Pygmy rabbit inventory at Craters of the Moon National Monument and Preserve: Final report

Cirrus Ecological Solutions, LC

doi:10.36967/2297317

The Craters of the Moon National Monument has historically supported northern pygmy rabbits (Brachylagus idahoensis) within the Area of Interest (AOI). Northern pygmy rabbits have a State Rank of S3, indicating that this species is rare or uncommon, but not imperiled (IDFG 2022). Surveys were approved for the AOI to determine what habitat features pygmy rabbits are selecting for or against within the AOI to better inform future development plans. Given historical accounts of pygmy rabbit presence within the AOI, it was assumed that pygmy rabbits were present in high enough density to perform an RSF analysis. However, during the burrow survey, it became clear that adjustments were needed to account for the small number of burrows and the lack of any sign of pygmy rabbits occupying those burrows, specifically pellets. Burrows were only found in 9 sampling units, and confidence that the burrows were pygmy rabbit burrows, and not burrows of another species, was low based on observer expertise. The goal of the project shifted from identifying which habitat features pygmy rabbits were selecting for or against, to determining if any pygmy rabbits were present within the AOI. Surveys were added for the winter months to further confirm whether pygmy rabbits were currently present within the AOI. To determine if any pygmy rabbits were present within the AOI, two observers walked the AOI searching for signs of burrows or burrow complexes. A total of 35 burrow complexes were identified within the AOI. At the end of the census, a camera was placed at the opening that appeared to be the most active of each burrow complex for two weeks to maximize the chance of identifying what species were using the burrows. No pygmy rabbits were identified at any of the burrows. Twelve species were identified using at least one of the burrows or the area in front of the burrows over the course of the survey. Photo analysis confirmed that the burrows present within the AOI were not pygmy rabbit burrows, a result that was corroborated by the winter sign surveys. The size, character, and location of the burrows combined with their frequent presence at the burrow suggests that these burrow complexes were originally constructed and maintained by Columbian ground squirrels. No pygmy rabbits or signs were found by the census, remote camera efforts, or winter sign surveys.

Pygmy rabbit inventory at Craters of the Moon National Monument and Preserve: Final report

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