Pygmy Rabbit Ecology: Habitat, Distribution, Population Trends
Photo of pygmy rabbit

The pygmy rabbit fills a crucial ecological role in the sagebrush community. USGS researchers have been studying the species’ distribution in Wyoming, their specific habitat needs, and how energy development may affect their habitat and distribution.

Project Partners

Bureau of Land Management

Wyoming Game and Fish Department

Wyoming Natural Diversity Database

The Nature Conservancy

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Contact Steve Germaine

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Identifying and Mapping Crucial Pygmy Rabbit Habitat

The pygmy rabbit belongs to a unique community of animals that depend on sagebrush habitats of the interior American West. By digging underground burrows, pygmy rabbits aerate the soil and recycle nutrients, and their burrows provide refuges for many vertebrate and invertebrate animals. Pygmy rabbits also serve as important prey for birds and mammals. Although, the pygmy rabbit clearly fills a crucial ecological role in the sagebrush community, more information is needed about the species’ distribution in Wyoming, their specific habitat needs, and how energy development may affect their habitat and distribution. Wyoming Game and Fish Department lists pygmy rabbit as a Species of Greatest Conservation Need.

Sagebrush habitat has been reduced by half since European settlement, and much of what remains has been fragmented by development and degraded by invasions of non-native plants and altered wildfire patterns. This has created concern about pygmy rabbit population trends. Given the extent of current and potential future energy development in the WLCI region, conservation planners seek information about what makes high-quality pygmy rabbit habitats, where those habitats are located, and how energy development affects the amount and quality of habitat.

 

Key Findings

  • Pygmy rabbit distribution models developed by The Nature Conservancy and Wyoming Natural Diversity Database correctly classified 61−63% of the habitat in the WLCI as suitable for pygmy rabbits. However, when we combined the models, only 11% of the area was classified as suitable and 47% classified as unsuitable. The models disagreed about how to classify the remaining 42%.
  • Both models classified pygmy rabbit habitat more accurately in undeveloped areas than in developed areas. Habitat classification success declined steeply in gas fields where road density exceeded 5 kilometers per square kilometer.
Study Objectives
 
The ultimate goals of this work are to support conservation planning by modeling and mapping characteristics and locations of high-quality pygmy rabbit habitat pygmy rabbit distributions and population dynamics.
  • Conduct field surveys of pygmy rabbits in the WLCI region for validating the accuracy of current models of pygmy rabbit distribution and habitat occupancy.
  • Develop a new model that increases the accuracy of predicting pygmy rabbit habitat occupancy.
  • Assess effects of land-use changes and habitat quality on pygmy rabbit population dynamics, dispersal, and genetic diversity.
  • Relate pygmy rabbit occupancy to LiDAR sagebrush structure data.

 

Map showing areas of agreement and disagreement between existing pygmy rabbit occupancy models.

Areas of spatial agreement (blue and beige) and disagreement (pink and green) between the 2008 Wyoming Natural Diversity Database and 2009 The Nature Conservancy pygmy rabbit species-distribution models for southwestern Wyoming (Click to enlarge).

Pygmy rabbits are usually found in relatively tall, dense stands of predominantly big sagebrush that offer excellent cover from weather extremes and birds of prey. Sagebrush is also a primary food source for these animals, particularly in winter. Because pygmy rabbits dig their own burrows, they require soils loose enough to dig into but cohesive enough to resist burrow collapse. Because of these specific habitat requirements, pygmy rabbit distribution within the sagebrush ecosystem is irregular and patchy across the landscape, with small “colonies” of rabbits inhabiting irregularly distributed patches of tall, dense sagebrush. Movements among suitable sagebrush patches are necessary for successful breeding, dispersal, and maintenance of genetic diversity. Throughout their range, pygmy rabbit populations have declined as sagebrush habitats have been reduced and fragmented. 
 
Since 2008, USGS researchers have worked with scientists from the Wyoming Natural Diversity Database (WYNDD) to collect information on the presence/absence of pygmy rabbits. We have sampled 850 sites (550 by USGS, 300 by WYNDD). Additionally, we sampled nearly 200 sites throughout southwestern Wyoming to validate two pygmy rabbit distribution models for Wyoming: one each developed by WYNDD and The Nature Conservancy. 
photo of biologists preparing to trap pygmy rabbits
Photo of biologist holding pygmy rabbit fitted with GPS tracker.

Pygmy rabbits are usually found in relatively tall, dense stands of predominantly big sagebrush. They require soils loose enough to dig into but cohesive enough to resist burrow collapse.

USGS field technicians looking for pygmy rabbits or signs of recent pygmy rabbit occupancy. We used this data to validate two existing models for predicting pygmy rabbit distribution in Wyoming.

Adult pygmy rabbits were fitted with global positioning system units to track their movements.