumstances (e.g., in the dark, for animals in hiding) they may be the only cues available. Although a vast literature exists on the responses of prey to predator chemosensory cues (or odours), these studies are widely scattered, from marine biology to biological control, and not well known or appreciated by behavioural ecologists. In this paper, we provide an exhaustive review of this literature, primarily in tabular form. We highlight some of the more representative examples in the text, and discuss some ecological and evolutionary aspects of the use of chemosensory information for prey decision making. Curiously, only one example illustrates the ability of birds to detect predator odours and we have found no examples for terrestrial insects, suggesting a fruitful area for future study.Résumé : Il est bien connu qu'un animal qui doit prendre une décision d'ordre comportemental prend en considération le risque de prédation associé à cette décision. Souvent, l'animal passera outre ce risque pour se reproduire ou se nourrir. Une telle habilité implique que l'animal a une information spatio-temporelle valable sur le risque de prédation. Les indices chimiques constituent une source importante d'informations. Ils révèlent la présence de prédateurs (où leur passage récent) et donnent des renseignements sur le taux d'activité du prédateur et sur sa diète. Dans certaines circonstances (dans l'obscurité ou en présence de prédateurs chassant à l'affût), les indices chimiques peuvent être les seuls permettant aux proies de détecter leurs prédateurs. Il existe une littérature abondante sur la réponse des proies aux indices chimiques (ou odeurs) fournis par les prédateurs. Ces travaux sont néanmoins disparates (leurs sujets s'étendent de la biologie marine au contrôle biologique), peu connus et peu appréciés des écologistes spécialistes de l'étude des comportements. Dans cet article, nous faisons une revue exhaustive de cette littérature, notamment sous la forme de tableaux. Nous mettons en relief dans le texte les exemples les plus représentatifs. Nous discutons aussi des aspects écologiques et évolutifs reliés à l'utilisation des informations chimiques par les proies lors de prises de décisions. Curieusement, un seul exemple illustre l'habilité des oiseaux à la détection des odeurs des prédateurs. Nous n'avons pas trouvé d'exemple chez les insectes terrestres. Il y a donc là un terrain potentiellement fructueux pour de futurs travaux.

Abstract. Over the last two decades, numerous studies have shown that alien predators contributed to amphibian population declines. Both experimental studies and correlative field surveys implicated alien species of fish, bullfrogs and crayfish as major contributors to amphibian population decline, and in some instances local extinction. Additional studies have demonstrated that alien predators also caused long‐term changes in aquatic communities. Recent studies have examined the feasibility of removing alien predators, and provide some evidence that amphibian populations can recover. Applying information gained from past studies to the recovery of amphibian populations will be the challenge of future studies. International, national and local policies that regulate alien predators should be based largely on the body of scientific evidence already in the literature. Scientists need to be more involved with policy‐makers to most effectively change laws that regulate alien predators.

Communities of larval amphibians in fishless habitats often differ strikingly from those in habitats with fish. We surveyed larvae of 15 amphibian species to determine if presence or absence of specific defenses against fish was correlated with breeding habitat. Each species was tested for two key defenses: unpalatability and chemically mediated predator avoidance. In eight of nine cases, larvae of species that often encounter fish had at least one of these defenses. In contrast, larvae of seven species that breed in fishless pools consistently lacked defenses against fish. Lack of appropriate defenses appeared to be a primary reason why temporary pool species cannot successfully coexist with predatory fishes in permanent habitats. Palatability and responses to chemical cues from fish often differed among closely related taxa and were correlated strongly with frequency of encounter with fish. Thus, natural selection rather than phylogeny best explains interspecific variation in antipredator defenses. Our data show that members of at least two orders and four families of amphibians use chemical cues to reduce predation risk from predatory fish.

Humans have effectively transported thousands of species around the globe and, with accelerated trade; the rate of introductions has increased over time. Aquatic ecosystems seem at particular risk from invasive species because of threats to biodiversity and human needs for water resources. Here, we review some known aspects of aquatic invasive species (AIS) and explore several new questions. We describe impacts of AIS, factors limiting their dispersal, and the role that humans play in transporting AIS. We also review the characteristics of species that should be the greatest threat for future invasions, including those that pave the way for invasions by other species (''invasional meltdown''). Susceptible aquatic communities, such as reservoirs, may serve as stepping stones for invasions of new landscapes. Some microbes disperse long distance, infect new hosts and grow in the external aquatic medium, a process that has consequences for human health. We also discuss the interaction between species invasions and other human impacts (climate change, landscape conversion), as well as the possible connection of invasions with regime shifts in lakes. Since many invaders become permanent features of the environment, we discuss how humans live with invasive species, and conclude with questions for future research.

No abstract