[Posted without context, but also, by popular request.]
Fable convention has it that we meet one member of each animal type, and his species name is treated as his given name:
Frog and Badger went down to the lake where they saw that Duck had polluted it with his motorboat.
Treat the species names of such characters as proper names, capitalized accordingly, without the indefinite article. References to groups of creatures would not be capitalized, and would use the definite article:
“I am happy to be a bald eagle,” Bald Eagle said.
That is all.