More than a Hatrack
Zoologist Valerius Geist seems to be hung up on horns. As director of the Environmental Science Program at the University of Calgary in Alberta, he became interested in mammals with horns during his first year of field studies. He summed up some of what he has learned about the meaning of horns and antlers in a recent issue of Natural History magazine. Horns, which are permanent bone-based growths, and antlers, which are shed annually, are used for more than decorative purposes by their possessors; they can be used as weapons.
In the early 1960s, Geist spent months at a time observing the behavior of mountain goats--which is more closely related to pronghorn antelope than to true goats--in northern British Columbia. After the mating season in early winter, dominant females with kids chased other goats away from prime feeding grounds. The goats were quick to use their sharp horns in these territorial disputes, and the horns made nasty weapons. Mountain goats of both sexes pack short horns that are almost straight.
Gored goats are genuinely hurt; their wounds bleed beneath the skin, and they hobble about for days after a battle. The horns of mountain goats seem devised for causing maximum pain to a victim but also for easy withdrawal, so they don't get caught and entangle or damage the goat doing the goring.
Geist's studies and those of other zoologists generally confirm a pattern of behavior for animals possessing short, spiky horns designed for stabbing, like those of the mountain goat. Usually animals so adorned, whether tiny South American deer or big Asian antelope, defend resource-containing territories aggressively. Paleontologists suspect that now-extinct deer and antelope species probably behaved the same way, and note that big canine teeth vanished from nearly all deerlike animals as sharp antlers appeared. One type of aggressive weapon apparently was enough.
Stabbing horns are the simplest type of weaponry among horn-bearing mammals, and turned up early in their evolutionary history, a few tens of millions of years ago. But fancier antlers soon appeared. The fossil record indicates that gregarious antelope with more antlerlike horns appeared during the same epoch--the late Oligocene. Like modern herd-forming animals living in open terrain, these extinct ones probably spent most of their time together in large aggregations to avoid predators. On the early grasslands of North America just as on the tundra of northern Alaska today, any individual's odds of survival improve when a predator can take only a few victims from the periphery of a big herd.
But in closely packed herds, a wounded animal that attracted predators by blood scent or behavior puts all herd members at risk. Thus combat to settle priorities in status, mating options, or food ideally should be bloodless. The newer antlers were designed for wrestling, not bloodletting. Tines, prongs, and palms all serve as both grappling hooks and shields, ready to engage a rival's weaponry and parry his attack.
The males do sprout the fancier (and sometimes the only) antlers within a species. Elaborate antlers are the deer clan's answer to the peacock's tail. A big rack is the combat sign of a healthy, strong male, which is just what the average female deer most wants in a mate. When females also have antlers or horns, Geist notes that the female's weapons match those of the year class of male with which she is most likely to battle. The female mountain goats he watched, for example, were more likely to engage in battle with young males; the older ones knew better, and took off without combat. Reindeer cows are often hassled by two-year-old bulls, and are thus equipped with antlers the same size as those on pugnacious young males.
Knowing something of the tale told by antlers and horns makes interpreting what hangs on Alaska cabin walls wryly informative. Under that big moose rack may live a healthy big male, but don't mess with the lady sporting spikes!
