Recovery Plan for the Columbia Basin Distinct Population Segment of the Pygmy Rabbit (Brachylagus idahoensis)

Current Status:
We listed the Columbia Basin distinct population segment of the pygmy rabbit (Brachylagus idahoensis) as an endangered species under an emergency regulation in 2001 (USFWS 2001), and fully listed it as endangered in 2003 (USFWS 2003). The current recovery priority number for the Columbia Basin pygmy rabbit is 6 (USFWS 2010a). The Washington Department of Fish and Wildlife began a captive breeding program for the Columbia Basin pygmy rabbit in 2001 (WDFW 2001a), and developed an intercross breeding strategy in 2003 (WDFW 2003). Intercross breeding was conducted to help facilitate genetic restoration of the Columbia Basin pygmy rabbit due to severe inbreeding depression in the purebred captive animals, and is considered essential for recovery efforts (USFWS 2011b). Intercross breeding was accomplished through carefully controlled matings between the founding purebred Columbia Basin animals and pygmy rabbits of the same taxonomic classification from a discrete population in Idaho. The last known wild subpopulation of pygmy rabbits within the Columbia Basin was extirpated by early 2004, although other wild subpopulations may still exist on lands that have not yet been surveyed. In March of 2007, 20 captive-bred, intercrossed pygmy rabbits were reintroduced to habitats historically occupied by the species in the Columbia Basin of central Washington. These captive-bred animals experienced very high mortality over the first several weeks following their release and none were believed to have survived through the spring of 2008. Following the development and implementation of appropriate adaptive management measures, reintroduction efforts were resumed in the summer of 2011. The new measures that have been implemented include additional releases of the captive-bred intercrossed pygmy rabbits, the capture and translocation of wild pygmy rabbits from populations outside of the Columbia Basin for inclusion in the reintroduction program, initiation of partially controlled field-breeding efforts, and improved protective measures during releases. As these new measures have been implemented, the need for continuing captive breeding efforts has steadily diminished, and captive breeding operations at three cooperating facilities were discontinued by the end of July 2012.

Distribution and Habitat:
The pygmy rabbit has been present within the Columbia Basin ecosystem, a geographic area that extends from northern Oregon through central Washington, for over 100,000 years. This distinct population segment of the pygmy rabbit, which is the subject of this Recovery Plan, is believed to have been separated from the remainder of the species’ range for at least 10,000 years, as suggested by the fossil record and genetic analyses. Museum specimens and sighting records indicate that the Columbia Basin pygmy rabbit likely occurred in portions of six Washington counties during the first half of the 20th century, including Douglas, Grant, Lincoln, Adams, Franklin, and Benton.

Pygmy rabbits occur in the semiarid shrub steppe biome of the Great Basin and adjacent intermountain regions of the western United States. Within this broad biome, pygmy rabbits are typically found in habitat types that include tall, dense stands of sagebrush (Artemisia spp.), on which they are highly dependent to provide both food and shelter throughout the year. The pygmy rabbit is one of only two native rabbit species in North America that digs its own burrows and, therefore, is most often found in areas with relatively deep, loose soils that allow burrowing.

Threats to Recovery:
Large-scale loss and fragmentation of native shrub steppe habitats, primarily for agricultural development, likely played a primary role in the long-term decline of the Columbia Basin pygmy rabbit. However, it is unlikely that these factors alone directly influenced the eventual extirpation of all known subpopulations from the wild. Once a population declines below a certain threshold, it is at risk of extirpation from a number of influences including chance environmental events (e.g., extreme weather), catastrophic habitat loss or resource failure (e.g., from wildfire or insect infestations), predation, disease, demographic limitations, loss of genetic diversity, and inbreeding. At the time of our emergency listing action in 2001, the Columbia Basin pygmy rabbit was imminently threatened by its small population size, loss of genetic diversity, and inbreeding depression, coupled with a lack of suitable, protected habitats in the wild. To varying degrees, all of the above influences continue to impact the Columbia Basin pygmy rabbit and, in combination, have resulted in the population’s endangered status.

Recovery Strategy:
A phased approach for recovery planning has been prescribed by this Recovery Plan. The three general phases are: 1) removal or abatement of imminent threats to the population and the potentially suitable shrub steppe habitats in the Columbia Basin; 2) reestablishment of an appropriate number and distribution of free-ranging subpopulations over the near term; and 3) establishment and protection of a sufficiently resilient, free-ranging population that would be expected to withstand foreseeable long-term threats. This recovery strategy is oriented to dynamic adaptive management of the Columbia Basin pygmy rabbit and its habitat, consistent with the Service’s Strategic Habitat Conservation process, which calls for an iterative process of biological planning, conservation design, conservation delivery, and monitoring and research. The biological planning and conservation design set forth in this recovery plan lay out the criteria for recovery and identify localities for implementing actions, while the recovery actions describe a process for implementing conservation on the ground, outcome-based monitoring to assess success, and ongoing assumption-driven research to test biological hypotheses important to management. To facilitate such a strategy, specific near-term (i.e., 2012 â€" 2021) and more general long-term objectives and criteria have been established. In addition, revised implementation schedules will be developed, as necessary, to reflect the knowledge gained, accomplishments met, potential future constraints encountered, and consequent refinements to near-term recovery objectives, criteria, and/or actions as recovery progresses.

Recovery Goal and Objective:
The goal of this Federal recovery effort is to reclassify the species as threatened and, ultimately, remove it from the Federal List of Endangered and Threatened Wildlife and Plants. This will require that threats to free-ranging Columbia Basin pygmy rabbits are sufficiently abated to ensure a high probability of the population’s persistence within its historical distribution over the foreseeable future. The long-term recovery objective is to increase the number, distribution, and security of free-ranging subpopulations of the pygmy rabbit within the Columbia Basin so that the recovery goal may be met.

Recovery Actions:

• Action 1: Manage partially controlled field-breeding for the Columbia Basin pygmy rabbit.
• Action 2: Survey for, monitor, and assess free-ranging Columbia Basin pygmy rabbits.
• Action 3: Reestablish free-ranging Columbia Basin pygmy rabbit subpopulations within their historical distribution.
• Action 4: Protect free-ranging Columbia Basin pygmy rabbits.
• Action 5: Manage habitats at recovery emphasis areas to support stable, self-sustaining subpopulations of free-ranging Columbia Basin pygmy rabbits.
• Action 6: Pursue conservation agreements for the Columbia Basin pygmy rabbit with landowners and managers of intervening properties within the population’s historical distribution.
• Action 7: Exchange information with stakeholders and the general public to address concerns and increase support for Columbia Basin pygmy rabbit recovery efforts.
• Action 8: Secure funding for Columbia Basin pygmy rabbit recovery efforts.
• Action 9: Revise the Federal Recovery Plan to facilitate implementation of adaptive management measures considered necessary to achieve the phased recovery strategy.

Date of Recovery:
It is not currently possible to estimate a date of recovery for this population as relatively few, if any, Columbia Basin pygmy rabbits currently survive in the wild as established populations. Only about 100 intercrossed individuals have been recently reintroduced to habitats historically occupied by the species within the Columbia Basin, and the success of future translocation, field-breeding, and reintroduction efforts cannot yet be accurately predicted.

Total Estimated Cost of Recovery:
It is not currently possible to estimate the total cost of recovery. The estimated cost to implement all recovery actions described in the Implementation Schedule over the next 10 years is $1,079,000. It may be assumed that continued, intensive management would be required for at least the following decade, at roughly half the cost.

Table 1. Recovery Action Time and Cost ($000’s)