U.S. Fish & Wildlife Service Preble’s Meadow Jumping Mouse (Zapus hudsonius preblei) Surveys on the Rocky Flats National Wildlife Refuge (2014-2017) The mission of the U.S. Fish and Wildlife Service is working with others to conserve, protect, and enhance fish, wildlife, plants, and their habitats for the continuing benefit of the American people. The mission of the National Wildlife Refuge System is to administer a national network of lands and waters for the conservation, management, and, where appropriate, restoration of the fish, wildlife, and plant resources and their habitats within the United States for the benefit of present and future generations. SUGGESTED CITATION: U.S. Fish and Wildlife Service. 2018. Preble’s Jumping Mouse Surveys on the Rocky Flats National Wildlife Refuge 2014-2017. U.S. Fish and Wildlife Service, Colorado Front Range National Wildlife Refuge Complex, Commerce City, Colo. 26p. COVER PHOTO: The Rock Creek drainage at the Rocky Flats NWR (Alison Michael/USFWS) Introduction: The Rocky Flats site is a 6,240-acre former nuclear defense facility that was operated by the U.S. Department of Energy (DOE). All weapons manufacturing was performed in a 600-acre area in the middle of the site known as the Industrial Area. In 1992, the mission of the Rocky Flats site changed from weapons production to environmental cleanup and closure. The DOE completed the cleanup in accordance with the Rocky Flats Cleanup Agreement (RFCA) under oversight by the U.S. Environmental Protection Agency (EPA) and the Colorado Department of Public Health and Environment (CDPHE). Under the Rocky Flats National Wildlife Refuge Act of 2001 (Refuge Act), portions of the 6,240-acre Rocky Flats Environmental Technology Site became the Rocky Flats National Wildlife Refuge (NWR). Refuge goals for wildlife and habitat management are to “Conserve, restore and sustain the biological diversity of the native flora and fauna of the mountain/prairie interface with “particular consideration given to threatened and endangered species”. A Comprehensive Conservation Plan (CCP) and Environmental Impact Statement (EIS) for Rocky Flat NWR was signed in 2004. The CCP describes the desired future conditions of the Refuge and provides long-range guidance and management direction over the 15-year duration of the plan. In 2012, the Rocky Flats NWR was expanded to the southeast when the U.S. Fish and Wildlife Service purchased 623 acres of former School Trust lands. Purpose/Need: Rocky Flats NWR had supported two wildlife species listed as threatened or endangered under the Endangered Species Act (ESA). The bald eagle in the lower 48 States was removed from the ESA list in 2007 (Federal Register 2007). The Preble’s meadow jumping mouse remains listed as threatened. The Preble’s Meadow Jumping Mouse (Zapus hudsonius preblei) (Preble’s) is a small rodent with an extremely long tail, large hind feet and long hind legs, all adapted for jumping (Federal Register 2009). The subspecies inhabits the foothills of southeastern Wyoming, and the eastern edge of the Front Range of Colorado in certain riparian areas and their adjacent uplands below 7600 feet in elevation (Federal Register 2003). The subspecies has been listed as a threatened species in Colorado since 1998 (Federal Register 1998) Preble’s occur in every major drainage on the Refuge. The mouse occurs in habitat adjacent to streams and waterways along the Front Range of Colorado and southeastern Wyoming. At the Refuge, Preble’s also has been found in wetlands and shrubland communities adjacent to the Rock Creek and Woman Creek drainages. Knowledge of the natural history and ecology of the Preble’s is limited. In addition to directing the listing of species as threatened or endangered, Section 4 of the ESA also directs the Secretary to “designate any habitat of such species which is considered to be critical habitat,” 16 U.S.C. § 1533(a)(3)(A)(i). Under the ESA, a species’ “critical habitat” includes areas occupied by the species that are “essential to the conservation of the species” and whose “physical or biological features may require special management considerations or protection.” Id. § 1532(5)(A)(i). It also includes areas not occupied by the species that are nonetheless essential to the species’ conservation. Id. § 532(5)(A)(ii). The Service has defined the “physical or biological features” required in critical habitat in terms of “primary constituent elements” (“PCEs”), defined for Preble’s as riparian corridors or adjacent floodplain and upland habitat (Federal Register 2010). The physical and biological features are the PCE “laid out in the appropriate quantity and spatial arrangement for conservation of the species.” (Federal Register 2009) The Service has designated critical habitat for Preble’s, some of which is located on the Refuge (Federal Register 2010). This included approximately 1,108 acres of critical habitat within the former Rocky Flats Site (which includes both the Refuge and DOE-retained lands), but does not include any lands purchased in 2012 (the so-called “Section 16” portions of the Refuge).1 Critical habitat on the Refuge equals the stream plus 120 m outward on each side (see map of Unit 6 – Rocky Flats, Federal Register 2010). To protect, maintain and improve Preble’s habitat, one of the refuge CCP’s strategies is to : survey Preble’s locations and habitat every 2-3 years for the presence or absence of the mice. This report shows small mammal trapping results from the three major drainages on Rocky Flats NWR from 2014-2017. No Preble’s mice were captured during this period. Previous Studies: During the cleanup investigation of the former Rocky Flats plant, captures of Preble’s between 1991 and 1993 were considered “incidental.” In 1991, seven individuals were captured as a part of a larger small mammal inventory of xeric, mesic, and reclaimed grassland and riparian habitats. This was the first record of a Preble’s at the former Rocky Flats site (Kettler et al. 1994). In 1992 and 1993, it was reported that there were 1.5 captures of Preble’s in 6,150 trap nights. In 1994, the trapping program was modified to include intensive live-trapping efforts in Woman, Walnut, and Rock Creek resulting in 23 different individual Preble’s captures and a recapture rate of 68% (23/34) (Kaiser-Hill Company LLC 1996). In 1995, eight individuals were configured with radio transmitters resulting in the location of one hibernaculum in Walnut Creeks. Population densities were also calculated at up to 36.3/ha. The authors determined that 1994 trapping efforts were biased, in that transects were largely ecotonal 1 In 2012, a total of 12 acres of designated critical habitat for the Preble’s mouse was removed as a part of the required land exchange for a transportation corridor located on the eastern boundary of the Refuge. Currently, there are currently 1,096 acres of federally designated critical habitat in the area. and were established in large measure along the edge of riparian shrub communities and along tributaries. In 1995, sampling patterns were adjusted to grids resulting in higher Preble’s capture rates. A total of 81 Preble’s were captured in 1995 over 17,347 trap-nights Preble’s captures were highest in high litter (>50% of ground cover); rock cover was relatively low (0-30%); all plots had measurable herbaceous foliar and ground cover; and the majority of capture site (68.9%) were located within 2.5 m of the edge of significant woodland canopy (usually riparian or tall shrubland). (Kaiser-Hill Company LLC 1996). Smart Ditch also supports suitable habitat with a continuous willow component along its banks. A single Preble's meadow jumping mouse was captured along Smart Ditch in 1993 (DOE 1994) and in 2001 (Kaiser-Hill Company LLC 2002). In 1996, further habitat characterization and macrosite analysis occurred (PTI Environmental Services). Trapping occurred in five locations in the Walnut, Woman, and Rock Creek drainages. Trapping resulted in one new Preble’s location at the confluence of the Antelope Springs tributary on Woman Creek. Habitat characterizations for Preble’s included: • Lower Rock Creek Drainage: Preble’s were captured on slopes ranging from 1 to 12°, with over 80 percent occurring on slopes of 0-10 degrees. Over 88 percent occurred on north-facing slopes with aspects between 270° and 90°. Captures were located at riparian (mostly level areas next to streams) and bottom-slope positions. All captures were within 15m of the stream and more than 77% occurred within 1-5 m of the stream and within 10 m of an embankment (mean = 4.3 m). The mean distance from a capture location to a continuous canopy edge was 1.2 m with 100% occurring within 0-5 m. The canopy species most often encountered was Coyote Willow (Salix exigua). • Walnut Creek Drainage: Preble’s were captured on slopes ranging from 1 to 40°, with over 50 percent occurring on slopes of 0-10 degrees. Over 92 percent occurred on north- facing slopes with aspects between 270° and 45°. Captures were located at riparian (mostly level areas next to streams), bottom-slope and middle-slope positions. 79% of captures were within 15m of the stream and more than 76% occurred within 1-5 m of the stream and within 15 m of an embankment (mean = 9.3 m). The mean distance from a capture location to a continuous canopy edge was 4.4 m with 100% occurring within 0-5 m. The canopy species most often encountered was Choke Cherry (Prunus virginiana). • All captures at all sites were made within 25 m of the stream and within 25 m of an embankment, indicating a strong association with the stream channels and the proximity of embankments for potential hibernacula.