Notes

This facility has housed a minimum of four walruses. 

The first known individuals were a pair of calves, believed to likely be two females captured in May of 1968 and housed at the Biological Sonar Laboratory. It was published on September 17th of 1968 that the duo would be temporarily exhibited at the park up to the 22nd. 

It was then announced on November 28th of the same year that 17-month-old Igor would be the Zoo's first permanent walrus resident; he was joined in early June of 1969 by Helga, the final known walrus.

It was mentioned on January 22nd of 1970 that one walrus had died of a tusk infection -- the preventable loss was recounted during planning talks for a fundraising event at the San Francisco Zoo, intended to raise money for a veterinary hospital and veterinarian at the zoo.

I have thus far been unable to find any reference to walruses remaining in the Zoo's collection beyond 1969 - 1970. 

References

• 1968-Sep-17. San Francisco Chronicle. New at the Zoo. Retrieved from newspapers.com.

• 1968-Nov-28. Contra Costa Times. Walrus Comes To SF Zoo. Retrieved from newspapers.com.

• 1968-Nov-29. San Francisco Examiner. Walrus Is New Zoo Resident. Retrieved from newspapers.com.