Five out of 169 fertile California condor (Gymnogyps californianus) eggs laid in captivity have exhibited chondrodystrophy, a lethal form of dwarfism. Pedigree records indicate that this chondrodystrophy, like similar conditions in chickens, turkeys and quail, is probably inherited as an autosomal, recessive allele. We estimate that the frequency of this putative allele is about 9%. This high frequency is probably due to a founder effect. We consider three management options for the allele: ignoring it, eliminating it by selection and minimizing its phenotypic manifestation by avoiding matings between possible carriers. We recommend minimizing its phenotypic expression because an unacceptably large proportion of condors (up to 78 out of 146) would be prevented from breeding under a selection strategy designed to eliminate the allele. We predict that many captive populations will prove similar to the California condor population in that it will prove inadvisable or impractical to select against one or more deleterious alleles detected in the population.
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