Officials at the zoo made the tough decision to euthanize their 18-year-old Siberian tiger Tony. He was the second oldest male Siberian tiger in all of North America.
The zoo says Tony's growing health problems and worsening quality of life over the last few months made euthanasia the only humane option.
"Tony was having good days and bad days, but the bad days were becoming more frequent," said Jacqueline Jencek, DVM, chief of veterinary services at the San Francisco Zoo. "We have done everything possible to make him comfortable, but it came to a point where we didn't want to see him suffer."
Tony had been with the San Francisco Zoo since 1993, when he was just a year old.