Tamed wolves and cats despawn

On a 1.4.2/1.4.5 Minecraft default server. 7 tamed wolves in a cobble fence pen, 3 dogs outside of said pen, pen of 15 sheep nearby, village with 7 villagers nearby, in a desert biome, leaving the wolves completely alone for a few days.
This is a unresolved bug from 1.2.5. If a tamed wolf (or group of wolves) is left alone (on a minecraft server) for a few Minecraft days (sometimes more), the whole group of them eventually despawn all at once. Possibly because other mobs spawning in the area eventually forces them to despawn?