San Juan Capistrano may have its flocks of returning swallows, but Edwards Air Force Base in the Antelope Valley can boast of unlikely swarms of shrimp swimming in springtime desert pools.
In what scientists call a biological oddity, the heavy March rains have called to life masses of the tiny, dormant shrimp eggs. Many had been deposited long ago on the same clay lake beds where the space shuttles land--usually bone dry but amply flooded in recent months.
The shrimp appeared in large quantities for the first time in at least four years, base officials said, attributing their absence to the five-year drought. Scientists say the phenomenon probably has been occurring at Edwards and other western desert areas for millions of years.
For Mark Hagan, the base's civilian biologist, the unusual creatures, which can grow several inches long, are a reminder of the vagaries of nature.
"You don't expect a dry lake bed to have life in it. Then you put a little bit of water on it and it starts teeming with life," he said.
For officials at the base, in the Mojave Desert about 90 miles northeast of downtown Los Angeles, the shrimp are local legend--and even a bit of a hazard. The shrimp attract flocks of hungry birds, which can pose a safety hazard for the base's jets.
The shrimp have been around far longer than the 300,000-acre Air Force base, which got its start in the early 1940s. And during rainy "shrimp" seasons, pilots are commonly warned of the influx of birds and what the Air Force calls BASHs--Bird Air Strike Hazards.
At least four species of shrimp have been found at Edwards, including three types of so-called fairy shrimp, Hagan said. They tend to be the largest, with long, translucent bodies, spiny legs and the unusual habit of swimming upside-down. The base also has tadpole shrimp, a smaller, bottom-hugging variety.
The desert shrimp, freshwater cousins to the saltwater restaurant variety, have a life cycle ranging from less than two weeks to more than a month, scientists say. The eggs they lay during wet periods may lie dormant in dry soil for years until the next big rain brings them to life.
Scientists believe the desert shrimp, which appear to feed mostly on organic particles and algae in the water, evolved from the shrimp species that may have inhabited the Mojave Desert millions of years ago when it and the Antelope Valley were covered by the sea.
The shrimp do not pose any major problems at Edwards, where the threatened desert tortoise is more of a concern.
Some workers at Edwards recently were eagerly collecting water-filled jars of the shrimp to show off to their colleagues. But no one appeared to be rushing them home to barbecue. "I don't know if you can eat them or not," Hagan said. "But I'm not sure I'd want to."