JOHANNESBURG — When Cecil the lion’s carcass was finally found after he was lured out of a Zimbabwe wildlife reserve to be killed by an American hunter, it was a headless, skinless skeleton the vultures had been picking at for about a week. Conservationists decided the most natural thing was to leave the bones where they were for hyenas to finish off, said Brent Stapelkamp, a lion researcher and part of a team that had tracked and studied Cecil for nine years. Stapelkamp darted Cecil and put his last GPS collar on in October.