Tranq Arrows/Darts DO NOT WORK!!! To knock this out you need to use a catapult and shoot in only on it's back. If you shoot it on it's legs it will kill it.

@Stormwebb19

Cannon balls discrease taming effeciency significantly! So for high tame level, always use boulders. Please let other people know! :)

Pretty easy to tame. Trap it in a circular form of stone Dino gates, place catapult low if catapult is high the crab will die. Then shoot it with a catapult. Cannons insta kill the crab, do not use cannons

If you are missing with your catapult and it's dying, drag dino corpses to it and let the karkinos eat the corpses. It will heal him up a lot then try again with the same torpor you left off with.

This tame is like the Rock elemental, but do not shoot it in the head. Shoot it right in the back of it's shell. Anywhere else will kill it fast.

To the guy who said "rare on floaty islands on crystal" that is a load of crap found 20 on 1 ISLAND!!!

I understand that all the previous tips submitted were useful, but just in case it was not clear, hit the TOP OF THE CRAB, it will have a special animation if you hit it in the correct spot, and will take only a small amount of boulders to tame, even a high level. (Irrelevant with Cannons)

Knock out with catapult. Make sure to hit body to do torpor. Hitting legs damages it and doesnt knock it out. Shove rotten meat in it.

Put a catapult on a paracer, bring a high health turtle (carbomemys), whistle attack with the turtle and when the crab hits it put it in passive so you can easily aim and hit him on the body. No weird engineering needed.