Savviness of prey to introduced predators.

The prey naivety hypothesis posits that prey are vulnerable to introduced predators because many generations in slow gradual coevolution are needed for appropriate avoidance responses to develop. It predicts that prey will be more responsive to native than introduced predators and less responsive to introduced predators that differ substantially from native predators and from those newly established. To test these predictions, we conducted a global meta-analysis of studies that measured the wariness responses of small mammals to the scent of sympatric mammalian mesopredators. We identified 26 studies that met our selection criteria. These studies comprised 134 experiments reporting on the responses of 36 small mammal species to the scent of six introduced mesopredators and 12 native mesopredators. For each introduced mesopredator, we measured their phylogenetic and functional distance to local native mesopredators and the number of years sympatric with their prey. We used predator and prey body mass as a measure of predation risk. Globally, small mammals were similarly wary of the scent of native and introduced mesopredators; phylogenetic and functional distance between introduced mesopredators and closest native mesopredators had no effect on wariness; and wariness was unrelated to the number of prey generations, or years, since first contact with introduced mesopredators. Small mammal wariness was associated with predator-prey body mass ratio, regardless of the nativity. The one thing animals do not seem to recognize is whether their predators are native.

La hipótesis de la ingenuidad de la presa plantea que ésta es vulnerable a los depredadores introducidos porque se requiere que muchas generaciones atraviesen una coevolución lenta y gradual para que se desarrollen las respuestas de evasión adecuadas. La hipótesis supone que la presa será más sensible a los depredadores introducidos que difieren notoriamente de los nativos y de aquellos recién establecidos. Realizamos un metaanálisis global de estudios que midieron las respuestas cautelosas de mamíferos pequeños ante el rastro de meso depredadores simpátricos para probar estas suposiciones. Identificamos 26 estudios que cumplieron con nuestro criterio de selección. Estos estudios estuvieron conformados por 134 experimentos que reportaban las respuestas de 36 especies de mamíferos pequeños ante el rastro de seis meso depredadores introducidos y 12 nativos. Medimos la distancia funcional y filogenética entre cada meso depredador introducido y los meso depredadores locales nativos y el número de años simpátricos con su presa. Usamos la masa corporal del depredador y la presa como medida del riesgo de depredación. A nivel mundial, los mamíferos pequeños compartieron la cautela ante el rastro de los meso depredadores nativos e introducidos; la distancia funcional y la filogenética entre los meso depredadores introducidos y el meso depredador nativo más cercano no tuvieron efecto sobre la cautela; y la cautela no estuvo relacionada con el número de generaciones de la presa, o años, desde el primer contacto con los meso depredadores introducidos. La cautela de los mamíferos pequeños estuvo asociada con las proporciones de masa corporal entre el depredador y la presa, sin importar el origen. Lo único que los animales parecen no reconocer es si el depredador es nativo o no.

A novel trophic cascade between cougars and feral donkeys shapes desert wetlands.

Introduced large herbivores have partly filled ecological gaps formed in the late Pleistocene, when many of the Earth's megafauna were driven extinct. However, extant predators are generally considered incapable of exerting top-down influences on introduced megafauna, leading to unusually strong disturbance and herbivory relative to native herbivores. We report on the first documented predation of juvenile feral donkeys Equus africanus asinus by cougars Puma concolor in the Mojave and Sonoran Deserts of North America. We then investigated how cougar predation corresponds with differences in feral donkey behaviour and associated effects on desert wetlands. Focusing on a feral donkey population in the Death Valley National Park, we used camera traps and vegetation surveys to compare donkey activity patterns and impacts between wetlands with and without cougar predation. Donkeys were primarily diurnal at wetlands with cougar predation, thereby avoiding cougars. However, donkeys were active throughout the day and night at sites without predation. Donkeys were ~87% less active (measured as hours of activity a day) at wetlands with predation (p < 0.0001). Sites with predation had reduced donkey disturbance and herbivory, including ~46% fewer access trails, 43% less trampled bare ground and 192% more canopy cover (PERMANOVA, R2  = 0.22, p = 0.0003). Our study is the first to reveal a trophic cascade involving cougars, feral equids and vegetation. Cougar predation appears to rewire an ancient food web, with diverse implications for modern ecosystems. Our results suggest that protecting apex predators could have important implications for the ecological effects of introduced megafauna.

Animal cognition and culture mediate predator-prey interactions.

Predator-prey ecology and the study of animal cognition and culture have emerged as independent disciplines. Research combining these disciplines suggests that both animal cognition and culture can shape the outcomes of predator-prey interactions and their influence on ecosystems. We review the growing body of work that weaves animal cognition or culture into predator-prey ecology, and argue that both cognition and culture are significant but poorly understood mechanisms mediating how predators structure ecosystems. We present a framework exploring how previous experiences with the predation process creates feedback loops that alter the predation sequence. Cognitive and cultural predator-prey ecology offers ecologists new lenses through which to understand species interactions, their ecological consequences, and novel methods to conserve wildlife in a changing world.