Can we save large carnivores without losing large carnivore science?

Abstract

a b s t r a c t a r t i c l e i n f oLarge carnivores are depicted to shape entire ecosystems through top-down processes. Studies describing these processes are often used to support interventionist wildlife management practices, including carnivore reintroduction or lethal control programs. Unfortunately, there is an increasing tendency to ignore, disregard or devalue fundamental principles of the scientific method when communicating the reliability of current evidence for the ecological roles that large carnivores may play, eroding public confidence in large carnivore science and scientists. Here, we discuss six interrelated issues that currently undermine the reliability of the available literature on the ecological roles of large carnivores: (1) the overall paucity of available data, (2) reliability of carnivore population sampling techniques, (3) general disregard for alternative hypotheses to top-down forcing, (4) lack of applied science studies, (5) frequent use of logical fallacies, and (6) generalisation of results from relatively pristine systems to those substantially altered by humans. We first describe how widespread these issues are, and given this, show, for example, that evidence for the roles of wolves (Canis lupus) and dingoes (Canis lupus dingo) in initiating trophic cascades is not as strong as is often claimed. Managers and policy makers should exercise caution when relying on this literature to inform wildlife management decisions. We emphasise the value of manipulative experiments and discuss the role of scientific knowledge in the decision-making process. We hope that the issues we raise here prompt deeper consideration of actual evidence, leading towards an improvement in both the rigour and communication of large carnivore science.

Environmental effects are stronger than human effects on mammalian predator-prey relationships in arid Australian ecosystems

“…Rather, it appears that hopping-mice fear predation by dingoes just as much as they fear predation by foxes or cats, which have each been shown to pose similar risks to hopping-mice (Coutts-Smith et al, 2007;Allen and Fleming, 2012). Differences between our results and those of previous studies are likely related to differences in experimental designs, with all previous studies based on small spatiotemporal scales and/or correlative study designs, in contrast to our large spatiotemporal scale and comprehensive experimental approaches (Allen et al, 2013b;Allen et al, 2017).…”

“…However, there remains a dearth of studies demonstrating these expected functional relationships for many threatened fauna persisting in desert ecosystems, and identifying the strongest factors influencing prey populations has proved difficult (Holmes, 1995;Marshall et al, 2014;Peterson et al, 2014). All components of food webs interact to some extent (Allen et al, 2017), but few interactions are strong enough to shape them. Although general ecological patterns may already be apparent, the outcomes of global environmental change are highly unpredictable, and 'the greatest single challenge will be to determine how context alters the direction and magnitude of effects on biotic interactions' (Tylianakis et al, 2008).…”

Study design concepts for inferring functional roles of mammalian top predators

“…It follows, then, that the local extinction of large carnivores and other top predators can be detrimental to biodiversity, and their subsequent reintroduction may produce positive biodiversity outcomes (Hayward and Somers, 2009;Ripple et al, 2014). However, despite (or perhaps because of) the simplicity of this concept and the wide array of literature on this issue, the function of top predators and their ability to generate these outcomes has attracted much debate and controversy Allen et al, 2017).…”

“…When the studies used to assess trophic relationships are flawed in design or have weak inferential ability, the interpretations about predators' roles within the system and the effects human management actions might have on them is perilous at best, and rightly contested. Achieving consensus is important, because the fates of many large predators are depending on the resolution of these debates, made possible only through improved scientific rigor (Allen et al, 2017).…”

“…Sufficient reliable evidence suitable for use in evidence-based management of top predators is presently lacking for almost all top predators (Ripple et al, 2014;Allen et al, 2017). Moreover, studies on the roles and functions of top predators continue to struggle to implement study designs having the potential to generate the necessary reliable evidence (Allen et al, 2013b;MacNulty et al, 2016).…”