Dexter, the Pokédex, is knowledgeable about almost all of the Pokémon in the world, but there are some that still have yet to be categorized. Nidoran, and the entire species of Nidoran, have very limited information available. The Pokédex has this to say about the female Nidoran: Although small, the Nidoran’s venomous barbs render this Pokémon dangerous. The female of this species has smaller horns than the male.
First appearance: Ash has not yet encountered a Nidoran
