When the young antelope are about three weeks old they appear to have full use of their legs and usually follow the mother in feedings and fights. At this time numbers of mothers and youngsters collect and run together. They are thus enabled to give mutual aid and to withstand coyotes and other enemies better. Sometimes under dangerous conditions the young are left behind while some of the mothers go for water, and on their return the remaining ones go. Just why this mutual aid is not practised while the young are almost helpless is not clear.
In early autumn all ages and sexes unite and commonly run together, often in large flocks, throughout the winter. The youngsters often play together. Frequently one of the males is the lively leader of twenty or thirty. At other times the old antelopes play, go through a series of marches and countermarches. They race back and forth and over short circles. When thus engaged they commonly have sentinels posted on the outskirts.
Most other animals appear to forget possible enemies while playing, but the nervous antelope, with big open spaces round it, appears never to be quite in repose.
Depending upon speed rather than upon stealth, fighting ability, or concealment, as a means of escaping enemies, and living in the plains with a magnificence of unobstructed distances, it has learned to be watchful, to use sentinels, and to flee even when danger is afar.
Usually when the antelope lies down it selects a spot well away from any ravine, bluff, willow clump, or sagebrush thicket that could conceal an enemy or that would enable an enemy to approach it closely unseen.
Under most conditions the female appears to be the acknowledged leader. In the majority of instances in which I have watched moving flocks of antelope—fleeing small numbers or a number of alarmed antelope preparing to move—it was under female leadership.
The pronghorn lives in a home territory. This I think is rarely more than six or eight miles in diameter. If pursued by man, dogs, or wolves it is likely to run in great circles, keeping within the bounds of home territory. Most antelope are not migratory, but in a few localities the flocks make a short migration. For winter they may travel to a more broken locality, one that gives some shelter from the wind and contains spaces off which the wind sweeps the snow.
The antelope makes long leaps but not high jumps. I watched an antelope that had been separated from the flock hurrying to rejoin it. In its way was a line of willows along the dry, shallow water channel. This willow stretch was not wide nor high. A deer would have leaped it without the slightest hesitation. The antelope went far round and jumped wide gullies, but made no attempt to leap this one low line of willows. Being a plains animal, knowing but little of cliffs and timber, it has not learned high jumping.
For ages the antelope was thickly scattered over the Great Plains and the small parks of the West, Northwest, and Southwest. Fifty years ago they were numbered by millions. The present antelope population numbers not more than 15,000. Howard Eaton tells me that years ago he sometimes saw several thousand in a single day. Once when a boy I saw at least a thousand in a North Park, Colorado, flock.
A few are now protected in the national parks and in private antelope reserves. But they are verging well toward extermination. Rarely does the antelope thrive in captivity. Apparently the food ordinarily fed it in captivity does not agree with it.