#1 How much can they carry?
My two standard donkeys are 48in & 49in at the shoulder and about 450-500lbs. The internet will tell you that you can pack 15%-30% of their body weight. If Joe Blow had a fat yard ornament of 500lb donkey and you put 100+lbs (20+%) on its back, you are not going to get far from the trailer.
It largely depends on how conditioned your animals are. With horses/mules you have more wiggle room just because of the size of the animal. A poorly conditioned horse can carry more gross weight just because of its sheer size. That margin becomes smaller as the size of your animal shrinks.
I do 3-4 pack burro races a year and at least that many training runs then 4-6 backcountry pack trips, and with maybe 4 conditioning hikes before that. This has gotten me to where my donks can carry 70lbs of total pannier weight per animal, easy. I have done heavy loads out, one way, of 110lbs. Regardless, I have rarely pulled off a sweaty saddle pad.
#2 Aren’t they stubborn?
You cannot scare or negatively pressure a donkey into something they do not want to do. A standard donkey is just big enough to overpower you, and they know that. Their self-preservation instinct is so strong that they often stop and want to find a reason why for what they are doing. I have heard this is because they evolved in rockier, more mountainous terrain in Africa with smaller predators, where a stand and fight approach was more successful than flight.
Overall, this has made me stop think about how I am reacting to the animal or situation. I ended up with two great tempered donkeys, especially Cisco. He is my rock and willing to do anything I ask, because he had an amazing owner before me.
Julia took me three hours to get her into a two horse straight load trailer for the first time. Then a hour, then half hour, then back to a hour, then ten minutes. Now she willingly hops in 9 out of 10 times. The tenth time she waits for a nice audience at a trailhead and balks for a few minutes to put on a show.
This “stubbornness” saved my ass numerous times as a new backcountry packer. I have put them in numerous situations where I should have had a rodeo, a dead donkey, or a injured myself. Their innate ability to freeze with a rolled pack, leg stuck in mud, or getting stranded over a big log is a blessing for new packer.
#3 How much water do they need?
I get this one mostly from the hunter crowd looking to get some type of pack animal.
Pack llamas are very popular right now and pack goats are not far behind. I came pretty close to getting llamas (owning a burro blog) . Llamas and goats have been toted as being able to walk on water, let alone never having to drink it. I don’t know a ton about them, but given that goats, llamas, and donkeys all have successfully thrived in desert environments, I would guess their water requirements are similar.
I offer my burros water twice a day, usually in a pannier bucket. Do they drink each time? Usually not, but good animal husbandry requires you to offer it. One of my first trips in the Gila Julia did not drink water for a day and a half. If there is ample dew on the grass they eat then it is not uncommon for the water in my bucket to hardly move over a couple days.