Answer: Why Dog Eats Its Own PuppyI'm not sure, but it could be because they sense something is wrong with it so they eat it so it doesn't have to suffer.
Blabale: That's sad. They would have to be on like some kind of drug or just gone crazy. Did that happen to you? Well, if it did I feel sorry for you. If you know the dog's background info, it might help to answer why. The answer above just like saying that the dog killed the puppy for being ugly, which does not make sense. If it was in pain and suffering, the dog would try to help it, not eat it.
Dogs do naturally eat there puppies if they can sense somethings wrong with it. they aren't us and don't have motherly instincts. Her instincts are to protect the ones that will do well in life. They weed out the weak ones.