All animals are either Beasts or Creatures. This is usually consistent for a given species, but not always; for example, most dogs are Beasts and most cats are Creatures, but occasionally one will encounter a cat who is clearly a Beast, or dog who's an absolute Creature.
some of the illustrations I contributed to my friends’ solo-journaling game, Apawthecaria. you can pre-order the Ist printing now for fullfillment in June!
Thesis: while strictly speaking a "beast" is any non-human animal, archetypally a "beast" is a large quadrupedal vertebrate, and the further an animal is from embodying that archetype, the funnier describing it as a "beast" becomes.