Run. Mountain goat attacks are rare, and unprovoked fatal gores are virtually unheard of. The animals normally become aggressive only when they feel trapped, so in a confrontation with one of them, your best tactic is to flee. You won't be able to outrun a mountain goat, but it probably wouldn't pursue you very far. If a goat does come after you, try taking an aggressive posture and pelting your attacker with rocks. Although an attempted stoning by would-be rescuers didn't seem to scare Saturday's murderous goat, a similar approach tends to work pretty well against ungulates. Throwing rocks at mountain goats technically contravenes National Park Service rules against harassing wildlife, but expulsion from the park beats being gored.
If the rocks don't scare off the animal, you're in serious trouble. Your last resort in hand-to-hoof combat is to grab the goat by its horns. Mountain goats can whip their heads around faster than other ungulates like caribou and elk, and their horns are razor-sharp. Indian tribes of the Pacific Northwest used the horns as weapons, and mountain goats have managed to puncture the hearts of grizzly bears. Researchers occasionally resort to horn-grabbing when a goat unexpectedly arouses from anesthesia or was never fully under in the first place. (It's hard to spend a career studying the animals without suffering a nasty gash or two.) Mountain goats are powerful enough to break any human's grip, so you won't be able to hold on very long. If you can stall the attack for long enough, someone might come to your rescue—preferably with a gun.
Most mountain goats roam the vast open spaces of Alaska and Canada, where they tend to have very little contact with humans. On flat ground, they usually won't let people get within 500 yards. (The animals are a bit less skittish on rocky cliffs, where they have a natural advantage.) In national parks where the mountain goats are an introduced species, they have become so accustomed to people that they'll let hikers come within a few feet.
Although attacks against humans are few and far between, mountain goats are among the most aggressive ungulates toward their own species. When individuals are grouped together, they display, charge, and engage in mini-duels four or five times per hour. Females are typically more aggressive than males.
It's hard to know what motivated Saturday's attack. Veterinarians have taken tissue samples to check for illnesses, but they probably won't reveal anything useful. Herbivores like mountain goats are susceptible to rabies, but infections are rare. The blood samples won't uncover brain diseases that could have altered behavior. It may be that the goat in question happened to have a very aggressive personality. Or it could have had identity issues: After attacking the hiker on Saturday, the goat stood over his body for nearly an hour. This sort of dominance display is common among bison, which pose over younger rivals they have killed to impress the rest of the herd, but is virtually unheard of in mountain goats. In general, bison are much more likely to gore tourists.
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Explainer thanks Steeve D. Côté of Université Laval and Joel Berger of the University of Montana.