The Conservancy is also actively managing a herd of bison on the Island with a novel contraceptive program that is attracting the attention of wild animal managers on the mainland. The bison were first brought to the Island in 1924 for a movie. Over the years, they became an iconic symbol of the Island's culture. But with no natural predators, the herd grew to as many as 500. The Conservancy had previously conducted studies that found the Island could support only about 150 to 200 bison. To control the herd's size, the Conservancy had been periodically conducting roundups and shipping bison to the mainland.