Rare creatures of desert springs
By MEGAN WILDE / Script for Marfa Public Radio's Nature Notes
In three small spring-fed pools, surrounded by desert in Big Bend National Park, the Big Bend Gambusia hangs on to a fragile existence. During the last Ice Age, when Mastodons roamed West Texas, these tiny guppy-like fish adapted to a life of gobbling mosquito larvae in the Big Bend’s warm spring waters. Now their only home on Earth is a quarter-mile cluster of springs near Rio Grande Village. That’s the smallest geographic range of any known vertebrate. If those springs dry up, or if the consistently warm water temperatures began to change, it would mean imminent death and extinction for the Big Bend Gambusia.
This is not an unusual story in the Chihuahuan Desert. Wherever springs interrupt the otherwise arid desert floor, you’ll find that precious water sustains diverse flora and fauna. There’s also a good chance you’ll find plants or animals that occur nowhere else in the world except a few isolated wet spots in Far West Texas. What other desert inhabitants live in these watery West Texas Galapagos?
From the Chihuahuan Desert Research Institute in Fort Davis, Texas, this is Nature Notes. Hello, I’m Dallas Baxter.
There is a litany of springs amid the high desert’s dry flatlands and mountainous folds. Social Disease, Know Nothing, Wildhorse, Burro and Boot are among several hundred spring names dotting our region’s landscape, according to Gunnar Brune’s book Springs of Texas. Big Bend Ranch State Park claims about 130, and two of those feed the second and third highest waterfalls in Texas. Big Bend National Park hydrologist Jeff Bennett says about 300 water sources have been surveyed there. The Davis Mountains too drip with springs and seeps. Some of these gush year-round, others flow seasonally; some scarcely trickle from a rocky cliff, and others are now dry.
However water emerges from the desert’s hidden topography, a variety of plants and animals depend on it. Gently clapping leaves of pale-trunked cottonwoods and the showy sway of willows often divulge a spring’s location. These native trees, as well as exotic invasive salt cedars, are among Big Bend’s thirstier plant residents. Sul Ross greenhouse manager Patty Manning says clusters of sedges, Maidenhair ferns and the tall fluffy plumes of Deer Muhly grass are also commonly found at springs here. Less commonly found is Hinckley’s columbine, which keeps its feet wet at only one spot in southern Presidio County.
Water-loving plants create islands of shade and shelter for many animals in an otherwise inhospitable desert environment, says Raymond Skiles, a Big Bend National Park wildlife biologist. Besides hosting amphibians and aquatic invertebrates, spring habitats are essential for many of the region’s mammals – javelina, deer, foxes, bobcats, bats, raccoons, skunks and the myriad rodents at the base of the food chain. While these animals may not live at springs all the time, they never stray too far from these reliable water sources, Skiles says.
Migratory birds, like the Vermillion flycatcher and Black-capped vireo, also depend on these shaded, moist oases as safe places to stop and rejuvenate for the night. Without them, the birds’ long and stressful passage across the desert would be even more treacherous, if not impossible.
Humans too have settled around the region’s springs for millennia. But since we began tapping the groundwater with wells, many springs have stopped flowing. At historic Fort Davis for example, a stand of towering cottonwoods is the only testament to waters that no longer reach the surface. Or looking at the Balmorhea valley today, you wouldn’t know that it was once a vast marshland, threaded with rivulets and lush grasses.
The mighty spring network that watered that valley has been diminished over the last century, says John Karges, the Nature Conservancy’s regional program manager. With agricultural development and occasional drought, the groundwater has been pumped faster than rainfall can replenish it.
San Solomon is still the popular focal point of Balmorhea State Park and remains one of the five largest springs in Texas. But Phantom Spring, which emerges from a cave west of Balmorhea, no longer flows without assistance. A pump deep in the aquifer now squirts water out the cave’s mouth, providing life support to a unique group of creatures. Without that flowing water, a few rare types of snails and a rare crustacean would be wiped from the planet, and two species of endangered fish, the Comanche Springs pupfish and Pecos gambusia, would be closer to extinction.
These two tiny fish were once well represented in the Pecos River basin, but they were brought to the brink of extinction after a few springs around Fort Stockton went dry. Both Comanche Springs and Leon Springs failed on the heels of the 1950s drought and Clayton Williams Sr.’s landmark court case that established the right of capture.
When those springs disappeared, the Comanche Springs pupfish was thought to have disappeared with it. Fortunately another population was later found at Balmorhea State Park and at Phantom Spring.
The Pecos gambusia also lives on at these springs, as well as another desert spring, Diamond Y, a few miles north of Fort Stockton. Now protected as a Nature Conservancy preserve, Diamond Y is what Karges calls a West Texas Galapagos.
The preserve is surrounded by pump jacks and gas rigs, and the spring-fed pool it protects isn’t much to look at. But that desert puddle sustains a variety of very rare and imperiled creatures. A few types of snails, a crustacean and crayfish, and the Leon Springs pupfish live nowhere else on Earth. It’s also the only place the Pecos sunflower, or puzzle sunflower, can be found on the planet, and Karges says three even rarer plants live under the sunflower.
At Diamond Y preserve, as well as the state and national parks, the last footholds of Far West Texas’s most threatened spring-dependent plants and animals are protected, but their survival is not guaranteed. Continued groundwater pumping, drought, climate change and invasive species loom as threats to conservation efforts. And if any of our desert spring oases dry up, the tree of life is likely to be a little less full.
Nature Notes is produced by KRTS, Marfa Public Radio in cooperation with the Chihuahuan Desert Research Institute, in Fort Davis, TX.
This episode of Nature Notes was written by Megan Wilde, based on her article in the summer issue of the Desert Candle. I’m Dallas Baxter. Thanks for listening.