dependent on the date of birth. Young from early litters grow larger due to a longer developmental period prior to their first winter. The mortality of adults is highest in late winter and early spring. Green and Flinders reported a maximum estimated annual adult mortality of 88% in Idaho. Juvenile mortality was highest from birth to 5 weeks of age. Pygmy rabbits may be active at any time of day; however, they are generally most active at dusk and dawn. They usually rest near or inside their burrows during midday. Habitat Pygmy rabbits are normally found in areas on deep soils with tall, dense sagebrush which they use for shelter and food. Individual sagebrush plants in areas inhabited by pygmy rabbits are often 6 feet (1.8 m) or more in height. Extensive, well-used runways interlace the sage thickets and provide travel and escape routes. Dense stands of big sagebrush along streams, roads, and fencerows provide dispersal corridors for pygmy rabbits. The pygmy rabbit is the only leporid native to North America that digs burrows. Juveniles use burrows more than other age groups. Early reproductive activities of adults may be concentrated at burrows. When pygmy rabbits can utilize sagebrush cover, burrow use is decreased. Pygmy rabbits use burrows more in the winter for thermal cover than at other times of the year. Burrows are usually located on slopes at the base of sagebrush plants, and face north to east. Tunnels widen below the surface, forming chambers, and extend to a maximum depth of about . Burrows typically have 4 or 5 entrances but may have as few as 2 or as many as 10. In Oregon, pygmy rabbits inhabited areas where soils were significantly deeper and looser than soils at adjacent sites. Site selection was probably related to ease of excavation of burrows. In areas where soil is shallow pygmy rabbits live in holes among volcanic rocks, in stone walls, around abandoned buildings, and in burrows made by badgers (Taxidea taxus) and marmots (Marmota flaviventris). Some researchers have found that pygmy rabbits never venture farther than from their burrows. However, Bradfield observed pygmy rabbits range up to from their burrows. Some areas inhabited by pygmy rabbits are covered with several feet of snow for up to 2 or more months during the winter. During periods when the snow has covered most of the sagebrush, pygmy rabbits tunnel beneath the snow to