The Aerodynamic Advantage of American Pharoah’s Short Tail

The Life

American Pharoah in training at Churchill Downs this spring. (Photo by Eclipse Sportswire)

American Pharoah has a funny tail. It isn’t a normal horse tail. It’s shorter. Much shorter.

The reason why has nothing to do with genetics. He once had a long, flowing, normal tail, just like all the other horses he grew up around on McKathan Brothers Farm in Florida. But then one day, it was gone. Some suspect that another young horse on the farm, Mr. Z, was the culprit. They say he bit the tail off. If that’s true, American Pharoah got the last laugh. Mr. Z got a mouthful of American Pharoah’s dust in the Kentucky Derby and Preakness.

American Pharoah’s trainer, Bob Baffert, felt bad for the horse. He wanted to fix it with some hair extensions. The horse’s owner, Ahmed Zayat, put the kibosh on that. “I said, ‘No, it’s kind of unique. How could you not spot him in the morning? Keep it, it’s fun,’ ” Zayat told the New York Times.

A lot of attention has been paid to the funny-looking tail since American Pharoah has been thrust into the spotlight on his way to two-thirds of the Triple Crown. Most people focus on how it makes the horse look, but what about how the tail affects the way the horse runs?

Peter Caruso says it has an impact. A physicist who works with aerospace engineers, Caruso says that, all else being equal, a shorter tail can give a racehorse an edge in speed.

“The faster a horse runs, the aerodynamic drag increases. And the back of a horse, that’s where all the downforce happens,” Caruso explained. “The slipstream that moves over the horse will eventually meet up again in the back, right at the tail.”

Tails serve no practical purpose in racing. The reason horses have the long, flowing hairy tails is to keep their hairless under-parts warm in the winter and, of course, to swat flies away. In a racehorse during a race, the tail serves only as an attractive decorative banner trailing behind the horse. “I’d need data to know for sure, but I could see how a shorter tail could improve the horse’s drag coefficent,” Caruso says. “It’d be very, very slight, but it could be there.”

So you’re saying the shorter tail is why American Pharoah will win the Triple Crown, I asked him? “No, I didn’t say that, nor do I believe it,” he replied.

So the jury is still out, but according to some scientists, American Pharoah is going to win the Triple Crown because of his weird tail. If he succeeds, don’t be surprised if next year we see 20 tiny tails sticking out of the starting gate at the Kentucky Derby. It’s science, after all.


newsletter sign-up

Stay up-to-date with the best from America's Best Racing!