Resident Evil 2 lickers are, as the game explicitly states, completely blind. They hunt only using the sound of your footsteps. Although they will detect your presence if they manage to get within just a few footsteps of either Claire or Leon.

What virus makes lickers?

Lickers are the result of a mutation caused by the progression of the T-Virus infection in a zombified human host's body. They were named by Raccoon City Police Department personnel for their peculiarly long tongues.

How do you deal with the Lickers in Resident Evil 2?

When it comes to killing Lickers in Resident Evil 2, they're just about the toughest type of common enemy that you can encounter. If you're playing on Assisted mode, then one shot with Leon's shotgun or Claire's grenade launcher will kill them outright.