On July 8, 1996, at 0015 mountain standard time, a Mooney M20C, N6715N, owned and operated by the pilot, collided with elk during landing rollout on runway 24 at the Payson Airport, Payson, Arizona. The airplane was substantially damaged. Neither the private pilot nor passenger was injured. Visual meteorological conditions prevailed, and no flight plan was filed for the nighttime flight which originated the previous evening from Bullhead City, Arizona, at 2215. The pilot reported to the Payson city police department that during the landing flare he observed a herd of elk near the approach end of the runway. He flew over the herd and landed on the remaining runway. During rollout, the airplane collided with two elk in another herd. The right main landing gear assembly broke off and exited through the upper surface of the wing. The airplane slid to a stop without further mishap. The pilot reported that he ties down his airplane at the Payson airport. He was aware that elk and other animals had unrestricted access to the runway environment since no fence surrounded the airport. Airport personnel reported that elk are occasionally observed on the airport and runway. A notice indicating that occurrence was in effect and had been published in the current FAA Airport/Facility Directory. An officer from the Payson police department reported detecting the odor of an intoxicating beverage on the pilot's breath. The pilot reported that about 1830 the previous evening he drank "a couple of beers" while in Laughlin, Nevada. The police officer administered a field sobriety and a portable breath test (PBT) on the pilot at 0304. The PBT sample produced results at the 0.03 percent level.