These are stuffed animals who were displayed at the wallanganda exposition. Since this exposition was a complete failure, they removed all the stuffed animals and other artefacts, and build an indoor playground instead. The stuffed animals are now on display in an empy building in the park. I rather see some living animals here, but this is stil better than an empty building offcourse....
No, they don't stuff every animal that dies here. Some are, but most ( like 99%) are destroyed, after section to determine the cause of death. The emphasis is on section, because determining the cause of death could mean to spot a contageous disease ( or other harmfull things like stuff visiors feed to animals)in an early stage.