How smart does a monster/NPC have to be to switch to grappling?

[Jon_Dahl]

An opponent has a very high AC or some other form of defense, such as invisibility. In many of these cases, the monster should abandon their primary attack mode and try to grapple the opponent instead.

My rule is that all monsters switch to grapple if they can't score a hit with a natural 15 or higher, and grappling seems like a viable choice (e.g. the opponent is smaller than then monster). With invisibility and such, I have no rule of thumb.

(Some campaign modules, such as the Red Hand of Doom, address this issue.)

[theboss]

I mean it really depends which monster are we talking. If it has a feat regarding grapple I would say his base int (even a 2) should suffice because grappling is a survival measure the monster has in order to hunt or protect it self. On the other hand, anything (humanoid or monstrous) without a feat should try to think other measures on an int score of 6 at least, because it would be trying to use a different tactic.

[Jay R]

It doesn't take intelligence to grapple. Pythons do it.

D&D assumes a dangerous world. Any species should evolve to using its best tactic in a given situation, or it will eventually be eliminated by the species that do.

[Buufreak]

Snakes naturally constrict. What int do they have? That. That is a non zero number.

[NotASpiderSwarm]

Even - Int monsters, like Monstrous Centipedes and Ogre Zombies, can probably grapple. All grappling is is grabbing whatever is trying to smack you and then bouncing that thing off the nearest hard surface. That's not something that takes actual thought.

[Batcathat]

Snakes naturally constrict. What int do they have? That. That is a non zero number.

While that's true, naturally constricting your enemies isn't quite the same as switching to grapple when hitting them isn't effective. A creature whose primary attack is hitting things won't just switch to grappling just as a python wouldn't suddenly start headbutting an enemy they couldn't constrict.

[Jay R]

A creature with animal intelligence will stop doing what doesn’t work to switch to something that does.

For instance, a hog-nosed Snake will simulate a straight by flattening out its neck. If that doesn’t scare the enemy away, it will play dead.

Other creatures have more than one response, and will stop using one if it isn’t working.

If they don’t develop this instinct, then they will not survive.

Really — animal intelligence is enough to switch tactics.

[Monsterpoodle]

Animal intelligence should be enough.. Bears, lions, rats will try and grasp something with their limbs when trying to bite them.

[Quertus]

Really, this is probably more a matter of Wisdom than Intelligence. I'm reminded of a comic with a young boy struggling to push open a door labeled "pull"; above the door is the sign "school for the gifted".

[OgresAreCute]

Apes (int 2) in the MM are described as trying to grapple heavily armored targets.