aurochs vs zubr

aurochs

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

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

zubr

noun
  • The wisent, the European bison (Bison bonasus). 

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