Otters are one of the largest and most social members of the weasel (or Mustelidae) family. The weasel family has been around for a long time, first appearing around 15 million years ago. This group includes almost 60 different species including mink, ferrets, badgers, martens, wolverines, and more. The Mustelidae family inhabits all continents except Antarctica and Australia. All are primarily carnivores and most are active year-round.