Managing the herd of bison on 76 square mile Santa Catalina island

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Bison on Catalina Island

Santa Catalina is a 76 miĀ² island, 22 miles south-west of Los Angeles in the Pacific Ocean. It’s described as a paradise of soaring mountains and lush grasslands. There are few cars and many gift shops selling bison trinkets because the island is known for its bison population.

Bison on Catalina Island

Bison jump and run as a bison is hit with a dart. Photo by Brad Graverson/The Daily Breeze)

The species was brought to the island in 1924 as props for a Hollywood film. Fourteen of the animals were left behind when the crew went home to mainland America. They bred, as they would do, to create a population of 350. Although it is said that they are much smaller than their mainland counterparts and are unhealthy with relatively low reproduction rates. Comment: this points to inbreeding causing inbreeding depression and sterility.

A scientific study recommended herd reduction because at 350 it was too large for the island as they were causing damage to the ecology in various ways including damaging plant species.

A population size reduction programme was commenced by the Catalina Island Conservancy, the charity which owns 90% of the island. They are aware that tourists who come to the island want to see bison running wild rather than being fenced in. But it appears that they struggled in managing the herd because once they had started to sterilise them in 2009 (to shrink the herd’s size to 150) there’s been no new bison born on the island for the past seven years and so the herd has dropped in size to 100.

Now they have to reintroduce bison to the island from the mainland to allow them to start creating babies again. Some biologists have opposed the plan to import pregnant females from the Laramie Foothills bison conservation herd in Colorado.

They argue that by adding more bison it won’t necessarily mean that tourists can see them because they tend to congregate in remote areas of the island where consumers don’t go. Also they say that the underlying cause of the shrinkage in the herd size has not been dealt with. I have provided my opinion above but of course that is the opinion of a layperson not a qualified scientist.

Critics of the plan to import bison say that it would have been better to reduce the mule deer population size which currently stands at 2800. The mule deer is a more destructive animal they argue.

Map showing location of the island

The address of the island is: Santa Catalina Island, California 90704, USA