[Game mechanics] When Juveniles grow up while by a fence, they end up upon it and can leave
1
votes
The 3d model of a juvenile (buffalo at least is where I watched this happen) is slightly smaller than its mature version. They often stand close by the fence touching it, and when their model changes to the larger version, they are placed upon the fence. So they are free to leave and get killed somewhere on their way to a water source or while daydreaming, which players may interpret as a disappeared juvenile.