Uulu (OOH'-loo), a 545-pound female, died Friday at the age of 36.
The zoo says her health had rapidly declined because of congestive heart failure and old age.
The zoo rescued Uulu when she was 3.
The San Francisco Chronicle says she'd been scheduled for euthanasia for repeatedly rummaging through a town dump in Manitoba, Canada.
The zoo says Uulu had a curious nature and loved to dig in the dirt, which turned her white fur brown.
In February, she frolicked in 10 tons of snow and ice brought in to celebrate International Polar Bear Day.