California island’s bison benefitting from birth control

AVALON, Calif. — Bison birth control has proved a boon for a rare herd off the Southern California coast and the island where they roam.

A new study by the Catalina Island Conservancy to be published this month shows that a contraceptives program launched in 2009 for the island’s bison has proven to be a more effective and humane way of controlling their population than the previous practice of relocation, the Daily Breeze reported Sunday.

The bison, commonly called American buffalo, are descendants of 14 animals that were shipped to the island in 1924 to make a Western film. They weren’t used in the movie and were simply left behind.

At one point, as many as 600 of the shaggy beasts roamed the island 25 miles off the Los Angeles coast. There were about 350 in 2003 when a study found that they had poor nutrition and health.

To control the numbers, bison were once shipped out for slaughter then later sent to Indian reservations for breeding.

But those who tend the herd now say that the birth control vaccine known as PZP has proven the best way to do that.

“We learned that if we chose to have a herd, we should reduce the number to 150 since it’s better for the bison and it’s better for the habitat,” said Ann Muscat, president and CEO of the conservancy, a nonprofit group that owns much of the island. “They’re of great cultural and historical value to the island and we’re very pleased that the program is working out as well as it is.”

PZP is derived from pig eggs and must be renewed annually via dart or syringe. It has little effect on the bison’s lives beyond reducing their reproduction.

“The bison are doing what they were doing before and it’s not causing any difference in hormones or behavior,” said Calvin Duncan, a wildlife biologist who helped lead the contraception effort.

The population has been successfully stabilized at 159 animals.

“Hopefully, this is something that can be considered in other bison herds,” Duncan said. “The unique part of Catalina is that it’s a living laboratory.”