“…Moreover, during opening hours, visitors also increased the sound levels (Quadros et al, 2014; de Queiroz, 2018), and this could be disruptive for animals. Indeed, several zoo studies suggested that animals were negatively affected by visitor noise, with increased vigilance (Birke, 2002; Dancer & Burn, 2019; Larsen, Sherwen, & Rault, 2014), stereotypy (Sellinger & Ha, 2005), hiding (Farrand, 2007), and cortisol level (Owen, Swaisgood, Czekala, Steinman, & Lindburg, 2004). As the presence of visitors is one of the major differences between the zoo and the wilderness or laboratory (Hosey & Druck, 1987), it is imperative that their noise pollution be taken into account when dealing with animal welfare.…”