I have some friends who have a mammoth jack. I know he (Beauford) is very loving and friendly, they haven't had any problems training him except he is a bit lazy and slow but that may just be a individual thing.
They bought him to breed for mules. They aren't sure if he bred any of their mares since its been pasture done. It will be interesting this spring if any foals arrive. I'll be sure to get some photos up if there are any.
I know a mammoth jack like a donkey can breed to a horse and get a mule. A mule can't breed to a horse and get another horse or mule. At least normally, I have known it to take place but its rare.
From what I understand, in the rare case where a mule does reproduce, the offspring isn't a mule, it's wither 100% horse or 100% donkey, depending on what it was bred to. I think that's really cool.
I want a dressage mule!
I rode one once, and it was different compared to a horse. You definitely do have to convince them to do something other than just telling them. They are a lot of fun though. =)
Yes, I have been around some mammoth jacks but it has been a very long time. They are very loyal and can be very hard to handle because mules and donkeys are very smart (even if they don't seem that way sometimes). Mammoth jacks are donkeys and are therefore able to reproduce. Mules, however, are 99% of the time born sterile and are unable to reproduce even if they keep their parts. I have a miniature burro that is 25 and a belgian mule who is about 23 I guess. He is the sweetest thing and will work entirely off voice commands while driving. The mini is kind of a turd though. LOL. As for jumping, mules can usually jump higher than horses of the same size. I have seen Tiny (the belgian mule) clear a 5 foot chainlink fence as if it was only 1 foot tall. He was freejumping himself to get to the greener grass.