Zoo visitor effect on mammal behaviour: Does noise matter?

The zoo visitor effect is the change in animal behaviour and physiology in response to the presence of a viewing public. It is thought to result from, amongst other things, visitor generated sound (i.e., noise), but this hypothesis has never been explicitly tested. We tested this hypothesis through observations on the behaviour and enclosure use of 12 mammal species held in 12 separate enclosures at the Belo Horizonte Zoo when exposed to different sound pressure levels (i.e., noise) from the visiting public. Noise pollution levels were significantly higher with the public present and increased with increasing audience size. Species that are more popular suffered greater noise pollution from the zoo visitors. No overall effects on behaviour were found in relation to noise levels, however, analysis of behaviour at the individual level found some significant differences. Notably, half of the individuals increased their vigilance behaviour with increasing sound levels and approximately one-third of individuals increased their movements. These results show that zoo visitors have a negative welfare impact on individual zoo-housed mammals, especially groups of noisy visitors where levels were recorded outside of the recommended limits for human well-being (>70 dB(A)). Thus, zoos need to address this issue, probably, through a combination of visitor education campaigns and acoustic modification to enclosures