San Francisco’s bison are going extinct. One of the six remaining buffalo was put down recently due to old age, according to zoo officials. With a shortfall in the city budget that's going to mean cuts for public safety or programs that serve the poor, the thousands of dollars the city may have to shell out to rescue the shrinking herd is no laughing matter. The last bill paid by tax payers to accommodate the herd was not cheap: $1.2 million for upgrading their home. Two rich donors have signaled they may help cover the city’s costs to breed them or buy more. Can San Francisco’s bison survive the economic slump?