On October 26, 2005, approximately 1545 mountain standard time, a Piper PA-18-150, N4055Z, piloted by a private pilot, was substantially damaged when it ground looped during landing near Cortez Municipal Airport (CEZ), Cortez, Colorado. Visual meteorological conditions prevailed at the time of the accident. The personal flight was being conducted under the provisions of Title 14 CFR Part 91 without a flight plan. The pilot and passenger were not injured. The local flight originated from the pilot's private airstrip, near CEZ, approximately 1430. According to a telephone interview with the pilot and the accident report he subsequently submitted, he was attempting to land at his home when he noticed a horse near the approach end of the runway. He elected to land long to avoid a horse but then realized insufficient runway remained. He attempted a go-around and added full power but could not arrest the sink rate. He decided to land the airplane on the runway remaining. He landed with power applied in a nose high attitude right at stall speed. The left wing struck the ground, causing the airplane to rotate 180 degrees to the left and dragging the right wingtip dragged along the ground. The pilot said he was unfamiliar with mountain flying conditions in Cortez, Colorado, (5,918 feet msl) as he had done most of his flying near sea level in Alaska. He said he had just filled the fuel tanks to capacity, and the extra weight of the fuel and the rear seat passenger made the airplane heavier than what he was accustom. He also said there was a 5 knot tailwind during the landing. Postaccident examination disclosed a broken left wing spar. The right wingtip was scratched. Density altitude at the time of the accident was calculated to be 7,741 feet mean seal level (msl).