reindeer vs reindeers

reindeer

verb
  • To herd or farm reindeer 

noun
  • Any species, subspecies, ecotype, or other scientific grouping of such animals. 

  • Any Arctic and subarctic-dwelling deer of the species Rangifer tarandus, with a number of subspecies. 

reindeers

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