A famous and tragic lobo pioneer was euthanized due to the infirmities of age in late May 2009, at the California Wolf Center, where he had been living in retirement since December 4, 2002. M166, or Rio, as he was known at the Wild Canid Survival and Research Center where he was born on April 27, 1994, was one of the first lobos released into the wild in 1998. He fathered the first wild born Mexican wolf pup in the United States in at least a half-century–a pup that was lost after his mother was illegally shot.
Rio was the alpha male of the Campbell Blue pack and was the father of wolf F511, or BrÃ¼nnhilde, whose image graced a prize-winning poster from the Arizona Game and Fish Department. He was the offspring of Francisco (M60) and Sheila (F37), and the grandpup of M2 (Don Diego), one of the five lobos captured in Mexico by Roy McBride. His great-grandmother was Nina (F5), the only wild-caught female founder of the McBride lineage.
Rio had a total of four mates, and was released and re-released into the wild a total of four times. His first mate was illegally shot. His second mate was killed by a mountain lion, and a third was recaptured for nuisance behavior. He and his fourth mate, F592, both began killing livestock after scavenging on carcasses of cattle they did not kill. F592 later became the first reintroduced Mexican wolf shot by the project for depredations.
Rio was permanently removed from the wild to spend his later years in seclusion at the Julian, CA, facility. His sister and littermate Aspen (F168), who spent time in the wild as alpha female of the Gavilan pack before being recaptured for killing livestock in early 2000, remained with him to the end and helped him cope with the deterioration of his eyesight.