ROCKY FLATS NATIONAL WILDLIFE REFUGE — The hunt is 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.