Deer

From UnknowableWiki

Deer are herbivorous mammals. Male deer are called stags, while female deer are does. Stags grow and shed new antlers each year (WP).

James Potter's Animagus form is a stag, as well as his Patronus (BLC). His son Harry also has a stag Patronus (PA21).

Lily Potter's Patronus is a doe (DH36). Severus Snape also has a doe Patronus, reflecting his unrequited love for Lily (DH33).