Until recent decades, little was known about the pygmy rabbit, a small rabbit facing big threats in the Great Basin and the neighboring intermountain areas it inhabits. Weighing in at only one pound, this tiny rabbit depends on underground burrows in native sagebrush ecosystems, which are being reduced by wildfire, invasive species, climate change and development. These pressures have led the pygmy rabbit to be petitioned for listing under the Endangered Species Act. Across the pygmy rabbit’s range, universities, nonprofits, and state and federal agencies have formed robust research partnerships driven by a shared goal to understand the resilience of this unique species to ongoing and future changes.

Source: National Park Service

Though much has been learned about this species in the last two decades, increasing variability in winter temperatures and snow have prompted new research questions about how pygmy rabbits are responding to changing environmental conditions. Adaptive capacity — the ability to cope with or adjust to changing climatic conditions — is a key factor in understanding the pygmy rabbit’s vulnerability, and therefore, in managing its survival and persistence in the future. A new suite of projects supported by a collaboration across university, state, federal and NGO partners, including the NW CASC, seeks to better understand the adaptive capacity of pygmy rabbits. 

As part of this suite of projects, the NW CASC is supporting work led by University of Idaho’s Dr. Timothy Link, Dr. Matt Falcy, and Dr. Janet Rachlow, to understand how changing snowpack, soil temperature and moisture conditions will affect burrow habitats and how pygmy rabbits respond to these changes. Since pygmy rabbits are sensitive to both hot and cold temperatures, they depend on burrows in their sagebrush ecosystems to regulate their body temperature. In the winter, they occupy existing tunnels underground and also make new tunnels in the snow. Snow provides insulation from the cold as well as cover from predators as they travel through their snowy tunnels to feed on sagebrush plants. As snowfall becomes less consistent with climate variations, insufficient snow could mean that pygmy rabbits need to spend more energy staying warm and may experience more predation traveling to sagebrush plants to eat.

Source: Timothy Link

Pygmy rabbits are found in a diverse range of winter climates, from warmer and drier areas with limited snowfall, to colder, mountainous areas that receive substantial snow. The project team is currently examining how changing snow conditions will affect underground burrow habitat across this range of climates. Research team member and University of Idaho doctoral student Jacob Russell is studying the local conditions (i.e., microclimates) of pygmy rabbits’ underground burrows at diverse sites across southern Idaho, chosen to represent the different climates across their range. He’ll then model how these burrow microclimates will change with shifting snow conditions into the future to understand the sensitivity and resilience of these microclimates to climate conditions. Link explains, “One of the approaches that Jacob is taking is to use our measured data and project it forward in time with detailed numerical models to assess how variations in temperature and precipitation will affect these burrow microclimates.”

In the next phase of this project, Jacob will connect his findings about changing burrow conditions to models of pygmy rabbit habitat use, energy balance and predator avoidance, to understand how the species may adapt its behavior to cope with projected environmental extremes. By understanding what these animals are actually experiencing in their burrows and how they are behaving within them, we can understand the microhabitat characteristics that might help support their adaptive capacity into the future.

This project is partnering closely with the Bureau of Land Management, which oversees the land on which many of the research sites are located, as well the Idaho Department of Fish and Game (IDFG), which is helping inform Jacob’s research along the way. Jacob has been presenting his progress at meetings for the IDFG, the USGS Cooperative Fish and Wildlife Research Unit and the Idaho Chapter of the Wildlife Society.

Thanks to the robust partnerships and collaboration supporting this work, the findings from these complementary projects will paint a clearer picture of pygmy rabbits’ adaptive capacity that can help managers decide how best to steward this species into the future.

Along with this NW CASC-supported project focused on pygmy rabbit burrow habitat, two complementary projects are exploring additional factors that influence the adaptive capacity of pygmy rabbits. University of Idaho doctoral student Fiona McKibben’s research is focused on where pygmy rabbits are distributed on the landscape as well as their behaviors, while fellow doctoral student Illaria Bacchiocchi is studying genetic diversity across populations to determine whether some populations have genes that better help them adapt to changing conditions.

This suite of projects, which intersect and leverage one another in multiple ways, are receiving support from the Bureau of Land Management, the U.S. Fish and Wildlife Service, U.S. Geological Survey, Idaho Department of Fish and Game, the Montana Department of Fish, Wildlife and Parks and the Jackson Fork Ranch. Thanks to the robust partnerships and collaboration supporting this work, the findings from these complementary projects will paint a clearer picture of pygmy rabbits’ adaptive capacity that can help managers decide how best to steward this species into the future.