The Endangered Species Act has just turned 30 years old, and for at least 20 of those years, its friends and foes have shared a common assumption about the reaction of some landowners when they discover an endangered animal on their land:
Shoot, shovel and shut up.
That pithy advice sprouts on billboards and bumper stickers across the country, wherever different sets of residents - wolves and cattle ranchers, for example, or rare songbirds and suburbanites - occupy the same real estate.
But does the slogan reflect reality? Are some landowners so anxious to escape government regulations that they'd rather bulldoze a colony of rare plants or bury a litter of wolf pups than obey the law?
Yes, according to University of Michigan researchers who studied how 379 residents of Colorado and Wyoming reacted to a rare rodent, the Preble's meadow jumping mouse, which is listed as a threatened species.
The mouse happens to inhabit the sort of land that people prize: tree-lined riverbanks in one of the West's fastest-growing regions, between Colorado Springs, Colo., and Cheyenne, Wyo.
One of the most controversial and far-reaching provisions of the Endangered Species Act makes it illegal to harm any endangered or threatened species' chances for survival - not just by killing individual animals or plants, but also by eliminating their food and shelter, even on private land. That means a landowner with a colony of threatened mice might face land restrictions that a mouse-free neighbor would not.
In the new study, made public last month, 22 percent of landowners said they would try to improve living conditions for the meadow mouse on their land. But 14 percent said they would deliberately mow the fields where the animals feed or chop down the riverside shrubs where they nest.
When the size of the landowners' holdings was figured in, the scales were almost perfectly balanced between the threatened creatures' friends and foes - owners of 25 percent of the land said they would manage the property to benefit the mouse, and owners of 26 percent said they would try to get rid of the animal.
"This is only one particular species, but it is cause for concern," said lead researcher Amara Brook. "It seems that the [law] is creating an incentive for some people to take actions that harm the species, rather than helping it."
The study is the first attempt to survey private landowners' actions in endangered species' habitat. More glamorous species might fare better, Brook said, and responses might vary in other parts of the country.
But the law has triggered hot disputes and high emotions nationwide, including Maryland's Eastern Shore, where the endangered Delmarva fox squirrel has forced some developers to set aside land for the squirrel.
Experts say the act is the nation's most polarizing environmental law because it is the most uncompromising.
"I refer to the Endangered Species Act as the pit bull of environmental laws," said Don Berry, executive vice president of the Wilderness Society. "It's got the most teeth."
Critics who claim the Endangered Species Act was never intended to protect every bug and weed - or that its drafters didn't mean to restrict private land use - just haven't read the law carefully, said Princeton University ecology professor David Wilcove.
Alarmed by findings that the planet is in the midst of the largest wave of extinctions in history, Congress vowed in plain language to protect every vanishing living thing, restore each to abundance and preserve the landscape on which they depend. The law ordered the Interior Department to identify essential areas, known as "critical habitat," that each listed species needs to survive and thrive.
"The recognition was that species were increasingly being lost to habitat loss, as opposed to over-harvesting, like the American alligator," said Berry, a former Interior Department official who, in the 1970s, helped write the policies and rules that carry out the law.
The legislation easily passed through Congress, and President Nixon signed it into law on Dec. 28, 1973. Congress has since reaffirmed the law, most recently in 1985.
The law has brought 15 plants and animals, including the American alligator and the peregrine falcon, back from the edge of extinction to healthy populations. Still, about 1,200 species are now listed as threatened and endangered. As the number of listed species grew, so did the conflicts between their needs and humans' aims for the land.
Today the law is more than a decade overdue for congressional review, but leaders refuse to bring it up for a vote, instead keeping it in force by approving its annual budget.
The Interior Department opposes the process of designating critical habitat on the grounds that it's expensive, adds no protection and actually invites vandalism and habitat destruction. But during the past two years it has earmarked about 38 million acres as critical habitat, mostly in response to environmental groups' lawsuits.