Impact assessment research: use and misuse of habituation, sensitisation and tolerance in describing wildlife responses to anthropogenic stimuli

Abstract

Studies on the effects of anthropogenic activity on wildlife aim to provide a sound scientific basis for management. However, misinterpretation of the theoretical basis for these studies can jeopardise this objective and lead to management outcomes that are detrimental to the wildlife they are intended to protect. Misapplication of the terms 'habituation', 'sensitisation' and 'tolerance' in impact studies, for example, can lead to fundamental misinterpretations of research findings. Habituation is often used incorrectly to refer to any form of moderation in wildlife response to human disturbance, rather than to describe a progressive reduction in response to stimuli that are perceived as neither aversive nor beneficial. This misinterpretation, when coupled with the widely held assumption that habituation has a positive or neutral outcome for animals, can lead to inappropriate decisions about the threats human interactions pose to wildlife. We review the conceptual framework for the use of habituation, sensitisation and tolerance, and provide a set of principles for their appropriate application in studies of behavioural responses to anthropogenic stimuli. We describe how cases of presumed habituation or sensitisation may actually represent differences in the tolerance levels of wildlife to anthropogenic activity. This distinction is vital because impact studies must address (1) the various mechanisms by which differing tolerance levels can occur; and (2) the range of explanations for habituationand sensitisation-type responses. We show that only one mechanism leads to true behavioural habituation (or sensitisation), while a range of mechanisms can lead to changes in tolerance.

Do human activity and infrastructure disturb domesticated reindeer? The need for the reindeer’s perspective

“…As pointed out by Bejder et al (2009), the effects of human disturbance on wildlife are complex and cannot be captured solely by measures of range use or observations of animal behaviour. This is also true for free-ranging reindeer.…”

“…However, a possible increase in tolerance towards humans (habituation) could not be excluded. Even though habituation of reindeer to human activities would make the coexistence between modern society and reindeer herding easier in many ways, habituation is not unambiguously ''good'' (Bejder et al 2009). If, for example, reindeer are habituated to roads, both reindeer and humans can suffer because of an increase in the number of animal-vehicle accidents.…”

“…Habitation processes are hard to follow and seldom reported (Bejder et al 2009). The change in tolerance level towards a disturbance is more often reported.…”

“…Even though there are seemingly unaffected animals residing near human interventions, there may also be animals that have withdrawn from the area because of the disturbance. The overall reaction of the herd is based on a continuum of individual tolerance within the population (Knight and Cole 1995;Bejder et al 2009). Thus, despite the fact that some local short-term studies have found that reindeer may develop increased tolerance to human disturbance over time, it is risky to draw conclusions on how, for example, a permanent industrial expansion may affect animal populations on a larger scale (Bejder et al 2009).…”

“…It should be noted, however, that differences in tolerance are not necessarily an effect of habituation, although they are often misinterpreted as such (Bejder et al 2009). Although differences in tolerance to human activity can be measured, it is seldom possible to record true habituation or sensitisation processes in human-animal interactions.…”