DRAFT Periodic Status Review for the Pygmy Rabbit (2024)

Pygmy rabbits (Brachylagus idahoensis) occur mainly in the Great Basin and some of the adjacent intermountain areas of the western United States, including Washington, Oregon, California, Idaho, Montana, Wyoming, Colorado, Nevada, and Utah. Columbia Basin pygmy rabbits are geographically and genetically discrete from the remainder of the taxon and this population is significant due to the unique ecological setting (i.e., geologic, climate, soil, and vegetation community) in which it occurs. For these reasons, the Columbia Basin pygmy rabbit population was designated as a Distinct Population Segment (DPS) for protection under the Endangered Species Act.

Pygmy rabbits are sagebrush obligates. Within their broad geographic range, pygmy rabbits have a patchy distribution and are found where sagebrush occurs in tall, dense clusters and soils are sufficiently deep and friable to allow for burrowing. Dense stands of sagebrush provide pygmy rabbits with year-round food and shelter; native, perennial grasses and forbs provide an important food source beginning in spring and especially in summer and fall; deep, friable soils allow them to construct burrows for shelter and to give birth to their young.

Historical documented locations of pygmy rabbits indicate a prior distribution that included portions of five Washington counties. By 1997, pygmy rabbits were known to occur at only six isolated populations in pockets of suitable habitat in Douglas County (five sites) and northern Grant County (one site); three of these sites had fewer than 30 active burrows. By March 2001, five of the six populations had disappeared, and pygmy rabbits were known to occur only at the Sagebrush Flat Wildlife Area. A captive breeding program began in 2002 and was effective in managing the genetic characteristics of the population and maintaining the captive population, but ultimately could not produce enough kits to support large-scale reintroductions. In 2011, the recovery effort transitioned from off-site captive breeding to semi-wild breeding within large enclosures located within shrubsteppe. Additionally, breeding enclosure populations were augmented with wild pygmy rabbits that were translocated from Great Basin populations between 2011 and 2013 to bolster genetic diversity and sustain breeding enclosure populations. Kit production and rabbit releases increased substantially through 2015 before dramatically declining in 2016 due to disease (coccidia) in enclosures. To reduce disease and weed infestations in permanent breeding enclosures the recovery effort in 2017 began transitioning to a smaller, mobile breeding enclosure design. A second augmentation to breeding enclosure populations occurred in the spring of 2020 with wild rabbits translocated from Great Basin populations. In 2020, the Pearl Hill fire setback recovery efforts with the burning of all suitable habitat in the Burton Draw Recovery Area and the resulting loss of all rabbits in enclosures and in the wild. Currently, two small, wild populations occur in the Beezley Hills and Sagebrush Flats Recovery Areas.

Large-scale loss, degradation, and fragmentation of native shrubsteppe habitat likely played a primary role in the long-term decline of the Columbia Basin pygmy rabbit. By the mid-1900s, large portions of shrubsteppe habitat within the Columbia Basin were converted to agricultural crops or urban and rural development. Remaining stands of sagebrush are affected by other, often interacting, factors including historical overgrazing by livestock, invasion by non-native plant species, and altered fire frequency. Disease was initially a limiting factor in breeding enclosure populations but now seems to have been alleviated with the transition to a new breeding enclosure design. Fire remains a significant threat to pygmy rabbit recovery.

The Columbia Basin pygmy rabbit population has not met population or secure habitat criteria for down-listing from its current state endangered classification. The population remains small and its distribution in the wild is extremely limited. It is therefore recommended that the pygmy rabbit remain a state endangered species in Washington.