Abstract
Nature-based tourism is gaining extensive popularity, increasing the intensity and frequency of human-wildlife contacts. As a consequence, behavioral and physiological alterations were observed in most exposed animals. However, while the majority of these studies investigated the effects of punctual exposure to tourists, the consequences of constant exposition to humans in the wild remains overlooked. This is an important gap considering the exponential interest for recreational outdoor activities. To infer long-term effects of intensive tourism, we capitalized on Odontostilbe pequira, a short-lived sedentary Tetra fish who spends its life close to humans, on which it feeds on dead skin. Hence, those fish are constantly exposed to tourists throughout their lifecycle. Here we provide an integrated picture of the whole phenomenon by investigating, for the first time, the expression of genes involved in stress response and neurogenesis, as well as behavioral and hormonal responses of animals consistently exposed to tourists. Gene expression of the mineralocorticoid (and cortisol) receptor (mr) and the neurogenic differentiation factor (NeuroD) were significantly higher in fish sampled in the touristic zone compared to those sampled in the control zone. Additionally, after a simulated stress in artificial and controlled conditions, those fish previously exposed to visitors produced more cortisol and presented increased behavioral signs of stress compared to their non-exposed conspecifics. Overall, nature-based tourism appeared to shift selection pressures, favoring a sensitive phenotype that does not thrive under natural conditions. The ecological implications of this change in coping style remain, nevertheless, an open question.
Highlights
Humans are currently occupying all continents, generating different sources of threats to other species, known as human-induced rapid environmental change (HIREC) (Sih, 2013)
Fish from tourism and control zones differed in brain gene expression, cortisol levels in a new environment and behavioral responses to a stimulus
The fish density was highest in the tourism zone (TZ) compared to the control zone (CZ) (33.5 fish/m2 vs. 2 fish/m2)
Summary
Humans are currently occupying all continents, generating different sources of threats to other species, known as human-induced rapid environmental change (HIREC) (Sih, 2013). Several deleterious effects accompanying nature-based tourism were reported worldwide, such as pest transmission (Köndgen et al, 2008), habitat destruction (Ballantyne et al, 2014) or exotic species introduction (Anderson et al, 2015). All benign human-wildlife interactions do not necessarily result in such dramatic negative events, they almost always lead to small or unnoticeable, changes in animal behavior and physiology (Geffroy et al, 2015, 2016). No general pattern has emerged to characterize the effects of nature-based tourism on physiology and behavior of wildlife species (Tablado and Jenni, 2015). While some animals display signs of habituation to human presence, characterized by reduced stress responses to human visitation, others sensitize instead (Tablado and Jenni, 2015; Geffroy et al, 2017)
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