The Preble’s meadow jumping mouse is a member of the jumping mouse family Dipodidae with four living genera, two of which, Zapus and Napaeozapus, are found in North America, as E.R. Hall described in 1981. The three living species within the genus Zapus are the meadow jumping mouse (Z. hudsonius), the western jumping mouse (Z. princeps) and the Pacific jumping mouse (Z. trinotatus). Edward A. Preble first documented the meadow jumping mouse from Colorado in 1899. Krutzsch later described the Preble’s as a separate subspecies of meadow jumping mouse which is limited to Colorado and Wyoming in 1954. Taxonomic authorities recognize the Preble’s subspecies as one of 12 subspecies of meadow jumping mouse, as noted by D.J. Hafner and others in 1981.
There is little information on historic distribution and abundance of the Preble’s. While surveys identified various locations where the subspecies was historically present, it is now absent, as documented by T.R. Ryon in 1996. Despite numerous surveys, the Preble’s has not recently been found in the Denver or Colorado Springs metropolitan areas and is believed to be extirpated from these areas because of extensive urban development. Since at least 1991, the Preble’s has not been found in Denver, Adams or Arapahoe counties in Colorado. S.A. Compton and R.D. Hugie noted in 1993, as did T.R. Ryon noted in 1996, that its absence in these counties is likely due to urban development, which has altered, reduced or eliminatedhabitat.
The Preble’s is closely associated with riparian ecosystems that are linear in nature and represent a small percentage of the landscape. If Preble’s habitat is destroyed or modified, populations in those areas may decline or be extirpated. The main factor threatening the subspecies is the decline in the extent and quality of Preble’s habitat as was noted in the final rule for listing that was published in 1998 and reaffirmed by D.J. Hafner and others. Habitat alteration, degradation, loss and fragmentation resulting from urban development, flood control, water development, intensive agricultural activities and other human land uses have adversely affected Preble’s populations. Habitat destruction may impact individual Preble’s directly or by destroying nest sites, food resources and hibernation sites. These actions have a negative impact because they disrupt behavior, fragment habitats or create barriers to movement.
The U.S. Fish and Wildlife Service added the Preble’s meadow jumping mouse to the List of Endangered and Threatened Wildlife in 50 CFR 17.11 as a threatened species on May 13, 1998 (63 FR 26517). The U.S. Fish and Wildlife Service later designated critical habitat for the Preble’s meadow jumping mouse in 50 CFR 17.68 on June 23, 2003, and revised critical habitat for the subspecies on December 15, 2010 (74 FR 52066). Critical habitat for the Preble’s mouse includes approximately 411 miles (661 km) of rivers and streams and 34,935 acres (14,138 hectares) of lands in Colorado (75 FR 78430). Lands designated as critical habitat are under federal, state, local government and private ownership.
On average Preble’s have two litters per year, but may have up to three litters per year. An average of five young are born, but the size of a litter can range from two to eight young, as documented by D.C. Quimby in 1951 and later confirmed by J.O. Whitaker in 1963.
Preble’s are long-lived for a small mammal, surviving up to three years, in comparison with many species of mice and voles that seldom live a full year. Along South Boulder Creek, Boulder County, Colorado, seven individuals originally captured as adults were still alive two years later, having attained at least three years of age, as documented by C. Meaney and others in 2002. Although Preble’s are long-lived when compared to other small rodents, the annual survival rate is low. Preble’s survival rates appear to be lower over the summer than over the winter. Over-summer survival rates ranged from 22 to 78 percent and over-winter survival rates ranged from 56 to 97 percent, as documented by T.M. Shenk and M.M. Sivert in 1999 and later confirmed by others. Higher overwintering survival rates indicate that predation or other factors impact Preble’s during the active season.
The average weight of 120 adult Preble’s captured early in their active season prior to June 18 was 0.6 ounces (17 grams); included were 10 pregnant females weighing more than 0.8 ounces (20 grams), as noted by C. Meaney and others in 2002.
The Preble’s is a small mouse with an extremely long tail, large hind feet, and long hind legs, which enable jumping mice to make prodigious leaps. Their long tail is lightly furred and twice as long as the body. The large hind feet are three times as large as those of other mice of similar body size. Adult Preble’s are approximately 7 to 10 inches (18 to 25 centimeters) long and the tail is 4 to 6 inches (10 to 15 centimeters) long, as documented by P.H. Krutzsch in 1954 and later confirmed by J.P. Fitzgerald and others in 1994 and 2011.
During the active season, Preble’s construct day nests composed of grasses, forbs, sedges, rushes and other available plant material. Day nests may be globular in shape or simply raised mats of litter, and are most commonly above ground but may also be below ground. Day nests are typically located under debris at the base of shrubs and trees or in open grasslands, as described by T.R. Ryon in 2001. T.M. Shenk and M.M. Sivert also noted in 1999 that mice may have multiple day nests in bothand grassland communities, and may abandon a nest after approximately one week of use.
Preble’s jumping mouse is a true hibernator, usually entering hibernation in September or October and emerging the following May, after a long hibernation period of seven to eight months. Adults enter hibernation first before young of the year because they accumulate the necessary fat stores more quickly. Similar to other subspecies of meadow jumping mouse, Preble’s do not store food for hibernation. Instead, while hibernating, the Preble’s persists on fat stores accumulated prior to hibernation, according to J.O. Whitaker's observations in 1963.
Hibernacula, or hibernation nests, of Preble’s have been located both within and outside of the 100-year floodplain of streams, as noted by T.M. Shenk and M.M. Sivert in 1999 and later confirmed by both T.R. Ryon and Schorr in 2001. Those hibernating outside of the 100-year floodplain would likely be less vulnerable to flood-related mortality. Hibernacula have been located under willow (Salix spp.), snowberry (Symphoricarpos spp.), chokecherry (Prunus virginiana), skunkbrush (Rhus trilobata), sumac (Rhus spp.), clematis (Clematis spp.), cottonwoods (Populus spp.), Gamble’s oak (Quercus gambelli), thistle (Cirsium spp.), and alyssum (Alyssum spp.), according to Shenk and Sivert, 1999.
Preble’s meadow jumping mice live in well-developed, plainsvegetation with adjacent, relatively undisturbed grassland communities and a nearby water source. The well-developed, plains riparian vegetation typically includes a dense combination of grasses, forbs and shrubs; a taller shrub and tree canopy may be present, as documented by M.E. Bakeman in 1997. Bakeman and others also noted that when a taller canopy is present, the shrub canopy is often willow (Salix spp.), although other shrub species, including snowberry (Symphoricarpos spp.), chokecherry (Prunus virginiana), hawthorn (Crataegus spp.), Gambel’s oak (Quercus gambelli), alder (Alnus incana), river birch (Betula fontinalis), skunkbrush (Rhus trilobata), wild plum (P. americana), lead plant (Amorpha fruticosa), red-osier dogwood (Cornus sericea) and others may also occur.
Montane riparian areas in stands of blue spruce (Picea pungens) and quaking aspen (Populus tremuloides), with a rich diversity of shrubs, grasses and forbs in the understory, can also support Preble’s mice, as noted by A.K. Ruggles and others in 2001. Preble’s do not seem to favor a particular plant species composition, but do seem to be found more frequently in areas of high plant species richness, dense herbaceous and shrub cover, and more habitat, noted R.A. Schorr in 2001. Tributaries in these montane habitats are often narrow and located in steep slopes of dry forest with correspondingly narrow strips of riparian habitat, noted C.M. Hansen in 2006.
Preble’s have rarely been trapped in uplands adjacent to riparian areas, as documented by A.T. Dharman in 2001 and later confirmed by C.M. Hansen in 2006. However, T.M. Shenk and M.M. Sivert noted in 1999 that Preble’s feed and rest in adjacent uplands as far out as 328 feet (100 meters), beyond the 100-year floodplain. Uplands are also used for hibernation; apparent Preble’s hibernacula have been found ranging from 3.3 feet to 335 feet of a perennial stream bed or intermittent tributary, Bakeman documented in 1997 and Schorr, Ruggles and others confirmed in the early aughts. Adjacent uplands used by the Preble’s are extremely variable ranging from open grasslands to ponderosa pine woodlands, as was documented by J.G. Corn and others in 1995 and later conformed by C.A. Pague and L. Grunau in 2000.
Riparian shrub and tree cover, as well as the amount of open water nearby, are good predictors of Preble’s densities, noted G.D. White and T.M. Shenk in 2000. White and Shenk also noted that based on habitat quality, estimates of Preble’s abundance range from six to 110 mice per mile with an average of 53 mice per mile of stream. In 2001, R.A. Schorr compared habitats at capture locations on the Department of Energy’s Rocky Flats Site in Jefferson County, Colorado and the U.S. Air Force Academy in El Paso County, Colorado, revealed that academy sites had lower plant species richness at capture locations, but considerably greater numbers of Preble’s. However, the academy sites also had higher densities of both grasses and shrubs. Preble’s abundance is likely driven by the density of riparian vegetation rather than the diversity of plant species.
Ecosystem with large, flat areas of grasses.
T.M. Shenk and M.M. Sivert documented in 1999 that the diets of this species shift seasonally. After emerging from hibernation, the mice eat mostly insects and fungi and shift to fungi, moss, seeds and pollen during mid-summer, July through August. By September, the mice add insects back in their diet. The shift in diet, along with shifts in mouse movements, suggests that Preble’s may require specific seasonal diets and is may be related to the physiological constraints imposed by hibernation.
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