In December, staffers at the Oakland Zoo opened the mail to find an unexpected gift: a $1 million anonymous donation. The gift, which came from a donor or donors with the San Francisco Foundation’s Serendipity Fund, will go into the zoo’s general fund.

Emma Lee Twitchell, who oversees fundraising at the zoo, says she was “absolutely surprised and delighted” with the unexpected donation. She said she was out touring the zoo with visitors when zoo president and CEO Dr. Joel Parrott found the gift in the mail. “We were both really excited,” she said, “just overwhelmed by the generosity and the fact that it was an anonymous gift.”

The $1 million donation is the zoo’s largest-ever anonymous gift. “I doubt there are many organizations that have had that pleasure,” said Twitchell, who also called the size of the donation “not typical.”

Twitchell said that the Oakland Zoo sometimes receives anonymous gifts, and tries to respect the wishes and intent of the donors. In this case, even Twitchell doesn’t know the identity of the donor or donors, except that the donation came through the Serendipity Fund, which was set up by the San Francisco Foundation to facilitate anonymous charitable donations. Other groups that have received donations through the Serendipity Fund include the Oakland-based Family Builders foster care organization and the Women’s Cancer Resource Center.

Twitchell said that “human nature is trying to figure out the puzzle” of where the gift came from, but that her job is to understand what prompted the gift and how to best acknowledge it. The $1 million will be directed towards the Zoo’s general operations fund, an unrestricted pot of money that the zoo can use for any purpose. The zoo’s board will make decisions about where that money will ultimately be directed, but hasn’t yet, she said.

Twitchell said it would be premature to discuss which animals or projects will benefit from the gift. “We are always looking to make everything better,” Twitchell said. “There are several areas that we can look at and determine where the best use is.” For example, she said, “Maybe it’s a new piece of medical equipment … or something that allows the animal keeper to have better access. It’s those kind of things that we look to.”

The Oakland Zoo—home to more than 660 species, including lions, chimpanzees, macaws, and recently, a giraffe—sits on a 525-acre site on East Oakland’s Knowland Park. In November, a county-wide tax measure that would have provided the zoo with more than $112 million over the next quarter century failed at the polls. It garnered 62 percent of votes in support, but required a two-thirds majority. The zoo has long planned a controversial expansion into Knowland Park, which critics have said could harm the habitat of threatened native species. Measure A1’s opponents voiced concerns that the tax would be used to fund that expansion, a claim denied by zoo officials.

Some of the zoo’s plans for the new year include renovating its veterinary care center and building an education and conservation center, as well as acquiring and caring for new animals.

Twitchell said that the $1 million gift wouldn’t “necessarily” stimulate fundraising from other donors, but said that the anonymous donor’s confidence in the zoo “validates the work of this organization.”