Pygmy Rabbit Inventory at Craters of the Moon

Cirrus Ecological Solutions, LC

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. Initially, the approved methodology was to complete a burrow census and collect covariate data within the AOI, identify which burrows were occupied by pygmy rabbits using remote cameras, and to create a Resource Selection Function (RSF) to determine what habitat features pygmy rabbits are selecting for/against within the AOI (Cirrus Ecological Solutions 2020). 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. The assumption listed in Cirrus Ecological Solutions (2020) of at least 10 sampling units occupied by pygmy rabbits was not going to be met, as 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. Vegetation sampling progressed concurrently with burrow surveys. Therefore, some vegetation surveys were completed prior to the adjustments in protocols. As reported in the literature, surveys for pygmy rabbits can also be successful during the winter months, where tracks and burrow entry points are can be identified in fresh snow, and Cirrus personnel have had success with this method on past projects. Therefore, surveys were added for the winter months to further confirm whether pygmy rabbits were currently present within the AOI.

Pygmy Rabbit Inventory at Craters of the Moon

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