I think that this is interesting: "Of 78 recorded escapes in that period, only 66 animals were recovered." When Melbourne zoo animals run wild | Herald Sun
This whole story sounds really weird. Aardvarks escaped from Melbourne Zoo last year!?! "217 animals disappeared between January 2010 and September last year." Seriously? What was left? "Details of injuries to staff and visitors reveal zoo workers commonly suffer bites from pythons, bats and seals." Now this does surprise me -- zoo workers get bitten by animals?! Shock horror! When Melbourne zoo animals run wild | Herald Sun