In all these cases, using animals simplifies the methaphor. We realize after reading 'Animal Farm' that Orwell was not talking about a small English farm, but that Animal Farm was a methaphor for communist Russia. After reading 'Watership Down', 'Plague Dogs', and to a lesser extent 'Shardik', the reader sees that humans and nature can coexist. Afterall, for all the suffering Hazel-rah's rabbit went through, he was saved from a cat by a girl. 'Watership Down' also has the benefit of the double-metaphor with the types of government.
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