Environment & Science

Of bison, birth control and an island off Southern Calif.

Bison have been roaming the Santa Catalina Island since the 1920s. At one time they numbered more than 600.
Bison have been roaming the Santa Catalina Island since the 1920s. At one time they numbered more than 600.
Kirk Siegler/NPR

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In an open-aired Jeep, it's a bone-jarring ride into Santa Catalina Island's vast interior. The dirt road winds and climbs, twists and turns, climbing 2,000 feet up.

From there, the deep blue of the Pacific Ocean comes back into view, and if you squint, you can see downtown Los Angeles 30 miles off on the horizon.

Some days, you can also see wild bison.

"This is a really common place to see a bison, you'll see them in groups, and then solitary males, very frequently in this stretch of road," says John Mack, chief conservation officer for the private Catalina Island Conservancy, which manages most of the land here.

As if on cue, a couple minutes later, a lone male bison comes into view, standing stoically atop a ridge of a hill blanketed with scrub oak trees.

"It's, well, an interesting thing to see," biologist Julie King says from the back seat.

King is in charge of managing the 150 wild bison roaming the island. They're by no means native. Fourteen of the animals were brought here in 1924 by a Hollywood crew for a film shoot. The movie never got made, and the bison were never returned to the wild.

"Logistically, probably, it was too difficult, and I'm guessing they thought bison were a lot like cattle, that you could turn them loose and herd them fairly easily," King says.

You can't. They jump fences. Or plow right through them. And with no natural predators, their population exploded. At one point in the 1980s, there were more than 600 here. That's when the conservancy sprang into action. There was some hunting. But mostly the group paid to ship excess bison, by barge, over to the mainland and eventually to tribes in South Dakota.

But lately, King and her team have discovered a new, cheaper solution: contraception.

Each spring, the team sets out into Catalina's backcountry on foot, armed with dart guns and a birth control vaccine called porcine zona pellucida, or PZP.

"You have to be careful, because they will charge," says King, who adds she's had that happen on more than one occasion after successfully hitting a female cow with the PZP-filled dart.

But she says the risk is worth it, because the contraception program is yielding some impressive early results. Since it began three years ago, the conservancy has managed to bring the herd down to 150 animals; the number they consider sustainable.

No more shipping, no more hunting and no more culling.

That's starting to get people's attention in places where bison are a problem, like Yellowstone National Park.

"The problem is reproduction, you can remove animals 'til the cows come home and you haven't solved the problem," says Jay Kirkpatrick, director of the Science and Conservation Center at Zoo Montana.

Kirkpatrick says all eyes are on the work that's being done with bison on Catalina Island. He hopes the early successes will bolster support for a similar solution in Yellowstone. The herd there is also too big for the park, and right now bison that roam outside and onto land grazed by cattle are sometimes shot.

Kirkpatrick says the PZP vaccine has been successful on female bison in zoos for twenty years. The privately owned Catalina Island is the first place contraception is being used on bison in the wild.

Even though bison aren't supposed to be on Catalina Island, biologist Julie King says removing the animals all together is off the table.

They're big business. Each summer, thousands of tourists climb into those Jeeps for a day trip into the interior.

"So many people come here because it's closer than going to South Dakota or to Montana to see bison," King says.

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