A contraceptives program launched on Catalina Island in 2009 was found more effective in controlling the bison population compared with relocation.
The program has enabled wildlife biologists to keep levels of population that are beneficial not only to the herds of bison but also to the island’s ecological health.
It’s a long-term program," said Calvin Duncan, a wildlife biologist who co-led the contraceptives effort, to The Salt Lake Tribune. "The conservancy is looking to find a balance. The bison have been really ingrained into the culture and the residents love them. Hopefully, this is something that can be considered in other bison herds."
The bison were first introduced to Catalina Island back in 1924 as part of a movie which never made it to the big screen. However, they became like a historical icon that reflects the island’s wildlife. As years passed, the herd grew bigger and has reached over 600. This created an urgency to remove them off the island.
The bison are usually shipped by the conservancy to Native American reservations and auction houses. Otherwise, they are being rounded up for the administration of large doses of hormones as a type of contraception.
The new program is one form of immune-contraception which uses porcine zona pellucid (PZP). The latter is then applied in a very little dosage which can be administered using either a dart or a syringe.
The contraceptive has been used to control fertility among white-tailed deer, wild horses, and those animals in the zoo. The females are given two doses while on their initial year of the program. Then, they are given just a single dosage in every year that follows.
Aside from being more cost-effective, the program is also more efficient for the biologists as there’s no more need for them to corral huge animals or locate them across the island. Currently, the population is stabilized and has been reduced to have 159 animals.
The study was presented at the International Conference on Fertility Control in Wildlife.
