Changes in animal management affect the behaviour of zoo animals. A decision to extend Taronga Park zoo (Sydney, Australia) opening hours at night for a month in spring caused staff to predict the likely effects on the animals. Predictions varied between species but included increased stereotypy, aggression and handling difficulties. Two data collection methods were used with nine focal species or groups selected using the staff predictions: dingoes; large macropods; mixed African ungulates; elephant; snow leopard; clouded leopard; Kodiak bear; chimpanzee; and orang-utan. For method 1, activity data were collected for 5hr/night either directly or from video footage using an instantaneous scan sampling method, with ad-lib recording of predicted behaviours, before and during the period of evening opening. Method 2 was a survey completed at exhibits recording animal visibility, activity and vocalisations, and visitor numbers before and during evening opening. T-tests were used to test differences in single attributes and G-tests to compare focal activity budgets between the pre- and extended opening periods. Data presented are means±standard deviation. Evening mean focal activity budgets did not differ significantly pre- and during opening, and mean frequency of predicted responses differed only for snow leopard, where % pacing increased (pre: 4±5, during:15±12% time; p<0.05). Predicted responses observed initially for focal animals moderated as animals appeared to become used to the changed conditions. Survey results confirmed the focal species observations and provided data on other affected species. When data from all exhibits were combined, the animal visibility index increased (pre: 36±31, during: 53±32% time; p<0.01) and time spent active increased (pre: 24±18, during: 35±28%; p<0.02) in lit exhibits during extended opening. The study addressed staff concerns and we concluded that there were few signs of continued stress, with animals rapidly adapting to the presence of visitors and changed management conditions of extended opening.