Tulcan can't be found in the wild. The only way to obtain one is by evolving a Tuwai.

How do you evolve tuwai?

Once you defeat the guardians, you can use the shrine to evolve Tuwai into Tukai. Leveling your new Temtem to a high enough strength is the toughest part of acquiring these two rare Temtem. You can power-level your team at the crystal shine where Tuwai is evolved into Tuvine.

How do you evolve Toucan Temtem?

To evolve Tuwai into Tuvine, you need to bring Tuwai to the Crystal Shrine on Tucma. The Crystal Shrine is inaccessible until you complete the 'Cultist Hunt' side-quest, also found on Tucma. On Tucma, travel to the far western island with the grapple-shot and talk to Valentina. She'll give you the 'Cultist Hunt' quest.