Savviness of prey to introduced predators

Abstract

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.

Prey responses to foxes are not determined by nativeness

“…Our study sites were distinct from papers in the dataset, in that we focused exclusively on desert landscapes where predators were protected. We filtered the dataset of Wallach et al (2022) to include only predation risk experiments where a Vulpes species was the predator. Including our field data, this left us with a final dataset of 19 studies comprising 80 experiments.…”

“…We conducted a meta-analysis including our results from our field study, to test the generality of our findings. We used the data on fox studies included in the meta-analysis by Wallach et al (2022), which explores the determinants of predator recognition in prey globally. This database was comparable to our field study because it was focused on small mammals ( < 2 kg), included only experiments conducted under free-ranging conditions sympatric with foxes, and on small mammals that had been born locally.…”

“…Using the Hedge's g effect sizes of the small mammals' responses to fox scent from the Wallach et al (2022) database, we constructed a random-effects meta-analytic model testing whether small mammal responses to fox scent could be predicted by fox nativeness. Modelling was undertaken using the function rma.mv in the R package 'metafor' (ver.…”

Preventing extinction in an age of species migration and planetary change

“…For the most part, conservation has set aside these paradoxes (but see 14 ) due to claims that introduced organisms have fundamentally different—and unwanted—effects relative to native ones ( 15 , 16 ). While we acknowledge that in specific cases (especially on islands) introduced organisms have contributed to extinctions, meta-analyses have repeatedly shown that it is impossible to distinguish between native and introduced organisms on the basis of their effects ( 17–21 ); that some ‘invasive’ organisms targeted for eradication turn out to be native endemic species ( 22 ); that introduced organisms are not a leading cause of biodiversity loss ( 23 ); and that when we look we find that many introduced organisms sustain ecosystem services and facilitate other species ( 24–28 ). While there remains disagreement about these points among conservation scientists, we cannot ignore the fact that continued exclusion and eradication of introduced populations may exacerbate extinction of vulnerable groups of plants and animals at a time of monumental planetary change.…”

Density and ecological drivers of free‐ranging cat abundance and activity in Madeira Island, Macaronesia

“…Mammalian alien predators are a particularly damaging group, having been implicated in the extinction of at least 87 birds, 45 mammals, and 10 reptile species worldwide (Doherty et al, 2016). As a result of evolutionary isolation, islands have a disproportionate share of global terrestrial biodiversity (Russell & Kueffer, 2019), with species often exhibiting "ecological naïveté"-that is, loss of defensive traits and behaviors needed to deal with novel predators (Carthey & Banks, 2014;Wallach et al, 2022)-making them particularly vulnerable to predation (Azumi et al, 2021;Courchamp et al, 2003;McCreless et al, 2016;Nogales et al, 2006). Although predation is often the most visible impact, invasive mammalian predators can also impact native biodiversity by competition, disease transmission, and through a wide range of cascading ecological impacts (Bourgeois et al, 2004;Carrete et al, 2022;Nogales et al, 1996;Rando et al, 2020).…”