In the Pokémon TV series, Ash catches Tauros in the Safari Zone.
During the Safari Zone episode, Ash uses Safari Balls while exploring the protected area. He repeatedly encounters Tauros and eventually catches a large herd of them. The anime therefore presents Ash as owning 30 Tauros, even though one of them is usually treated as his identifiable battle partner.
Tauros later appears in several important battles after Professor Oak sends one to Ash. Its strength and aggressive charging style make it useful in League and Orange League competition. The capture is unusual because Ash catches many copies of the same species in one adventure.
Kangaskhan, Dratini, and Rhyhorn are all associated with the Safari Zone in Pokémon games or anime stories, which can cause confusion. The specific Pokémon Ash catches there is Tauros.