Preble's Meadow Jumping Mouse

Zapus hudsonius preblei

Description

Preble's meadow jumping mouse (Zapus hudsonius preblei ) is a small rodent in the family Zapodidae and is one of 12 recognized subspecies of the species Z. hudsonius, the meadow jumping mouse. The family Zapus consists of small to medium-sized mice with long tails and long feet adapted for jumping. Z. hudsonius is greyish to yellowish-brown in color with an indistinct mid-dorsal band of darker hair and paler sides, large hind legs and hind feet, and a sparsely haired tail that accounts for more than 60% of the total length. Preble's jumping mouse is dull in color, ranging from clay to tawny-olive with a mixture of black hair forming poorly defined dorsal band; the sides lighter, from clay to cinnamon-buff; the lateral line is distinct and clear ochraceous-buff; the belly is white, sometimes with a faint wash of clear ochraceous-buff; the bicolored tail is brownish to light brownish-black above, grayish-white to yellowish-white below. The subspecies are distinguished from one another in part by the characteristics of the skull. There is a similarity of appearance between the Preble's meadow jumping mouse and Z. princeps, which also occurs in portions of Colorado and Wyoming. In general, Z. hudsonius may be distinguished from Z. princeps by average external size and cranial size. Preble's also has a less pronounced mid-dorsal band, smaller average total length, and a skull that is small and light with a narrower braincase and smaller molars. Since coloration of the mid-dorsal band and total length are not definitive characteristics, skull measurements are most useful for positive identification. Ranges of the Preble's and Z. princeps are not known to overlap in Colorado but the relationships between respective ranges in Wyoming is less clear.

Behavior

Preble's meadow jumping mouse has not been studied as extensively as other subspecies of Z. hudsoniushave been studied elsewhere. Preble's is thought to be similar to other Z. hudsonius in patterns of diet, behavior, breeding, and habitat utilization. In general, Z. hudsonius subsists on seeds, small fruits, fungi, and insects, and hibernates from October to May. It is adapted for digging, creates nests of grasses, leaves, and woody material several centimeters below the ground, and is primarily nocturnal or crepuscular, but can be observed during daylight. During the breeding season (June to mid-August), females typically have two to three litters of five to six young per litter. Z. hudsonius hibernates approximately seven months of the year in an underground burrow that it excavates itself. The month of May marks the beginning of the active period for Preble's. Breeding probably occurs soon after emergence. Adults begin hibernation in early September, while juveniles enter hibernation from mid-September to late October. Adults reach approximately 20% body fat before going into hibernation. Little information exists on Preble's meadow jumping mouse food preferences. It has been speculated that Preble's may need an open water source to fulfill dietary water requirements.

Habitat

Z. hudsonius occurs mostly in low undergrowth consisting of grasses, forbs (herbaceous plants other than grasses), or both, in open wet meadows and riparian corridors, or where tall shrubs and low trees provide adequate cover. In addition, Z. hudsonius prefers lowlands with medium to high moisture over drier uplands. Z. hudsonius avoids the sparse vegetation that is generally associated with low moisture habitats and is most common in lush vegetation along watercourses or in herbaceous understories in wooded areas. Proximity to water may be the most important factor influencing habitat selection and utilization by Z. hudsonius. Preble's meadow jumping mouse appears to be primarily dependent on riparian shrublands, and on mesic mixed grasslands that are adjacent to shrublands and in or near complex riparian communities with multi-strata woodland and herbaceous species, including coyote willow, western snowberry, and choke cherry. Preferred habitat seems to be dense vegetation that presents burrowing or nesting opportunities.

Distribution

Preble's meadow jumping mouse may never have been widespread in the period since western settlement. In 1972, it was described as poorly known in Colorado and apparently nowhere abundant. The apparent local extirpation of Preble's from historically occupied sites in Colorado and Wyoming, and the difficulty in finding it in patches of apparently adequate but fragmented habitat isolated by human land uses, suggests a decline in populations of Preble's in recent decades. Preble's is thought to exist currently in seven counties in Colorado and two in Wyoming. It is not known to be present in three other counties in Colorado and three counties in Wyoming where it was previously documented.

Annual studies have taken place at Rocky Flats, Colorado since the discovery of the Preble's meadow jumping mouse there in 1991. Recent populations have been reported in all four major drainages within the Rocky Flats buffer zone. During the 1995 field season, 61 Preble's were trapped at Rocky Flats, bringing the total number of individual mice trapped since 1991 to 161. Spring1996 trapping studies at Rocky Flats, designed to document emergence from hibernation, resulted in 29 captures of Preble's. Preble's has also been captured in Jefferson, Douglas, and El Paso counties, Colorado.

In Wyoming, Preble's meadow jumping mouse has been recently documented in Laramie and Albany counties. The Wyoming Cooperative Research Unit successfully captured two Preble's on F. E. Warren Air Force Base.

Threats

Preble's meadow jumping mouse, historically a rare mammal, has declined. Seven counties in Colorado and two in Wyoming are known to support Preble's populations. Riparian habitats required to support Preble's have been severely modified or destroyed by human activities in many areas east of the Colorado Front Range and in southeastern Wyoming. As human population increases, the loss and modification of riparian habitat continues. Existing regulations have proven to be inadequate to protect Preble's, as witnessed by its apparent decline and the continued destruction and modification of its habitats.

The importance of "late season obesity" (the buildup of fat reserves) in meadow jumping mice and its positive correlation to hibernation survival, post-hibernation development, and successful re-production has been well documented. Preble's meadow jumping mice entering hibernation with low fat reserves are less likely to survive the winter or to breed successfully the following spring. Late season grazing of Preble's habitat, as well as mowing or burning, could adversely affect Preble's by reducing the availability of food resources essential for buildup of fat reserves.

Some researchers hypothesize that overgrazing by livestock may be an important cause of the decline of the Preble's meadow jumping mouse. In southeastern Wyoming almost all private land of appropriate topography and hydrology to support Preble's habitat is heavily grazed by livestock, and overgrazing is the most significant factor in reducing habitat for Preble's.

City of Boulder Open Space lands endured intensive grazing, farming, or haying regimes until they became part of the City of Boulder Open Space system. Grazing and haying continue on sites supporting the Preble's meadow jumping mouse, largely as land management tools.

Human development has produced profound changes in the hydrology of streams flowing east from the Colorado Front Range. Riparian habitat on which the Preble's meadow jumping mouse depends is in turn dependent on surface flows and groundwater. Water for commercial and residential use has reduced and fragmented riparian habitats used by Preble's.

Water diversions and associated land use changes can impact Preble's meadow jumping mouse habitat directly, as well as through hydrological alterations to Preble's habitat located downstream.

While Rocky Flats supports one of the largest known populations of Preble's meadow jumping mouse and has served as a refuge for Preble's, the future conservation of Preble's at this site is uncertain due to possible impacts to occupied habitats. Preble's meadow jumping mouse habitats at Rocky Flats could be impacted by the Department of Energy's planned hazardous contaminant cleanup. An additional threat is potential disruption of the current hydrology by mining operations. There are proposals to expand existing commercial sand and gravel extraction and processing activities in the Rock Creek drainage both outside and within the boundary of Rocky Flats. Mining impacts are significant and, unlike some other human uses, cause permanent changes to Preble's habitat. Mining also targets gravel deposits that may provide key hibernation sites.

Residential and commercial development, accompanied by highway and bridge construction, and instream alterations to implement flood control, directly remove Preble's meadow jumping mouse habitat, or reduce, alter, fragment, and isolate the habitat. Roads, trails, or other linear development through Preble's habitat may act as barriers to movement; acceptable dispersal corridors linking patches of Preble's habitat may be critical to its conservation.

Development and heavy use of trails within occupied Preble's meadow jumping mouse habitats may impact the species by destroying its habitat, nests, and food resources, or by disrupting behavior. Recreational trail systems have been established or are proposed along many riparian corridors within Preble's range. Heavily used recreational trails currently exist on City of Boulder Open Space-lands, including sites that support Preble's.

Habitat alteration may encourage growth of both invasive weeds that degrade Preble's habitat, and weed control programs that would remove cover and thereby impact Preble's habitat.

The Preble's meadow jumping mouse, as well as other native rodents, carries parasites and diseases that may reduce vigor, curtail reproductive success, and cause death. There is no evidence whether or not any epizootic disease has caused significant impact to Preble's. While plague is regularly found in other rodent species within Preble's range, its impact to Preble's populations is not known.

Predation on the Preble's meadow jumping mouse has always existed as a naturally occurring association between predator and prey. Human development may have altered this relationship. Free-ranging domestic cats may locally present a problem to Preble's.

Use of pesticides and herbicides has undoubtedly increased across known Preble's meadow jumping mouse range as human land use has intensified. These chemicals could directly poison Preble's or may be ingested through contaminated food or water. Specific impacts to Preble's from pesticides and herbicides are not currently known. Intensive human development creates a range of additional environmental impacts (including but not limited to noise, and the degradation of air and water quality) that could alter Preble's behavior, increase the levels of stress, and ultimately contribute to loss of vigor or death of individuals, and extirpation of populations.

Conservation and Recovery

Colorado Division of Wildlife Regulations (Chapter 10, Article IV) classifies Z. hudsonius as a nongame species. This designation means that permits must be obtained for take of Preble's meadow jumping mouse related to scientific, educational, or rehabilitation purposes. Preble's is currently under consideration for endangered species designation in Colorado. In Wyoming, the Wyoming Game and Fish Department has classified Z. hudsonius as a nongame species protected under Wyoming Game and Fish Department.

Of note is the 1997 creation of a Preble's Meadow Jumping Mouse Working Group, organized by the Colorado Department of Natural Resources to initiate a collaborative planning process designed to produce a legally and scientifically sound approach to conservation of Preble's.

The Preble's meadow jumping mouse occurs on lands administered by the U. S. Air Force, Department of Energy, U. S. Forest Service, Colorado Division of Wildlife, Colorado State Parks, Boulder County, Jefferson County, City of Boulder, and on private lands. For Federal lands where Preble's occur, appropriate land management is required by law to evaluate potential impacts to Preble's that may result from activities they authorize or permit.

Appropriate Federal agencies are required to approve and oversee any activities that include: removing, thinning or altering vegetation; implementing livestock grazing management that alters vegetation during warm seasons; construction of roads or access along or through riparian areas; channelization and other alteration of perennial and intermittent streams and their hydrological regimes for flood control and other water management purposes; permanent and temporary damming of streams to create water storage reservoirs or deviate the stream's course; human activities in or near Preble's meadow jumping mouse habitats; construction of residential, commercial, and industrial developments, including roads, bridges, public utilities and telephone lines, pipelines, and other structures; bioremediation and hazardous materials management, containment, and cleanup efforts such as those at Rocky Flats; and, sand and gravel and other types of mining activities within or upstream of Preble's meadow jumping mouse habitats.

Contacts

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
P. O. Box 25486
Denver Federal Center
Denver, Colorado 80225
http://www.r6.fws.gov/

U. S. Fish and Wildlife Service
Colorado Ecological Services Field Office
Denver Federal Center
P. O. Box 25486
Denver, Colorado 80225-0486
Telephone: (303) 275-2370
Fax: (303) 275-2371

Reference

U. S. Fish and Wildlife Service. 13 May 1998. "Final Rule to List the Preble's Meadow Jumping Mouse as a Threatened Species." Federal Register 63 (92) 26517-26530.