Fresh tracks trail the area...

Consider Kassoon's Combat Encounters

Party has a Scout: Perception Check; DC depending on creature Stealth;
No Scout: average Passive Perception against creature Stealth;
Party is ambushed on fail.

Survival to identify and track the creature(s).
Resolve: {75%? **The lair is near**, containing x3 as many creatures if it isn't solitary|25%?**There's no lair nearby**}.