I'm 100% sure he's only 50% donkey.
Donkeys and mules have such wise eyes, and I absolutely love his. I've had the mule in my avatar for about 2 1/2 years now, and she has taught me so much about dealing with a skittish longear. As Corinne said, you need to be very patient with them. Earning their trust takes time. When I first got Betsy, she regarded any physical contact with distrust. Now, she willingly gives mule hugs!
You can't strong-arm a mule, like you might a horse, or it will come back to bite you (sometimes literally!) They are very smart animals that are very fast learners, and have memories that put an elephant's to shame.
Mules have a longstanding reputation for hating dogs. I remember seeing an antique mechanical bank that was a mule, trying to stomp a dog that popped out from behind a tiny hay bale! As has been said before, I wouldn't count on a mule being protective, but I wouldn't trust a dog's safety around any mule I didn't know well, and particularly around some that I do.
You may or may not have gotten your herd protector, but you have certainly gotten a potential friend for life!
