Two men pleaded guilty to killing a rare pupfish in Devil’s Hole, a geothermal pool in Death Valley National Park. They entered the protected area in 2016, fired at least ten rounds, left beer cans behind, and one swam in the pool. The incident caused damage that biologists said likely destroyed eggs and disrupted breeding on the only spawning shelf the species has.
This is not the first time the site has drawn attention. In June 1965, a search and rescue team lowered a weighted line into a water-filled cave in the Nevada desert, looking for two missing men. The line extended 932 feet into the darkness and never touched bottom. The men, 19-year-old Paul Giancontieri and 20-year-old David Rose, had entered the water with a third man, Bill Alter, who surfaced but lost sight of the other two. Their bodies were never found.
The cave was already unusual before the disappearance. The water temperature holds steady at 92 degrees Fahrenheit year-round. The pool is home to a species of fish that exists nowhere else on Earth. The Devil’s Hole pupfish, about one inch long, was officially listed as endangered in 1967 under the Endangered Species Preservation Act. That made it one of the first animals in U.S. history to receive federal protection, years before the bald eagle.
The fish’s entire habitat is a single submerged limestone shelf roughly 11 by 16 feet, small enough to fit inside a bedroom. Sunlight reaches that depth, allowing algae to grow, and the fish lay their eggs there. Population counts have swung sharply over the decades, from several hundred to as few as 35 individuals.
The species became the subject of a landmark legal case in the 1970s. In 1952, President Harry Truman designated Devil’s Hole a national monument. In 1968, a cattle ranching family began pumping groundwater from wells connected to the same aquifer that feeds the pool. Water levels dropped, threatening to expose the spawning shelf. The federal government sued, and in 1976 the Supreme Court ruled unanimously in Cappaert v. United States that when the government reserves land for a specific purpose, it also reserves the water needed to fulfill that purpose, even if the water is drawn from miles away.
Scientists have also learned that the cave holds a long environmental record. In 1992, U.S. Geological Survey researchers drilled a 36-centimeter core of calcite from the cave wall. Oxygen isotope measurements along the core produced what the team interpreted as a continuous temperature record stretching back nearly 500,000 years. The timeline did not always match established climate records, and debate over the accuracy of the dating continued for decades. A 2024 study suggested that uranium movement within the calcite may have distorted some ages by as much as 12,000 years.
The cave itself remains only partially explored. Divers reached about 315 feet in 1965. In 1991, a USGS team led by diver Sheck Exley reached roughly 436 feet before the passage bent out of sight. Exley died in 1994 while attempting a depth record in a Mexican cave system. Modern divers have mapped Devil’s Hole to about 450 feet, and federal agencies describe the cave only as deeper than 500 feet. No one has seen the bottom.
The water in the pool reacts to distant earthquakes. In March 2012, a magnitude 7.4 quake in Oaxaca, Mexico, about 1,000 miles away, caused the water to surge and slosh. Similar responses were documented after quakes in Japan, Indonesia, Chile, and Alaska. In September 2022, a magnitude 7.6 earthquake in Mexico produced waves about four feet high inside the pool. In December 2024, a magnitude 7 quake off northern California sent waves around two feet high through the cave. In July 2025, a magnitude 8.8 earthquake in Russia’s Kamchatka Peninsula, nearly 4,000 miles away, generated waves about ten inches high in Devil’s Hole about 21 minutes later. Biologists linked earthquake-driven waves to a drop in the pupfish population from 191 to 38 after the 2022 event.
The 2016 incident led to criminal charges. Three men were identified as Steven Schwendorf, Edgar Reyes, and Trenton Sargent. Sargent, a convicted felon, pleaded guilty in 2018 to violating the Endangered Species Act, damaging federal property, and illegally possessing a firearm. He was sentenced to a year and a day in prison. His two companions received probation. One pupfish was found dead after the incident.
Genetic research has added another layer to the species’ fragility. In 2022, biologists at the University of California, Berkeley sequenced the first complete genomes of the Devil’s Hole pupfish. They found that an average of 58 percent of the genomes were identical across individuals, a level of inbreeding comparable to isolated wolf populations in Michigan, mountain gorillas in central Africa, and wild tigers in India. The authors identified at least 15 genes that had disappeared entirely from the genome, including one that helps related fish species survive in low-oxygen water. A preserved sample from 1980 showed similar levels of inbreeding, indicating the species has experienced repeated population bottlenecks for centuries. Estimates place the isolation of the species on that shelf at between 1,000 and 20,000 years.
In 2013, the U.S. Fish and Wildlife Service opened the Ash Meadows Fish Conservation Facility, less than a mile from Devil’s Hole. The $4.5 million lab contains a 100,000-gallon tank designed to replicate the cave, including an artificial shelf matching the dimensions of the natural spawning area. Biologists collect fertilized eggs from Devil’s Hole about once a month and raise the young in captivity. The program has released captive-bred fish into the wild and has kept the species alive during low points, including a 2013 count of just 35 individuals. Captive populations now outnumber the wild population.
Two fenced openings, Devil’s Hole and Devil’s Hole 2, connect to a geothermal aquifer estimated to cover about 12,000 square kilometers. Researchers estimate groundwater travel time from the recharge area to the cave at roughly 880 years. That means water sitting in the pool today may have entered the ground before Columbus reached the Americas.
Twice a year, teams of biologists and trained volunteer divers conduct a formal census of the pupfish. Researchers have conducted these spring and fall counts since the early 1970s, making it one of the longest continuous wildlife surveys in the United States. Historical counts exceeded 400 fish in the 1960s and 1970s, fell to 35 in 2013, and have occasionally risen above 200 in recent years. Climate models developed by USGS and University of Nevada researchers suggest that prolonged drought and regional groundwater pumping could gradually alter recharge rates to the aquifer over coming decades. That slow-moving threat operates on a different timescale than earthquake-driven waves, but both affect a species that lives in a habitat measured in square feet.
What keeps the pupfish alive is the extensive institutional infrastructure built around it: the captive breeding facility, the semiannual counts, seismic sensors, and the reinforced fence installed after the 2016 break-in. The species remains a biological indicator for a hidden water system that connects Nevada to regional faults and aquifers under pressure from forces no one can fully control. The pool has never been fully explored, and its bottom has never been seen. The line lowered in 1965 did not find it. Neither have any of the divers who followed. The fish does not inhabit the deep parts of the cave, and no one knows exactly how far down the passage continues. The cave does not need a threat to be dangerous. It just needs darkness, unstable rock, and a maze of narrow passages that punish mistakes permanently.
