No dice on finding mice
A search for the threatened species comes up empty.
ROCKY FLATS NATIONAL
The hunt is WILDLIFE REFUGE» on for the Preble’s meadow jumping mouse — as is a Trump-backed fight that holds it up as proof the Endangered Species Act needs tweaking.
The tiny mouse with a huge vertical leap — officially designated threatened, meaning vulnerable to extinction — has for two decades forced developers and cattlemen to take better care of streamside habitat along Colorado’s Front Range, one of the nation’s fastest-growing regions.
This particular hunt began late one recent night at Rocky Flats National Wildlife Refuge, in willows along Rock Creek — and the U.S. Fish and Wildlife Service survey crew quickly found that the springy, long-tailed Preble’s mice are lying low.
Surveyors running 200 traps a night all week saw nothing of the mouse’s famed leaps and midair twisting to evade predators. And this habitat is as good and undisturbed as it gets, because Rocky Flats was closed off as the site of a Cold War nuclear bomb factory.
In fact, the crew did not catch a single Preble’s mouse along a 1-mile stretch of the creek where, on average, 44 mice had appeared in previous surveys.
“Empty,” biologist Alison Michael said as she opened one baited metal trap after another while refuge manager Dave Lucas looked on.
It was one of several mouse-trapping expeditions planned this summer to detect the Preble’s mouse, including searches at the U.S. Air Force Academy north of Colorado Springs and in the foothills west of Boulder.
Failing to find any here last week does not prove scientifically that they’re gone. But it adds to federal government trapping data showing that even when shielded by federal law, Preble’s mice have declined — and are likely to further decline — across their habitat, which extends from Wyoming to Colorado Springs.
Saving the mouse requires continued work by all to preserve and protect streamside habitat, which also helps many other species and people who rely on streams for water and recreation, federal wildlife officials say.
Yet development pressures mount — to widen Interstate 25 through mouse habitat between Castle Rock and Colorado Springs, to build new housing and to install more big-box stores. And, in Washington, D.C., and in proindustry law offices, attorneys argued last week that it makes no sense to give so much power to a mouse.
The Colorado Association of Home Builders, Colorado Cattlemen’s Association, and Housing and Building Association of Colorado Springs recently petitioned the federal government demanding that the protection granted in 1998 for the Preble’s mouse be removed.
These groups contend saving streamside habitat hurts their business, and they argue that the mouse is not a separate-enough species, distinct from the more-abundant Western jumping mouse, to qualify for Endangered Spe-
cies Act protection.
“Why waste money protecting a population that is not important to the species as a whole or to biodiversity?” Pacific Legal Foundation attorney Damien Schiff said, making the groups’ case to delist the Preble’s mouse. “It is not economical or socially feasible to protect every population. You should prioritize based on the most ecologically or biologically significant species. The Preble’s jumping mouse is not high on that list.”
Last week, Congressional Republicans began trying to significantly change the Endangered Species Act — a cause President Donald Trump has encouraged by calling environmental rules “out of control” and delaying protection for the rusty patched bumblebee.
One bill would stall protection for endangered species if economic costs are deemed overly burdensome. Democrats oppose the changes, accusing Republicans of kowtowing to oil and gas and other industries in a way that would ruin the nation’s system for preventing extinctions.
The Preble’s mouse, found only on Colorado’s Front Range, “is a case in point,” Schiff said. “You have a significant amount of time and resources being expended over a population that doesn’t merit that degree of attention.”
Over 20 years, requirements to minimize harm to Preble’s mouse habitat have hurt landowners looking to develop, Colorado Association of Home Builders CEO Scott Smith said. “If you have property deemed to be mouse habitat, it has significant impacts. It sterilizes your property.”
“For the vast majority of people, when you have a true endangered species, you want to figure out how to work with U.S. Fish and Wildlife and make sure you aren’t doing irreparable harm,” Smith said. “There’s no problem with that. The problem is that there is an environment created for mischief. You can slow or hurt development by trying to identify an endangered species.”
Colorado Cattlemen’s Association vice president Terry Fankhauser said regulations on streamside construction have had a negative economic impact. He lauded work by Gov. John Hickenlooper and other Western governors to give states a greater voice in handling endangered species issues.
The Preble’s mouse stands out as a “relic species” that evolved during the ice age, when Colorado was wetter. The mouse adapted to wet conditions. Then, as glaciers retreated, the mouse was confined to increasingly isolated stream corridors. Preble’s mice need free-flowing water to drink, unlike other species in the semi-arid West that can metabolize water from plants or drops of dew.
They build apple-sized orbs out of grass — “day nests,” biologists call them — and can climb inside to endure intense heat.
They hibernate from October until May, burrowing as deep as 2 feet, recognizing a need to stay outside stream flood zones and below frost zones.
And Preble’s mice swim, using their tails, which are up to twice as long as their bodies, as rudders.
Not to mention jumping. They jump to evade predators from coyotes to owls, Fish and Wildlife Service biologist Craig Hansen said. “I’ve seen prodigious leaps, from a foot up to 5 feet. They crouch in vegetation and wait for predators to get close. It is a shockand-awe defense. It surprises predators. Then the mouse jumps away.”
The Endangered Species Act requires landowners to at least consult with federal officials before disturbing mouse habitat and to obtain permits for projects where harm can be minimized through careful planning. Over two decades, Hansen said, this process has resulted in higher-quality development along Colorado’s Front Range that saves streamside terrain.
“Now, in some of those riparian corridors, we have increased property values,” he said. “That might not be there otherwise.”
The Preble’s mouse counts can be slow. Trappers lay out metal boxes at night, baited with molassescovered oats or alfalfa. They put them in thick willows, then check them at dawn.
“I would hope to get four to six,” Michael said as she trudged through shortly after sunrise. Most traps were empty. Some contained deer mice, voles and woodrats. The Rocky Flats refuge, scheduled to open to the public next summer, also is home to elk, meadowlarks, coyotes, owls, bats, fireflies and, based on recent sightings, a cougar who may have cubs.
Preble’s mice “are part of the ecosystem here,” Michael said. “They have a role to play. They feed things people like to see. They’re a sign of wildness, of a healthy ecosystem.”
Not finding the mice is “disappointing,” and more surveys will be done, said Lucas, the refuge manager. While traps last week didn’t catch Preble’s mice, the survey also gave evidence of abundant other nocturnal creatures along Rock Creek. “They are indicators our riparian system is healthy.”
Previous mouse surveys found scores of the mice along Front Range streams, including an estimated 77 along Rock Creek in the late 1990s. But, increasingly, Preble’s mice aren’t found.
A Fish and Wildlife Service review in 2013 concluded that human development and other activities fragmented and changed Preble’s mouse habitat, that the mice are likely to face extinction “within the foreseeable future,” and that they require continued protection.
The most recent surveys done establish an overall decline, Hansen said.
“Development has proceeded along the Front Range,” he said. “In areas where development could affect the mouse, we have worked with developers and other project proponents to avoid and minimize their potential impacts on the mouse, other listed species, and other natural resources — and, if necessary, pursue incidental-take permits under the ESA so that projects proceed.”
It would take years before the mouse could vanish, because 34,935 acres of “critical habitat” along streams in Colorado ensure survival is likely. And wildlife researchers say it is difficult to prove a species has gone extinct. If that happened, the Endangered Species Act protections legally could be removed. Few species have been removed from the endangered list due to extinction.
“We could delist the mouse due to extinction,” Hansen said. “But we’re not going to let that happen to this mouse. We have enough tools, and conservation partners, to make sure that doesn’t happen.”
Biologist Alison Michael on Tuesday holds a deer mouse captured in a trap in willows along Rock Creek at Rocky Flats National Wildlife Refuge. Not a single Preble’s meadow jumping mouse was captured.
Scott Quigley writes down information, while Alison Michael holds a deer mouse.
Alison Michael, left, hunts for a mouse trap at Rocky Flats. Above, a deer mouse looks up from one of the traps. Photos by RJ Sangosti, The Denver Post