The Uneasy Future of Catalina Island’s Wild Bison | Science

A Bison laying down in a tropical setting

A male bison atop an arid hillside on Santa Catalina Island in California.
Alex Krowiak

In 1924, during Hollywood’s first golden age, 14 American bison arrived on Santa Catalina Island, 22 miles off the coast of Los Angeles. The animals were to appear in two movies being filmed on the island, The Vanishing American and The Thundering Herd, both adapted from Zane Grey novels. Alas, the animals didn’t make it into the former, and we don’t know if they played a part in the latter—the footage vanished long ago. But the bison remained, and some of their progeny finally made it to the big screen, in Stanley Kramer’s 1971 Bless the Beasts & Children. Descendants of the founding beasts still have star power­, helping attract hundreds of thousands of visitors every year, but perhaps their most salient role over the decades is to bedevil conservationists.

­Today, the herd presents benefits and challenges for local ecology. Visitors take bison tours, enjoy bison burgers (made from mainland meat) and quaff “buffalo milk” cocktails (featuring Kahlúa, vodka, half-and-half, crème de cacao and crème de banana—and no bison milk). Such tourism helps fund the nonprofit Catalina Island Conservancy (CIC), which controls 88 percent of the island and works to restore and protect native flora.

At its peak, in the 1980s, the herd numbered 550, but concerns about the animals’ health and ecological impact led the CIC to ship bison off the island regularly. A 2003 study found the bison were still disturbing native flora: Their shaggy coats carry plants that were imported, such as fennel, to places they wouldn’t otherwise reach, disrupting endemic species like St. Catherine’s lace. The study also found the bison were smaller and less fertile than their mainland counterparts, partly from persistent drought. In 2009, the CIC launched a contraception program for cows, rather than shipping them off the island. (During droughts, the CIC places water troughs for the animals.)

Yet population control efforts may have gone too far. By 2020, the herd was down to 100; no calves had been born since 2013, and the CIC scaled back its contraception program in 2015. Before Covid-19, the group had planned to import two pregnant females to add genetic diversity, reigniting the debate about the herd’s health and its impact on the land. Calvin Duncan, a former CIC biologist, says an increase in droughts threatens the bison, but he believes they will reproduce again when conditions improve. Juanita Constible, a consulting biologist on the 2003 study, says relocating the herd could imperil the island: Without bison grazing, wildfire intensity could increase, as the grass, unmunched, adds fuel.

Evicting the herd would also hurt island residents—4,000 or so in all—many of whom rely on bison tourism. “Wildlife management is not just about the wildlife—it’s also about the human context,” Constible says.

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