Tripping a climbing creature

[Gez]

This situation just crept up in a PbP.

There's a creature (some monstrous vermin) climbing up a tree. I try to trip it with a whip. My aim is to set the vermin off-balance so that it plumets to the ground.

Are there any rules about the modifiers a creature gains to its Str/Dex check to resist tripping when it's climbing on a vertical surface? I'd think it gets a penalty because its situation is less stable than if it were on the ground.

 

[ken-ichi]

The vermin would gain the standard +4 for having more than two legs, but if the creature has a climb speed I would not give it any penalties as it can climb just about as good as it walks on the ground.
Seeing that tripping a flying creature that uses wings to fly causes them to fall, tripping a climbing creature would also cause it to fall. The vermin could probably make the Climb check to catch itself from falling though, it is a fairly difficult DC.

 

[Gez]

The thing is, if you're walking rather than climbing, there's not a lot of chance a tripping attempt will send you away from the ground you walk.