Koala

A koala was a mammal strongly associated with Australia. (PROSE: Blue Box) It had a highly specialised metabolism that revolved around eating eucalyptus leaf. (PROSE: Sky Pirates!) Koalas are shy and mild creatures, meaning that they won't inhabit cities. The Twelfth Doctor once mentioned that he went to a planet where Koalas were the dominant species. (PROSE: Big Bang Generation)