Presentation Information
[POS-38]Optimal strategy for conservation of Amami rabbits
-Should we sterilize feral cats?-
*Yoomi Hong1, Satoshi Takahashi1 (1. Nara women's university (Japan))
Keywords:
conservation,Amami rabbits,feral cats,sterilizing
Amami rabbits (Pentalagus furnessi) are a species endemic to Japan that live only in Amami Oshima Island and Tokunoshima Island, located in the south of Kyusyu Island. They are designated as an endangered species. In recent years, predation of Amami rabbits by feral cats (cats that live without human care) has become a severe problem. As a countermeasure, management plan of feral cat for preservation of ecosystem in Amami Oshima Island has been formulated, where feral cats should be captured and euthanized (killing without pain) unless they are adopted as a pet.
We examined the possibility to conserve Amami rabbits by spaying female feral cats or neutering male feral cats and releasing them into the wild without killing them. We developed a model with killing feral cats and a model with sterilizing them. We found that releasing spayed or neutered feral cats into the wild does not decrease the stationary number of Amami rabbits compared with only killing feral cats. By taking into account the reduction in birth rates due to mating with neutered males, the Amami rabbits' survival region expanded. We conclude that sterilizing feral cats is an effective measure to conserve Amami rabbits.
We extend the model to include costs of capturing and sterilizing feral cats and search the optimal strategy for conserving Amami rabbits. When feral cats could not be caught, there will be capture costs, but there will be no costs for sterilizing. When feral cats are not sterilized, we calculate the capture rate of feral cats that keep population of Amami rabbits at the target. When feral cats are sterilized, there are two candidates of the capture rate that keep the population of Amami rabbits at a target, or the capture rate that reduce the number of feral cats to zero.
Not only costs at transient but we also take into account the continuous costs. Sterilizing feral cats is advantageous when predation rate by feral cats is large and the ratio of the capture cost to the sterilize cost is large.
We examined the possibility to conserve Amami rabbits by spaying female feral cats or neutering male feral cats and releasing them into the wild without killing them. We developed a model with killing feral cats and a model with sterilizing them. We found that releasing spayed or neutered feral cats into the wild does not decrease the stationary number of Amami rabbits compared with only killing feral cats. By taking into account the reduction in birth rates due to mating with neutered males, the Amami rabbits' survival region expanded. We conclude that sterilizing feral cats is an effective measure to conserve Amami rabbits.
We extend the model to include costs of capturing and sterilizing feral cats and search the optimal strategy for conserving Amami rabbits. When feral cats could not be caught, there will be capture costs, but there will be no costs for sterilizing. When feral cats are not sterilized, we calculate the capture rate of feral cats that keep population of Amami rabbits at the target. When feral cats are sterilized, there are two candidates of the capture rate that keep the population of Amami rabbits at a target, or the capture rate that reduce the number of feral cats to zero.
Not only costs at transient but we also take into account the continuous costs. Sterilizing feral cats is advantageous when predation rate by feral cats is large and the ratio of the capture cost to the sterilize cost is large.