For the first time in his career, "Man vs. Wild" star Bear Grylls has failed to survive ... at the Discovery Channel -- because the network just fired him. A rep for Discovery tells The Hollywood Reporter, "Due to a continuing contractual dispute with Bear Grylls, Discovery has terminated all current productions with him." Sources tell THR, the relationship came to a screeching halt after 37-year-old Grylls refused to participate in two mystery projects he was contracted for. Grylls originally partnered with Discovery in 2006 when "Man vs. Wild" premiered on the network. So far, no word on Grylls' next move ... though it will probably somehow involve him drinking his own urine.