Deer

Deer, whose males were known as stags, were large, horned, quadruped mammals which were often the subject of taxidermy. As Hex observed, Joe Hartley's taxidermy workroom contained stuffed deer, including one that was in the process of being mounted. (BFA: Night Thoughts)

In about 120 AD, the Tenth Doctor learned that Roman authorities kept stags as a part of a menagerie that included leopards, elephants and a wide range of other, chiefly African animals. Some of the beasts were kept for hunting and others were used to face off against prisoners in local arenas. The Doctor was incensed by the practise, because he knew it would lead to the extinction of several of the species. (NSA: The Stone Rose)