In this case not the result of a sporting obsession, but a collector's enthusiasm. Deformutilation explains:
Between Bozeman and Butte in the Big Sky country of Montana, lives a man with an obsession. His name is James Phillips, but most everybody in these parts knows him as Antler Man. Since he was a boy living in a homemade trailer in the Gallatin Canyon, Phillips has hiked the area’s big tracts of public land to hunt for antlers dropped by whitetails, mule deer, elk, and moose. In a half-century of scouring hillsides, washes, and ridgelines for a glint of bone, he has amassed more than 15,000 antlers, which he displays in a 30x64-foot building he calls The Horn Shed. Over the years he built freestanding archways of antler and progressively larger buildings to showcase his finds. When he began building his current shed from reclaimed lumber, he designed it to display the most horns in the best possible way: a cathedral of bone...Mr. Phillips' website has lots more information.
While a few have come as gifts, a handful in trade, all the others he packed out on his back, without the aid of ATVs or horses, on dawn-to-dusk hikes or multi-day trips that take him miles into steep back country.