Should a creature's CR be higher when it's on its home turf?

[johnsemlak]

Creature's fighting on their home turf (sorry for the Americanism), whether it be their lair, a place they've been able to organize a defence, or whatever, are generally tougher to overcome than those not. Other special envirnment conditions also affect the situation.

If a monster has some special advantages based on the area conditions (say, a special envirnment that make undead more powerful, for example), should their DC be higher?

 

[Zappo]

I think the DMG specifies that an encounter's EL can be modified by circumstances. If the creature has set up its lair to gain advantages, it is more difficult to beat and the EL should be modified accordingly. This doesn't only happen when the creature is on its own territory; there are plenty of situations where one of the parties could use the terrain and circumstances to its advantage.