The domestic thylacine is descended from thylacines that were brought back by humans in 1970's and some were later domesticated as pets in 1980's. There are now more than 1,550 breeds of domestic thylacines, ranging from poodle-size critters to great dane-sized animals. They were bred to be more tame, more bold, less timid, and less aggressive than their wild ancestors. They are the most popular extinct mammal pets, about as popular as domestic cats. They are also very common as free-roaming animals and guide animals.