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Why can donkeys/mules jump from a standstill?
 Moderated by: DrDeb  
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Redmare
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 Posted: Mon Mar 20th, 2017 04:04 pm
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Since I last posted I have become owner of two miniature donkeys and have been having a ball teaching them. In our play as well as in researching online and talking to breeders and trainers who specialize in donkeys and mules, I came to find out that they are known for their ability to jump significant heights from a standstill, whereas horses cannot do this.

Which has me curious: is there a physiological difference between horses and donkeys/mules that makes this possible? Is it that horses cannot jump from standstill at all, or is it just much more difficult for them to do so? I have never seen a horse do this, but watched as my boys navigated obstacles with complete ease.

Aloha
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 Posted: Mon Mar 20th, 2017 09:12 pm
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I have a mini donkey too. They sure are fun and entertaining aren't they?

I also have horses and I can assure you that they can jump from a standstill! My younger warmblood mare can jump straight up, all 4 off the ground from a standstill or from a levade.

The Spanish Riding School in Vienna (as well as the other old schools) perform the airs above the ground. Have a look at the Lipizzaners and their ability to leap! I once attended a morning training session in Vienna and there was a very young stallion who was very airborne while ridden. It was fantastic to watch. The rider did not punish or touch his mouth. Just rode through it quietly, while his comrades teased him (probably about getting dumped in public!). This horse was displaying his abilities that would be cultivated later in the training. I wish now I would have asked for that horse's name to see if he became an airs horse.

My old 3 Day Eventer, a few spot white Appaloosa gelding, could jump a 5' high vertical jump from a walk on the line (too chicken to try it under saddle LOL). I didn't do this with him regularly. Just one day I kept raising the bar just to see. His talent was wasted on me! I figure he's as close to having a Lipizzaner as I'll ever get.

My guess as to why a donkey would be more talented at this would be because they are smaller. Less weight to lift. And maybe pound for pound they are stronger than a horse? My mini donkey really doesn't leap around much. He does enjoy a good run though and is very playful at times.

DrDeb
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 Posted: Tue Mar 21st, 2017 12:13 am
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Yes, the smaller the horse, pound for pound the stronger it will be. This is because horses are three-dimensional objects. Consider:

If you have a cube (width X length X height) whose dimensions are 2 ft. X 2 ft. X 2 ft. (or 2 cm X 2 cm X 2 cm, it does not matter), and you double the height, then if it is to remain a cube all three dimensions must be doubled.

A cube measuring 2 X 2 X 2 has an internal volume of 8 units. This means it also weighs 8 "units": and again it does not matter what the units are, vis., the cube could be filled with styrofoam, lead, or hamburger. If it's filled with styrofoam obviously it will weigh less than if filled with lead; but the point is that, no matter what it is filled with, it will weigh 8 "units".

Now let's say we double the height of the cube (and thus also its width and length), so that now it measures 4 X 4 X 4 = 64 volume "units". What will it weigh? If it were initially filled with styrofoam, and the initial weight at a height of 2 was 1 lb., it will now weigh 8 lbs. If it were initially filled with lead, and the initial weight at a height of 2 was 10 lbs., it will after doubling the height weigh 80 lbs. The point is that it will NOT weigh 4 lbs. if filled with styrofoam, nor 20 lbs. if filled with lead. In other words, doubling the height of a cube results not in a volumetric=weight increase X 2, but rather X 8.

When we apply this to horses, the same principle holds. Weight increase with doubling of height in a horse is not X 8, because a horse's width is not equal to its height and length. Neither is any other mammal's. This has been studied, however, and the real data show that with doubling of height, the increase in volume=weight is about X 5 1/2. In other words, the point is again, that the increase in weight with doubling of height is MUCH more than X2.

At the same time, increase in height or weight has no effect on the relative size or power of the propulsive muscles; and this is why large horses are much weaker than small ones -- their muscles have all the same power, but the amount of mass that the shorter horse has to push is proportionally far less.

As to horses having the ability to leap into the air, Aloha is quite right; there is no real difference in terms of athletic capability between mules and donkeys vs. horses. There's a TB X Connemara at the stable I board my Oliver right now, who I have observed just for jollies cutting caprioles, one after another, in his pen. When I mentioned this to his young and capable rider, she said, "yeah! and he does that when I ride him sometimes too!"

 However, mules and donkeys do have this "rep". They are flatter-bodied, typically, than horses and thus weigh even less for their height, and that undoubtedly helps them. Also, mules in particular are "made of rubber" -- they have very flexible ribcages and their ligaments and tendons tend to be stretchier than in horses, giving them the ability to, for example, kick the syringe out of the veterinarian's hand with a hind foot while the vet is standing in front of the mule's neck. Or kick the cowboy's hat off while he's riding. -- Dr. Deb


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