Fear and stressing in predator–prey ecology: considering the twin stressors of predators and people on mammals

Abstract

Predators induce stress in prey and can have beneficial effects in ecosystems, but can also have negative effects on biodiversity if they are overabundant or have been introduced. The growth of human populations is, at the same time, causing degradation of natural habitats and increasing interaction rates of humans with wildlife, such that conservation management routinely considers the effects of human disturbance as tantamount to or surpassing those of predators. The need to simultaneously manage both of these threats is particularly acute in urban areas that are, increasingly, being recognized as global hotspots of wildlife activity. Pressures from altered predator–prey interactions and human activity may each initiate fear responses in prey species above those that are triggered by natural stressors in ecosystems. If fear responses are experienced by prey at elevated levels, on top of responses to multiple environmental stressors, chronic stress impacts may occur. Despite common knowledge of the negative effects of stress, however, it is rare that stress management is considered in conservation, except in intensive ex situ situations such as in captive breeding facilities or zoos. We propose that mitigation of stress impacts on wildlife is crucial for preserving biodiversity, especially as the value of habitats within urban areas increases. As such, we highlight the need for future studies to consider fear and stress in predator–prey ecology to preserve both biodiversity and ecosystem functioning, especially in areas where human disturbance occurs. We suggest, in particular, that non-invasive in situ investigations of endocrinology and ethology be partnered in conservation planning with surveys of habitat resources to incorporate and reduce the effects of fear and stress on wildlife.

Mismatch Between Risk and Response May Amplify Lethal and Non-lethal Effects of Humans on Wild Animal Populations

“…Signal detection and error management theory show that, in general, animals tend to overrespond to potentially risky stimuli (Johnson et al, 2013;Orrock et al, 2015), given that the possibly lethal cost of Type II error (under-response) is greater than the energetic and opportunity costs of Type I error (over-response; Bouskila and Blumstein, 1992). However, given the many neutral anthropogenic cues that animals may associate with some degree of risk, this "erring on the side of caution" can be costly (Fardell et al, 2020). Mismatch can thus amplify the risk or non-lethal effects of anthropogenic stimuli, which can have a far greater cost than those from predation given the widespread nature of human disturbance (Venter et al, 2016) and the maladaptive nature of Type I errors (Carrete and Tella, 2013;Møller et al, 2014).…”

Are physiological and behavioural responses to stressors displayed concordantly by wild urban rodents?

“…Anthropogenic disturbances are increasing the incidence of novel interactions between people, wildlife, and the environment, creating an imperative for conservation biologists to better understand and manage wild animal stress responses (Clinchy et al 2016 ; Carthey and Blumstein 2018 ; Otto 2018 ; Fardell et al 2020 ). Responses to a stressor depend on the perceived threat and its interpretation (Boonstra 2013 ) and may be the product of adaptation or plasticity and habituation.…”

Occurrence of Conspecific in the Neighboring Space Influence on Flight Initiation Distance in Cape Hare <i>Lepus capensis</i> under Human Stimuli

“…For example, yellow-bellied marmots M. flaviventris that made suboptimal decisions as to relative time spent foraging versus hiding from humans had lower body mass and increased over-winter mortality [14]. Social and ecological factors may impact prey escape reactions to human and non-human predators [15] [16]. The effect of group size on FID is well documented in terrestrial organisms, but highly inconsistent between studies, ranging from strong positive [17], to negative effects [18].…”