From what I remember when I stayed there, the animals are out at night but then each species goes inside at a certain time during the late morning when most guests are at the parks. The animals get their daily wellness checks and fed to encourage them to come inside and often they will wait outside their enclosure entrance (in the back, away from guest rooms) in anticipation of being let inside...similar to how the giraffes on the safari wait by their gate at times (or at least it was explained to me this way).
I stayed up late at night watching the animals outside from my balcony and not only were they active, they were quite entertaining!