It is very easy to tame. Just get a couple of mejoberries, stay close to him and give him one whenever he's hungry, through passive taming. Just be careful not to let any predators approach, wait less than 10 minutes and you will have your pet Lysto. If it is female it is useful for eggs, otherwise it only acts as a companion (in addition to making poo useful as a fertilizer).
Ok so if you are on mobile, I figured out how to tame them with no violence. I put amarberries in my hotbar guessing that was like have them "out". Started following g this little guy around, and behold, his tame meter started rising!