Increased egg infertility associated with translocating inbred takahe (Porphyrio hochstetteri) to island refuges in New Zealand

摘要

The takahe (Porphyrio hochstetteri) is a highly endangered flightless rail, endemic to New Zealand. Since 1984, a total of 24 takahe have been translocated from a small, alpine population of approximately 120 in Fiordland and successfully established on four predator-free lowland islands with introduced pasture grasslands. However, island takahe produce fewer juveniles per egg due to hatching failure being twice as high as it is in the natural population in Fiordland. A comparison among several small, inbred populations of New Zealand birds indicated those that are the result of translocations to new habitat types (takahe and kakapo Strigops habroptilus), suffered much higher rates of egg infertility than birds that have remained within their natural habitat range. For takahe, whether breeders had been translocated as juveniles or had been raised on the islands was a poor predictor of reproductive success. The coefficient of inbreeding was high for island takahe but high infertility and low juvenile productivity were features of breeding pairs whether parents were related or not. However, this result might be expected if takahe were already inbred before they were translocated to the islands. If high egg infertility is a consequence of an inbred population being translocated to a new or different habitat, then poor breeding success is something that managers may have to live with in the short term until there is local selection for better breeders. In more general terms, the results of the study have implications for the successful translocation of individuals from inbred populations.