Determinants of uncertainty in wildlife responses to human disturbance

Abstract

Outdoor recreation is increasing in intensity and space. Areas previously inaccessible are now being visited by ever-growing numbers of people, which increases human-wildlife encounters across habitats. This has raised concern among researchers and conservationists as, even in non-aggressive encounters, animals often perceive humans as predators and mount physiological and behavioural responses that can have negative consequences. However, despite all the research in recent decades, not many general patterns have emerged, especially at the level of populations, and many studies have yielded seemingly contradictory or inconclusive results. We argue that this is partly due to incomplete knowledge of the number and complexity of factors that may modulate the responses of animals. Thus, we aim to provide a conceptual approach intended to highlight the reasons that make it difficult to detect general patterns. We present a comprehensive compilation of factors modulating animal responses to humans at increasing levels (from sensory detection and immediate behavioural and physiological reactions, to changes in fitness and population trends), which may help understanding the uncertainty in the patterns. We observed that there are many modulating factors, which can be categorized as reflecting characteristics of the recreational activity itself (e.g. intensity of human presence), of the animals concerned (e.g. age or antipredatory strategy), and of the spatio-temporal context (e.g. habitat or timing of the encounter). Some factors appear to have non-linear and complex effects, which, if not considered, may lead to erroneous conclusions. Finally, we conclude that the difficulty in finding general patterns will be amplified at higher levels (i.e. at the level of populations), since as we proceed from one level to the next, the number of potential modulating factors accumulates, adding noise and obscuring direct associations between recreation and wildlife. More comprehensive knowledge about which (and how) factors affect animal responses across levels will certainly improve future research design and interpretation, and thus, our understanding of human recreational impacts on wildlife.

Unmanned aircraft systems as a new source of disturbance for wildlife: A systematic review

“…Animal responses to on-foot human presence [21], terrestrial vehicles [22–27] and aerial platforms such as manned aircraft, helicopters and gliders [28–30] may vary from punctual behavioral or physiological reactions to reductions in fitness (e.g. mortality by collision with the vehicles or stress-related decrease in productivity) or changes in spatial use (e.g.…”

The impact of disturbance from photographers on the Blue-crowned Laughingthrush (Garrulax courtoisi)

“…Wildlife responses to human disturbance may be detected at several levels, such as changes in sensory detection, physiology, behaviour, fitness, space use, and population growth rate (Tablado and Jenni 2017). Both comparative and experimental approaches have been used to assess individual behavioral, distributional, demographic, and population responses to human disturbance (Gill 2007, Kerbiriou et al 2009).…”

“…Both comparative and experimental approaches have been used to assess individual behavioral, distributional, demographic, and population responses to human disturbance (Gill 2007, Kerbiriou et al 2009). If animals respond behaviorally or physiologically to human disturbance, their fitness (reproductive output and survival as proxies) and habitat use may be compromised, even by single events (Bowles 1995, Knight and Gutzwiller 1995, Wingfield et al 1997, Frid and Dill 2002, Buckley 2011in Tablado and Jenni 2017. The decline of many species has been directly or indirectly linked to human disturbance (Reijnen et al 1996, Brawn et al 2001, Beebee and Griffiths 2005, Reed and Merenlender 2011.…”

Marine Mammal Behavior: A Review of Conservation Implications

“…It has also been argued that there are many modulating factors that can influence how wildlife respond to disturbance including; age, anti-predator strategy, habitat type, and even timing of the disturbance. As a result of these many confounding factors, some of which appear to have non-linear and complex effects, the difficulty of finding general patters may be amplified at higher levels of organization toward populations and species (Tablado and Jenni, 2015).…”