From the The San Diego Union-Tribune, Saturday May 7, 1994.
Tiny, rare rodent could cost project big bucks
Call it mighty mouse.
A tiny, furry brown creature that may be the world’s smallest rodent — the Pacific pocket mouse — could change the fate of a multimillion-dollar sewage-treatment plant to be built near the U.S.-Mexican border.
Since April 18, biologists from the U.S. Fish and Wildlife Service have been scouring the proposed sites of the waste-water plant and its collector and discharge pipes for signs of the mouse, an endangered species last noted in the Tijuana River region during the 1930s.
Wildlife officials want to make sure the mouse hasn’t been overlooked.
It would be easy to miss: Fully grown, the Pacific pocket mouse weighs about a fifth of an ounce — as much as two pennies. Not including the tail, it stretches to about 2 inches, and could fit on most people’s pinkie. Like other rodents, Pacific pocket mice are active at night. During winter months they hibernate underground.
PACIFIC POCKET MOUSE
Perognathus longimembris pacificus
“It’s just a little brown ball of fur,” said John Hanlon, a biologist with the Fish and Wildlife Service’s Carlsbad field office. “Even if we found only one, it would be a whole new ballgame.”
The Pacific pocket mouse was thought to be extinct until 1 1/2 years ago, when a few of the tiny rodents were discovered in south Orange County.
If found near the proposed site of the Tijuana River Valley plant, the mouse “could certainly delay the project,” said Charles Fischer, environmental protection specialist for the International Boundary and Water Commission, the binational agency responsible for building the facility. “But right now, as we stand, their study has not delayed anything.”
Located in South Bay, at Dairy Mart Road about 3 1/2 miles inland and 300 feet north of the border, the plant would treat sewage flowing across the border from antiquated and unconnected sewer lines in Tijuana.
Depending on where the mouse were found, its presence might require design changes or relocation of the plant.
The commission “would have to identify all their activities and we would respond by providing a biological opinion regarding the impact to the Pacific pocket mouse,” Hanlon said.
But as of yesterday, biologists had found no Pacific pocket mice — just common rats, Pacific kangaroo rats, house mice, deer mice and other rodents that found their way into the Wildlife Service’s nocturnal traps. The survey will continue through next week.
Not seen by scientists since 1971, the Pacific pocket mouse was believed extinct until 1 1/2 years ago, when a few were found scurrying around the headlands of Dana Point in Orange County. The known population remains small: Last year, scientists counted 39 there.
Between 1894 and 1932, scientists captured 134 Pacific pocket mice in the lower Tijuana River Valley, the southernmost of eight locations along California’s coast where scientists have documented the mouse since 1865, according to a study by biological consultant Richard Erickson. The northernmost location is Marina del Rey.