Interesting thing about pronghorns: According to fossils, there used to be several species, as there are now with deer. These are the only ones left. Why are they so fast? There is nothing that can come remotely close to outrunning them, even wolves. They're like Ferraris in the land of pickup trucks. Well, there also used to be cheetahs (or something very similar) in North America, and something called a short-faced bear that many paleontologists believe could run like a cheetah. So, pronghorns are a remnant of an ecology that no longer exists.
They are also known as being rather easy to hunt. (Notice I didn't tell a story about this hunt? I drove up within a couple hundred yards, got out, and shot him, all while wearing my boot cast.) They rely so much on their speed that they'll stand there and watch you, sometimes even come toward you to see what you're up to, confident in their ability to sprint out of danger. This strategy doesn't work well against firearms, obviously.
...unless they're being hunted a lot. They learn very fast, and their vision is equivalent to a human with 8x binoculars. Once they figure out that the hunt is on, they'll have you spotted from miles away, even if you're trying to be sneaky, and they're gone almost before you see them. I guess that's why they're still around.