On March 19, 1998, at 1000 hours Pacific standard time, a Cessna TU206F, N9674G, experienced a loss of engine power on the takeoff initial climb and made a forced landing in a box canyon 2 miles west of the Avalon, California, airport. The aircraft sustained substantial damage. The private pilot/owner was not injured. Visual meteorological conditions existed for the local personal flight and no flight plan was filed. The flight departed Mammoth, California, on the morning of the accident and was scheduled to terminate at John Wayne Airport, Santa Ana, California. The National Transportation Safety Board made repeated unsuccessful attempts to contact the pilot. Information regarding the pilot and aircraft were obtained from the insurance adjuster. In the pilot's written statement, he had departed from Mammoth at 0730 the morning of the accident with a stop at Catalina to retrieve a file. The pilot stated that the aircraft had been topped off the day before the accident. He stated that during the preflight at Mammoth he noticed some rodent droppings in the aircraft, and some papers and a blanket had been chewed on. The pilot stated that during the flight to Catalina no mechanical anomalies were noted with the aircraft. After landing at Catalina, the pilot retrieved his file and asked a mechanic to look at the rodent droppings for identification. During the discussion the mechanic saw a squirrel exit the left side of the aircraft. The pilot reported that he conducted another preflight with no malfunctions noted and departed for John Wayne Airport. The pilot stated that after passing through 1,700 msl and past the departure end of the runway, the engine quit as if "someone had turned off ignition key." He attempted a restart without success and made a forced landing. The pilot reported to the Los Angeles County Sheriff's Department that after takeoff the engine began to sputter, he switched fuel tanks, and attempted to restart the engine. A certified Federal Aviation Administration repair station examined the engine and noted debris in the flow divider, fuel screen, and metering valve. According to the fuel log obtained from Sky Trek aviation at Mammoth airport, the aircraft had been refueled with 46.7 gallons on March 18th. During the recovery of the aircraft, recovery personnel noted animal feces present in the aircraft. The ignition switch was removed for an inspection and the p-leads, as well as the airspeed indicator line, had been chewed. The Safety Board conducted an inspection of the ignition switch and found no abnormalities.