On crystal isles,these are an easy find in the river that surrounds the biggest yellow crystal at the Eastern floating islands.
Easily at least 8 there at a time. Be sure to look at all the small lakes in the area you can find 2 in each of them at anytime.
If Mr. Krabs can pick up stegos, WHY CANT THEY PICK UP TRIKES!!?!??!?!?!?!?!?!?!?!?!?!?!? Pick things up with this, and tranq them with rifle, u can do it while mounted, or, thing u want to tame in one claw, snake in the other. Boo yah! U are welcome.
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)
The Karkinos is a massive crab-like creature in Ark: Aberration that can grab and smash creatures and players. It can also throw them at great lengths. Using its strong legs, the Karkinos can leap to impressive heights.