Interesting question - is there a reason to break them up? I originally created this list until RIA bought it. The reason I split up the animals is because people view them differently. People who will not eat mammals often eat fish or poultry. Peter Singer, the utilitarian philosopher, and author of 'Animal Liberation' gives his tentative OK to eating shellfish, but not dairy, for instance. I was interested to read how or if people assess different types of animal food differently.