Ocelots despawn after being named with a nametag.

I am creating a "Menagerie" with all of the real-life mobs represented in Minecraft. However, I ran into a bit of a hiccup where Ocelots will despawn, despite being named. I took the precaution of naming all of my animals with nametags. I teleported far away from my Menagerie, and when I came back everything was just the way I left it--except all five of my ocelots had despawned.