harbor seal vs sea leopard

harbor seal

noun

  • A species of true seals, Phoca vitulina. 

sea leopard

noun

  • The harbor seal, Phoca vitulina. 

  • Hydrurga leptonyx, of the Antarctic Ocean 

  • Leptonychotes weddellii, of the Antarctic. 

How often have the words harbor seal and sea leopard occurred in a corpus of books? (source: Google Ngram Viewer )