Does zoo visitor presence and noise impact the behaviour and enclosure use of zoo-housed Siamese crocodiles? A case study.

Investigations of captive reptile behaviour and welfare indicators are essential if management styles are to be advanced. Humans are an integral part of the zoo environment and are a factor to consider when evaluating animal behaviour and welfare. Although crocodilians have been kept in zoos worldwide for decades, there is limited research on captive individuals. As crocodilians are naturally sensitive to sound, the noise that zoo visitors generate has been suggested to affect how individuals behave and use their environment. This project investigated the behaviour and enclosure use of a pair of Siamese crocodiles Crocodylus siamensis in order to quantify their response to zoo visitor presence and noise output. Camera traps were used to record the behaviour of the crocodilians across 24-hour time periods. The sampling technique applied was an instantaneous focal sampling method with twominute intervals for state behaviour and an Electivity Index was applied to measure enclosure use of biologically relevant zones within the enclosures. The results identified that several variables were significant predictors of crocodilian behaviour, including ambient temperature, individual, time of day, visitor numbers and ambient noise (dB). Additionally, correlation analysis found that visitor numbers and ambient noise had only a weak, significant positive correlation (r=0.298, P=0.017). Most zones within the enclosure were underutilised by the crocodiles apart from zone 3 (the water bank). This demonstrates that hauling out areas between land and water (haul-out zones) may be of great value to the study crocodiles and it is therefore expected that these areas would be over-used. There is considerable scope for future research on crocodiles in zoos focusing on the biological differences between crocodiles that may affect sensitivity to visitor presence.