Minecraft xbox 360: Do your farm animals die on their own?

1st question- do they eat each other? And 2nd- Do you need to feed them? I made a pen and my animals were in it for a long time, then all at once the sheep and pig I had (with the ocelot) were gone. Then eventually so was the ocelot. Did he eat them? O.o

No, they might of despawned

They can't eat each other only wolves can do that and feeding animals is for breeding with other animals but yes like the other guy said they might have despawned