Completion Form

2024

This funding supported efforts to investigate the distribution of pygmy rabbits in Box Elder and Rich Counties. It supplemented other funding which took a statewide approach.

We built a sampling frame based on models of the 4 core population areas, Rich Co (NRO), Box Elder Co (NRO), West Desert (SRO), and Fishlake (SRO). Random cells (250m x 250m) were sampled by area search and any positives initiated searches of the next nearest cells. Random cells yielded no positive results so were abandoned in favor of resampling all known and historic areas within these population cores. The models were too simplified and overpredictive, and much better refinement is needed for these models to be useful. Prior sampling has been largely effective in finding pygmy rabbits and we are reasonably sure we have a mostly complete knowledge of where pygmy rabbits occur. Area searches consisted of looking for burrows and pellets. Only 2 burrows would be marked and recorded within the grid cell, so the cell may contain other unmarked burrows but would be marked as active at the cell level. Burrows were assessed for use, by presence of pellets (fresh or aged), and level of burrow maintenance (open vs debris or spider web presence), or whether burrows were collapsed. When sign at a burrow was inconclusive about which species was using it, or about activity level, trail cameras were set for at least 4 nights to determine burrow status. All data was entered into a joint database (statewide, and gathers data collected by partnering agencies like BLM) using a Survey123 form. Current or recent sign of pygmy rabbits was recorded at 723 locations.

Project goals were to assess the current status of historically identified pygmy rabbit sites. We also used habitat modeling and surveys to investigate other sagebrush areas an better define distribution. The habitat models were overpredictive and would need to be refined to be useful for management decisions. As such, random sampling based on these models did not identify any rabbit locations (previously known or unknown). Monitoring needs to focus on resampling of known areas to determine persistence through time. New locations were still identified, but not from the models and only by observation while traveling between survey locations. Through searches in historical areas, we were able to confirm persistent pygmy rabbit populations in all four core areas. This is especially important as rabbit hemorrhagic disease was documented in 2021 and there was fear it could extirpate populations.

Specifically for Northern Utah, we found robust pygmy rabbit populations in Rich County and Box Elder County. This work confirmed and expanded the known distribution in both areas.

Kimberly Hersey

01/23/2025 15:00:29