The inch-long, silver-colored desert pupfish has learned to embrace change. Once thriving in the ancient inland lakes and streams that filled Death Valley more than 250 million years ago, the pupfish got stranded in a few meager springs as bigger bodies of water dried up. But the fish didn’t just survive in their new—albeit more cramped—surroundings. They adapted.
“Because the pupfish were stranded in isolated areas, they evolved into different subspecies,” says park ranger Alan Van Valkenburg. “Now each type of pupfish has different adaptations. For example, the endangered Devils Hole pupfish lives in a warm spring in an underground cave on Death Valley’s east side. It can withstand very hot water temperatures, higher than 90°F.”
Though the desert pupfish is an endangered species, the stream by the boardwalk at Salt Creek is usually “squirming with fish” in spring, says ranger Alan Van Valkenburg.
Other localized subspecies are equally unique—and bizarre. The Salt Creek pupfish lives in an ultra-salty stream. While its ancestors used to swim in freshwater, this subspecies can now withstand saline water—an evolutionary adaptation similar to humans drinking gasoline instead of tap water.
Even though desert pupfish don't grow much bigger than a baby’s pinky finger and are endangered species, they are easy to spot during their spring mating season at Salt Creek, seven miles north of Furnace Creek. “For most of March and April, the stream by the boardwalk is squirming with fish,” notes Van Valkenburg. But once waters recede, the little fish leave, moving “far upstream to wait out the heat in deep source pools,” he adds.