Animals do not turn into zombies — only humans do. At least, that seems to be the rule so far in AMC's sci-fi zombie thriller, "The Walking Dead" (which airs Sundays at 9 p.m. EST/8 p.m. CST).

Some species of viruses, fungi, protozoans, wasps, and tapeworms take over the brains and actions of the animals and insects ... which turn their hosts into zombies. This is usually controlled ...