Denver Area Block Clearance for Preble’s Meadow Jumping Mouse
Mark R. Hunter, Chief, Maintenance Program

The Preble’s meadow jumping mouse (Zapus hudsonius preblei) (PMJM) is a subspecies of meadow mice found only in riparian pockets along the Front Range of the Rocky Mountains between southern Wyoming and Colorado Springs, Colorado. The 2 -ounce rodent is three inches long with a six-inch tail and long hind feet adapted for jumping.

On May 12, 1998 the U.S. Fish and Wildlife Service (USFWS) published a final regulation to list the PMJM as a "threatened" species under the federal Endangered Species Act (ESA). The "threatened" designation provides more flexibility then the "endangered" listing in meeting the goals and requirements of the ESA. Under this designation state and local governments and landowners can play a larger part in establishing rules for its recovery.

Even before the "threatened" listing the USFWS had established interim guidelines for trapping surveys to determine the presence or absence of the PMJM and to gain more information about the subspecies. With the decision to list the PMJM as "threatened" the trapping surveys and habitat assessments became mandatory for many construction projects below 7400 feet elevation that impact wetlands and/or streambanks. The link between these construction projects and the ESA is that such projects fall under the jurisdiction of Section 404 of the federal Clean Water Act. The Section 404 regulations require that all ESA precautions must be observed when applying for a 404 permit for a construction project.

Many PMJM surveys and habitat assessments have been done over the last several years. Since 1997 over 300 trapping surveys within the Denver area have failed to locate PMJM. Based on this information discussions were held with the USFWS regarding the possibility of a block clearance for the PMJM. A block clearance is a zone in which the USFWS has determined that the species in question in no longer likely to exist.

The USFWS encouraged UDFCD and its consultant, ERO Resources of Denver, Colorado, to compile all the trapping surveys and outline the area that showed consistent negative findings. The result was a map that included most of metropolitan Denver, but excluded the likely PMJM areas in Douglas, Jefferson, and Boulder counties. In addition to the USFWS, the proposed clearance map was reviewed by biologists from the Colorado Division of Wildlife, members of the Preble’s Meadow Jumping Mouse Technical Working Group, the Colorado Preble’s Meadow Jumping Mouse Science Advisory Team, and the Preble’s Meadow Jumping Mouse Recovery Team.

The USFWS has formally accepted the PMJM block clearance map submitted by UDFCD. The map, prepared by ERO Resources, describes that portion of metro Denver where ESA precautions for the PMJM are no longer necessary. The USFWS approval letter recognizing the map is dated July 17, 2000 and is valid for three years. The Tri-Lakes Corps of Engineers office in Littleton, Colorado will accept Section 404 permit submittals that appropriately use the block clearance map as a reference. Of course, if evidence of a PMJM is found in the future inside the clearance zone the map will be subject to modification.

The USFWS has a website for the PMJM. The address is "" They have posted a copy of the approval letter and a copy of the block clearance map on the website. Click on the map and it will be displayed using Acrobat Reader.

Feel free to refer to the clearance map when submitting for an Individual 404 permit or when verifying nationwide 404 coverage. If your project is within the clearance area you should indicate so in the 404 submittal letter to the Corps of Engineers and include a reduced copy of the map with an "X" marking the project location. For the submittal letter it is suggested you state something like the following:

"This project site is within the boundaries of the block clearance and is indicated with an X on the accompanying clearance area map. Based on the designation of the block clearance zone as recognized by the USFWS in their letter dated July 17, 2000 it is not necessary to conduct Preble’s meadow jumping mouse habitat assessments or trapping surveys for projects within the block clearance boundaries."

If the proposed project is not within the clearance zone the map is of no benefit for Section 404 permit submittals and the normal procedures of PMJM habitat assessments and trapping surveys are still in effect. Contact the Corps of Engineers (303-979-4120) or the United States Fish and Wildlife Service (303-275-2370) for more information on the Preble’s meadow jumping mouse.

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