aurochs vs plains bison

aurochs

noun
  • The European bison (Bison bonasus, or Europæus). 

  • An extinct European mammal, Bos primigenius, the ancestor of domestic cattle. 

plains bison

noun
  • Bison bison bison, one of the two subspecies of the American bison, the other being the wood bison. 

How often have the words aurochs and plains bison occurred in a corpus of books? (source: Google Ngram Viewer )