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Siberian tiger; Endangered species; Wildlife recovery; Animal populations


The wild population of Siberian tigers (Panthera tigris altaica) is estimated at about 300 in six separate populations. Since an effective population size of at least 500 is necessary for long-term survival and evolution, and since the wild populations are not going to be able to expand in their natural habitat, it is evident that a captive breeding program is necessary for sustained preservation of this form. There are 1000 living Siberian tigers in zoos; only three outside of Russia are wild-born. About 250 are in North American zoos. Although about 68 wild-caught animals have been brought into zoos, six animals account for 69% of the founder representation of the living population. The population is inbred with mean F = 0.113, and 70% of the population has a positive inbreeding coefficient. Inbreeding in tigers results in a decrease in life span in animals living longer than one year. The genetically effective population size (Ne) is about 0.35 of the census size (N) when it could be 2N. This is a result of unequal family sizes of both male and female parents. About 50 North American zoos are participating in a tiger Species Survival Plan (SSP) formulated by the American Association of Zoological Parks and Aquariums. An 11-person propagation committee was elected by the institutional representatives to work with the Species Coordinator in developing and implementing the plan. The breeding strategy includes agreements to maintain an effective population of250 animals, to maintain a demographically stable population and to provide for maximum retention of available genetic diversity by maximizing the Ne in relation to and minimizing inbreeding. These objectives will be accomplished by introducing new founder stock; equalizing representation of founders; equalizing family sizes, with each animal contributing to the next generation; avoiding inbreeding; avoiding phenotypic selection; producing 10 to 15 litters per year, and removing from the SSP population all animals reaching the age of 13 years if they have made their genetic contribution. A detailed plan specifying by zoo, for each animal, recommended animals to be bred and the year for the matings has been through three revisions and is being used by participants. The plan also identifies animals that are not to be bred for the SSP and the dates all animals are to be considered surplus to the SSP.

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