All you have to do is bring about 5 tranq arrows (more for high lvl), stand at the top of the cliff bordering the swamp, and shoot it (mine took 3 hits before it went down). Then go down and feed it taming food (meat is fine) and wait. But remember to BRING NARCOTICS or do better and bring bio toxin like me. Now just defend your creature from the top of the cliff ( if you can get back up) and then you have your very own frog.