A bison named "Last Cow" died Monday in San Francisco's Golden Gate Park, San Francisco Zoo officials announced today.
The female American bison was 22 years old and the oldest bison at the park, according to zoo officials.
Members of the San Francisco Zoological Society cared for her and staff from the zoo had been monitoring her for several months due to her old age, officials said.
Bison have a life expectancy of 25 years.
She was living in a meadow at Golden Gate Park and was an original descendant of bison that was a birthday gift in 1984 to then-mayor and Sen. Dianne Feinstein from her husband, Richard Blum.
Six 3-year-old bison were brought to the same meadow in 2011 and remain there today, zoo officials said.
The San Francisco Recreation and Parks Department maintains the meadow and the San Francisco Zoological Society provides veterinary services to the bison.
"We take special care to accommodate the needs of our geriatric animals," Graham Crawford, San Francisco Zoo chief of veterinary services, said in a statement.
"Her longevity can be attributed to the great care provided by her animal care staff," Crawford said.
Bison were first brought to Golden Gate Park in 1891, when they were at risk for extinction, zoo officials said. The thriving herd gave birth to 100 calves as part of a nationwide captive breeding program.
Today there are more than 200,000 bison in existence protected in their natural environment at Yellowstone National Park.