Modeling for threatened and endangered species management: The Columbia Basin pygmy rabbit and the greater sage grouse in Washington

Threatened and endangered species are the hallmark of the biodiversity crisis of our times. The listing of species by governments prompts research and management to prevent further declines and to conserve and restore populations at sustainable levels. The shrub-steppe of eastern Washington hosts two species at risk, the Columbia Basin pygmy rabbit (Brachylagus idahoensis) and the Greater sage-grouse (Centrocercus urophasianus). Conservation and restoration requires tools to assess risk of population decline or extinction for species and to strengthen restoration plans that must integrate many forms of knowledge from science to expert opinion to local ecological knowledge. Computer models are powerful tools for these purposes. Software for population viability analysis has been specifically developed to make risk assessments. Other computer modeling programs such as system dynamics are adaptable to the task of integrating knowledge, simulating systems and providing a method for testing and supporting management decisions. As well, many general statistical methods and models can be used to analyze raw data on species and systems of concern. The Columbia Basin pygmy rabbit exists only in a captive breeding program, which was unable to produce sufficient numbers of rabbits to support a reintroduction effort in 2007 and 2008. Population viability analysis was used to determine where the demographic bottleneck exists in the population and to explore where research efforts should be concentrated. It also defined a risk of extinction to the population if harvest for reintroduction was continuous over the several years most likely required to restore rabbits to the wild. Correlation and regression tree modeling was used to compare the survival of an experimental pygmy rabbit reintroduction that occurred in 2004 with the first actual release of captive reared animals back into a portion of their historical range. Population viability analysis was also performed for a remnant population of sage-grouse in eastern Washington. It was coupled with a system dynamics model that incorporated the land use complex and habitat suitability of remaining sage-grouse habitat in Washington. The system dynamics model was a participatory modeling exercise with a local conservation district designed to provide them with a land use planning and wildlife management tool.