What is a female deer called?

We call them “does”

The word does can refer to either a female deer (a whitetail doe) or to the female of any other ungulate. When used as a noun, it typically refers to a category that includes other related animals. When used as an adjective, it can refer to both males and females. For example: “A family group is called a herd; most domestic sheep are in herds.” The word “yearling”, as well, could be defined as meaning both males and females born the previous year, since they have not yet been classified by sex according to physical characteristics or maturity levels.