Catalina Island bison herd
The Catalina Island bison herd has existed for nearly a century. This inbred, genetically and morphologically deficient herd of American Bison, registered as privately-owned agricultural livstock in a fenced-restricted area, were supposedly imported to California's Catalina Island in 1924 for the silent film version of Zane Grey's Western tale, The Vanishing American. However, the 1925 version of "The Vanishing American" does not contain any bison and shows no terrain that resembles Catalina, according to Jim Watson, columnist for The Catalina Islander newspaper. According to Watson, an October 6, 1938 article in The Catalina Islander attributes the bison arrival to the filming of "The Thundering Herd," a silent film released in 1925.
Over the decades, the bison herd grew to as many as 600 individuals. The population currently numbers approximately 150. Biologists found that the American Bison of Santa Catalina Island are not genuinely wild, thus also not purebred; their ancestry includes genes from the domesticated cow, as well as deformities including smaller 'dwarf' size, different length of legs, jaw length overbite, low fertility, and behavioral problems (such as punctuated walking in tight circles).
The bison herd is maintained and monitored by the Catalina Island Conservancy. Since the bison are now considered naturalized immigrant animals, transported from Great Plains of the USA by train and boat, they now play a role in the cultural and economic fabric of Wrigley-family owned Santa Catalina Island Company, with profitable guided tours for paying tourists. Therefore, the Wrigley family-owned and controlled Conservancy board of directors has no plans to remove the domesticated bison from the island.
Controlling the bison population, however, remains important for Catalina's overall ecological health. In the past, bison were routinely removed and sent to the mainland to auction. In 2004, the Conservancy partnered with the Morongo Band of Mission Indians, the Tongva (thought to be Catalina's original inhabitants some 7,000 years ago), and the Lakota tribe on the Rosebud Reservation in South Dakota. A hundred bison were relocated "home" to the Great Plains. In the early 21st century however, another solution was implemented. The Conservancy initiated a scientific study that determined that a herd of between 150 and 200 would be good for the bison, and ecologically sound for the island. Beginning in 2009, the herd was given animal birth control to maintain the population at around 150 animals.
On Wednesday, August 26, 2015, a contract worker from American Conservation Experience was injured by a bison while working near Tower Peak on Catalina Island.
On Saturday, February 17, 2018, a man camping at the Little Harbor Campground was gored by a bison. 
- Vogel, AB; Tenggardjaja, K; Edmands, S; Halbert, ND; Derr, JN; Hedgecock, D (2007). "Detection of mitochondrial DNA from domestic cattle in bison on Santa Catalina Island". Animal Genetics. 38 (4): 410–2. doi:10.1111/j.1365-2052.2007.01614.x. PMID 17573784.
- Louis Sahagun (2009-11-20). "Catalina bison going on birth control". L.A. Times. Retrieved 2009-11-20.
- Ruben Vives (2015-08-26). "Bison attacks man taking photos on Catalina Island". Los Angeles Times. Retrieved 2020-06-13.