SOS Encounter: Route 4, Route 5, Route 6 + 2 more
Walk: Route 4 (50%), Route 6 (50%), Paniola Ranch (40%) + 2 more
Looking for Herdier? It isn't found in the wild in this game — evolve Lillipup (Level 16).
Its base catch rate is 255 out of 255 (higher is easier); the catch rate calculator works out your odds with each ball. For the look, the best colour match is Luxury Ball or Nest Ball.
Evolution: Lillipup → Herdier (Level 16) → Stoutland (Level 32).
Lillipup in every game · Pokémon Sun, Moon, Ultra Sun & Ultra Moon interactive map (Alola)