Nutrient and demographic characteristics of sagebrush prefentially foraged on by pygmy rabbits (Brachylagus idahoensisi) in Northern Utah

Background/Question/Methods

The pygmy rabbit (Brachylagus idahoensis), the world’s smallest rabbit, has a limited distribution due to its year round dependence on sagebrush (Artemisia tridentata) for food and shelter.  As much as 99% of the pygmy rabbit diet consists of sagebrush. With such a specialized diet, obtaining the full spectrum of needed nutrients can be difficult. In this study, we sought to determine whether pygmy rabbit foraging patterns were driven by the nutritional quality of sagebrush. Sagebrush samples were taken from burrow areas at 5-20m in 5m increments. Demographic data (height, major and minor crown) was collected for each sagebrush sampled, and sagebrush were labeled as foraged or non-foraged based on evidence of herbivory by pygmy rabbits.  Sagebrush samples were then analyzed for nutrient content using near-infrared spectroscopy for percent dry matter (DM), crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), and total digestible nutrients (TDN). The area of study is on U.S. Bureau of Land Management (BLM) land near Woodruff in northeastern Utah. This study was initiated in winter 2013 and is ongoing.

Results/Conclusions

Pygmy rabbits preferentially foraged on sagebrush that was closer to burrows (5.8+1.4m from borrow for foraged vs 15.8+1.1m from burrows, p<0.001).  Foraged sagebrush was 38% taller than non-foraged sagebrush (p=0.004) and provided more than twice the amount of cover (p=0.002).  Also, analysis of the protein and the % neutral detergent fiber (NDF) content in relation to the distance from the burrow showed a significant positive correlation between % NDF and distance from the burrow (R²=.4001, p=0.0002) and a significant negative correlation between total protein content and distance from the burrow (R²=0.1318, p=0.04). Results of the study suggest that proximity and size of sagebrush are important drivers of the foraging patterns of pygmy rabbits.  The fact that sagebrush closer to burrows were higher in protein and lower in fiber may indicate that pygmy rabbit burrows promote the growth and nutrient density of sagebrush.  Further research is currently underway to determine if the burrowing habits of pygmy rabbits may be increasing the nutrient content of sagebrush in close proximity to burrow sites.