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The bizarre treat Golden Gate Park’s bison get once a year

One of Golden Gate Park's resident bison on Jan. 25, 2023. | Morgan Ellis/The Standard

Every year when it comes time to kick old Christmas trees to the curb, Golden Gate Park’s bison are just getting ready to celebrate.

As a seasonal addition to San Francisco Zoo’s enrichment program, the gentle giants are gifted unsold Christmas trees to romp around with every year. And it’s not just the bison—other animals like the zoo’s steer, chimpanzees and orangutans love to get in on the holiday fun, too.

Golden Gate Park's resident bison play with Christmas trees in their enclosure. | Courtesy San Francisco Zoo & Gardens

“They’ll nibble on them a little bit, but primarily they’re going to play with them,” said Debra Marrin, the zoo’s director of training and behavioral husbandry. “They’re going to toss them around with their horns. They’re going to rub on them so they can feel the different texture.”

Basically, the bison use the trees as giant toys, sparring partners and the occasional snack. The zoo provides environmental enrichment materials to stimulate play behaviors that the bison would instinctively do in the wild.

“When we have animals that we’re taking care of, we want to provide them opportunities to display and practice natural behaviors,” Marrin said. “Animals like to have things where they can investigate and exert control over elements in their environment.”

Bison have a highly developed sense of smell, so the trees also offer a pleasant sensory experience, similar to how humans enjoy them.

READ MORE: Meet Udo: San Francisco Zoo’s New Pygmy Hippo

Hundreds of orphaned firs—usually more than the zoo can take—are donated annually by Christmas tree farms in the city. When placed in the bison enclosure, they can entertain them for up to several weeks, according to Marrin.

The zoo has to be pretty picky about the trees it gives to its animals, though. It only accepts donations of trees that went unsold at lots to avoid any chemical treatments that may be on the trees in people’s homes, like flocking. So, bad news for locals a little late to wrap up their holiday season. And you definitely should not toss your Christmas tree into the bison paddock. 

Golden Gate Park's resident bison play with Christmas trees in their enclosure. | Courtesy San Francisco Zoo & Gardens

“The enrichment makes the guests’ interactions even more positive and connects them to the animals even more because it shows a little bit of their personality,” said Marrin. “Anytime they come by and see active animals, of course that’s way more exciting than watching an animal take a nap.”

And be sure to stop by the paddock again around Halloween when the bison get pumpkins to roll around and smash.

Morgan Ellis can be reached at