Category Archives: Chihuahuan Desert

Images and writings about the flora, fauna, and natural history of the Chihuahuan Desert region.

Prehistoric Trackways National Monument

Tiny tracks from 280 million years ago are preserved in red siltstone.

Tracks in the Rocks

Mountains are nature’s mystery novel. Captured in layers of rock are stories about time, about life, about death. As I pass the Robledo Mountains just northwest of Las Cruces, New Mexico, I ignore the dry, sparsely vegetated cover, knowing an extraordinary story awaits me within the rock of the Prehistoric Trackways National Monument.

The monument, managed by the Bureau of Land Management, is relatively new, so infrastructure consists of a few interpretive panels, two dirt parking lots, and a hiking trail that switches up the hillside. I called ahead and signed up for a guided tour—the best way to discover the secrets of the Robledos.

Colin Dunn, paleontologist with the Bureau of Land Management, shows us a rock loaded with fossils.Skip the Dinosaurs

On that bright, spring, Saturday morning, a small group of hikers gather around Colin Dunn, the BLM paleontologist. We’ve come to see the fossilized trackways of creatures that squelched through mud 280 million years ago. “We’re skipping the dinosaurs,” Colin says. “Mammals, flowers, birds. Just skip it.” These tracks were made by animals 60 million years before any flower bloomed or dinosaur roamed the earth.

The trackway eroding from the Robledo Mountains dates to the Early Permian. At that time, New Mexico was part of a single, massive continent known as Pangea. The rocks that surround us are sediments from a shallow, warm sea that lapped against a tropical shoreline.

Fragments of sea urchin spines and shells make a jumble of shell hash in a rock.Shell Hash

We hike up a dry creek bed. Colin stops to show us long, thin sea urchin spines, round disks of crinoids (sea lilies), flat colonies of bryozoan, and ridged shells of clam-like brachiopods. These fossils create a layer of “shell hash”—a jumbled assortment of life in the Permian sea.

Tracks of a Dimetrodon are deeply impressed into red siltstone.


As we move inland from sea to shoreline, thick beds of red rock jut from the hillside. Colin scrambles to the first terrace. Crouched before a large, flat slab of siltstone he points out a series of tracks. About the size of my hand, the “palm” of each print is round and deeply impressed. The toes are long, thin, and sharply pointed.

“These are Dimetrodon tracks,” Colin tells us. Dimetrodon was the terrestrial terror of the Permian world. Lizard-like, with a bony sail fin down its back, the largest Dimetrodon was 13 ft. long and weighed 500 lbs. “This one was pretty small,” says Colin. “It was only about 100 lbs.”

Colin pulls a small rock out of his pocket. Clusters of three lines, each arranged like an arrow, cover the surface. “I was at White Sands and saw beetles making tracks just like this. I was totally geeking out!”

Walchia fronds from an upland forest washed downstream and pressed into the mud.Walchia Fronds

I am too. Fossilized bones fascinate me, but these tracks? Even better. Bones write the story of death. These footprints tell the story of life. I can picture an araeoscelid (go ahead and think lizard) scampering for cover, a beetle making its way across the mud, and the corkscrew twist of a worm as it drills a burrow. Raindrops dimple one rock; a mat of Walchia tree fronds from an inland forest is impressed on another. The fronds look like the potted Norfolk Pines I used to buy at the home improvement store.

By studying these tracks, paleontologists are unveiling twists to the mystery of Permian life. Initially, scientists believed Dimetrodon was a low-slung, lumbering thug. But the tracks—set close together and lacking belly scrapes or tail drag marks—suggest Dimetrodon was a sprinter rather than a plodder.

Colin tells me of petrified log jams and other track sites at the monument. He won’t share where they are though. “Have you heard of Fossil Cycad National Monument?” he asks. I shake my head, no.

“That’s the problem. Fossil Cycad had one of the world’s greatest concentrations of cycads. Then people came in and took them all. They shut down the monument because there wasn’t anything left to see. I don’t want that to happen here.”

I don’t either.

A sign at the monument tells of the trackway discovery and warns people not to collect rocks.

Getting There:

The Prehistoric Trackways National Monument is open to the public, but the best way to visit is with a knowledgeable guide. Tours to the Discovery Site are given once a month on Saturdays. Contact the Bureau of Land Management for more information.

To Learn More

Traces of a Permian Seacoast is a wonderful, beautifully illustrated book about the fossil trackways of Prehistoric Trackways National Monument. Purchase it from the link below to help support this blog!


Also posted in Fossils, Geology, New Mexico, Travel

Ghosts of the Past: Stromatolites

The 1.25 billion year old Castner Formation is exposed in the Franklin Mountains near El Paso.

I believe in ghosts. They hide in plain sight, urging us to listen to the stories they have to tell.

It was my birthday and, feeling just a wee bit sorry for myself (I’m of that age), I decided to go in search of something older than I was—the stromatolites of the Castner Marble in the Franklin Mountains near El Paso. Now, these stromatolites aren’t just a little older than I am, they’re way older than I am. About 1.25 billion years older. Yes, that’s right: 1.25 billion.

Math isn’t the strongest of my academic skills, but let’s work our way through this. Let’s say you wanted to count to 1.25 billion—just to get a sense of how colossal that number is. If you keep up a steady rhythm of a number per second (and absolutely no stopping for dinner, a potty break, or Facebook), it will take you 40 years to reach 1.25 billion. If you wanted to restrict your counting to a mere 8 hour day, buckle down for 120 years. Hopefully, you don’t get confused, skip a number, and have to start all over. That would be depressing.

Tiny, single-celled cyanobacteria create layered sedimentary rocks.

So I’m in search of 1.25 billion-year-old stromatolites. In case you’re wondering, stromatolites are a type of sedimentary rock created by single-celled photosynthetic cyanobacteria (that’s blue-green algae). These microorganisms like to congregate in large groups, forming sticky mats in shallow water along a shoreline. I don’t think anyone knows why the stickiness is necessary, but the result is that the bacterial mats accumulate sediment that clogs the system up. The bacteria, being photosynthetic, need the sun’s energy to produce food, so they move upwards, forming another mat on top of the sediment. And so it goes. Layer after layer, eventually forming a cauliflower-shaped lump of rock in shallow water.

Now the amazing thing is that these single-celled cyanobacteria have been carrying on like this for over 3.2 billion years. In fact, stromatolites are some of the oldest fossils in the world. They reached their peak diversity just about the time the Castner Marble stromatolites formed. After that, they’re harder to find. The theory is that grazers evolved that found a stromatolite mat downright tasty and pretty much ate them to near-extinction.

Arizona Barrel Cactus (Ferrocactus wislizeni) have hook-shaped spines that can grab an unsuspecting ankle.

I cajole a geologist friend into going with me, and we head westward, driving past yucca-studded grasslands and mesquite-topped sand dunes. We skirt El Paso and climb the Trans-Mountain Highway through the Franklin Mountains. I navigate, reading directions from the Geological Excursions to a Transmountain Precambrian Adventure field guide that I’d downloaded from the internet. We’re looking for Stop 2—the Castner Marble Stromatolites. A gust of wind shakes our vehicle as we round the corner.

We pull over onto a wide gravel patch (obviously not the first geologists to investigate this location) and begin walking back down the highway to the end of the guardrail. Another gust of wind nearly knocks me off the mountain.

The authors of the field guide suggest that we follow a small trail down into the valley, and up the other side. The stromatolites will be there.

The trail is, indeed, narrow, and very steep. I cautiously make my way down, trying to avoid the baseball-sized round rocks that ensure a quick—and most likely painful—descent down the slope. I skirt the lechuguilla, prickly pear cactus, and a barrel cactus or two to arrive at a 2 to 3 ft thick band of light-colored rock.

A layered band of stromatolites are exposed in the hillside.

“Are you sure these are stromatolites?” I ask Blaine. He’d gotten there before I had and was poking and prodding at the rock as geologists tend to do.

“Yeah, sure. Look.” He points to the thin, wavy layers in the rock. And there, right before me is evidence of the earliest life in the Chihuahuan Desert.

With just my naked eye I can distinguish layer after layer of sediments trapped by cyanobacteria over a billion years ago. To see the actual fossils, I’d need something slightly stronger, like a microscope. Most of the layers are flat-lying to slightly wavy—an indication that the mats collected sediments in relatively calm waters.

Stromatolites aren’t flashy like a trilobite fossil or spectacular like an ammonite. But all in all, they’re probably far more important. Stromatolites hint at the origin of life. When the cyanobacteria were trapping these sediments, the skies were pink—filled with methane and ammonia and other gasses that would kill us today. The land was barren. Not a single, living thing existed out of the water. But in the water, slimy mats of green bacteria clung together, creating their own little rock. The cyanobacteria were photosynthetic, and that nifty trick of converting the sun’s energy and some carbon dioxide into food while releasing oxygen as a byproduct was changing the world. A few billion years of lilliputian, single-celled bacteria releasing minute bubbles of oxygen created an oxygen-rich atmosphere necessary for complex life to evolve. Take a deep breath. That’s you I’m talking about.

Living stromatolites are pretty rare now, but they’re still around. In Cuatro Ciénegas, a desert wetland in the Chihuahuan Desert of northeastern Mexico, stromatolites can be found in the pozas or spring-fed pools of the marsh.

Scientists working at Cuatro Ciénegas cored one of the active stromatolites. The mat consisted of a complex community of microorganisms—not just cyanobacteria. The top layer was composed of diatoms (distinctive algae with transparent cell walls), below that was photosynthetic cyanobacteria. A third layer consisted of purple sulfur bacteria. These bacteria photosynthesize using hydrogen sulfide rather than water and produce elemental sulfur as their byproduct. Below that was a sulfur-reducing bacteria that takes the elemental sulfur and reduces it to hydrogen sulfide. “Each layer obtains and processes energy in a different way and produces different waste products, and yet it is an interactive community where each layer contributes to the survival of the mat as a whole,” the scientists concluded. Stromatolites are all about being good neighbors.

Stromatolite band exposed in the Franklin Mountains near El Paso.

I poke around the rocks, distracted by rainbow cactus with fat buds, and a lizard warming itself in the sun. None of this would be possible without those little cyanobacteria that lived in an ancient sea long, long ago. I wave at Blaine, who’s wandered off to look at a contact or something geological and we head back to the car. Finding rocks that are billions of years older than I am, makes me happy—all in all, a pretty spectacular birthday.

Also posted in Fossils, Geology, Texas

Places: West Texas Rest Stops

"Watch for Snakes" Warning Sign at a rest stop in west Texas

Watch for Snakes!

I’ve always thought of roadside rest stops as a necessity. You’re in, you’re out, you’re on your way. But I’m working on a photography project about the history of automobile tourism in West Texas, and I’ve started looking at rest stops in a slightly different way.

I grabbed my camera at this rest stop on I-10 between Balmorhea and Fort Stockton when I saw the “WATCH FOR SNAKES” sign. I’ve noticed warnings like this before, but they’re usually on a path leading to the picnic tables. This prominent sign made me think. Should I watch for snakes in the restroom? Given the fact that the rest stop is in the Chihuahuan Desert of West Texas, and that the restrooms have cool, tile floors, it wouldn’t surprise me at all if I found a rattlesnake curled up next to the toilet.

So I was on the lookout for snakes.


Buffalo Soldier with his horse

Buffalo Soldier Tile Mural

But I found something even more wonderful. Across the bathroom wall was this tile mural of a 19th century Buffalo Soldier and his horse. The Buffalo Soldiers were African-American infantry and cavalry troops stationed at Fort Stockton (1867-1886) and Fort Davis (1867-1885) after the Civil War. The soldiers were responsible for protecting travelers on the San Antonio-El Paso road, constructing telegraph lines, guarding watering holes, and conducting campaigns against raiding Apache and Comanche warriors.

This mural made me think. Were all of these mid-1960s rest stops decorated with murals depicting local history? I grabbed my map, checked for the next rest stop, and headed east.


A theropod dinosaur stomps across the landscape

Acrocanthosaurus Stomps Across a Cretaceous Swamp in Pecos County

The next stop was just past SH 190 (the Iraan turnoff).

Here, a salmon-pink dinosaur stomps across the wall, glittering white teeth bared. This one puzzled me at first. A dinosaur? Out here? But then I remembered a roadside park near Girvin (a few miles northwest of the rest stop) where, 120 million years ago, a theropod dinosaur squelched through the mud.  In 1965, highway workers uncovered its three-toed tracks preserved in the limestone of a creek-bed. Paleontologists decided that an Acrocanthosaurus—a genus of dinosaurs that existed in the early Cretaceous (125 mya to 110 mya) and had a distinctive short ridge along its spine—left the tracks as it foraged along the shore of an ancient sea.

Eureka! I was on to something. Like a bloodhound hot on the trail, I started looking for rest stops. The 1960s-era rest stops were not only examples of quirky, fun public art, but also related to the history of the region. I love this kind of thing.

Brands and an oil rig are depicted in the Nolan County rest stop.

Brands and Oil in Nolan County off Interstate 20

Over the next couple of days, I went on a rest-stop treasure hunt. Even my mom got involved. I’d promised her a Grand Adventure for Mother’s Day and suggested we drive the backroads of Central Texas looking at wildflowers. Instead, she remembered an old rest stop up near Fort Worth. Could we go check it out? You’ve just got to adore mothers like that. The old rest stop near Fort Worth was gone, but we discovered some other treasures.

The Nolan County rest stop (on I-20 between Sweetwater and Trent) was the most complex one that I visited on my three-day trip. Tile-work murals cover the entire bathroom. A frieze of historic brands circle the walls and against the back wall is an oil rig, quail, deer, and a variety of other wildlife.


Standoff between a cowboy and his Hereford.

Cowboy and Herefords, Nolan County

On the side wall of the Nolan County rest area the mural continues, depicting a cowboy with his Herefords. As with the other murals, there’s a story to tell. Nolan County was founded in 1876 and by 1880, there were 52 ranches in the area. Herefords, a British breed that was exceptionally suited to the Texas environment, gradually replaced Longhorns as the cattle of choice on the ranches. I wondered if the brands shown on the walls were those of the first 52 ranches, so I gave Melonnie Hicks, the Executive Director of the Pioneer City-County Museum in Sweetwater, a call. I caught her at a bad time, and she wasn’t sure about the brands. But, she told me, the museum has actual brands from those historic ranches, and anyone that’s curious can drop by the museum and take a look.

The oil rig is a nod to the discovery of oil in Nolan County in 1939 and an oil and gas industry that boomed in the 1950s.


Exhibits in rest stop on Interstate 20

The History of Auto Tourism Exhibit in Eastland County

I have to admit that I have a fondness for the old-style rest stops and their art, but I can see why the Texas Department of Transportation is replacing some of them with new, mega-safety rest areas. The old ones are small. Some are dark. People complain that there aren’t doors on them, making them potentially unsafe.

In 2001, TxDot began building a different style of rest stop. These are big, open, airy buildings with lots of parking, playgrounds, and even WIFI. But they’re more than that. To reduce the number of fatigue-caused accidents, TXDot engineers wanted people to stay longer. They worked with county historical commissions, schools, and other local groups to create rest areas that portrayed the local community. In a sense, they’re small museums, complete with interpretive panels, artifacts, and hands-on, computer-based interactive exhibits. They’re a destination on their own.

So next time you’re out for a long drive, pull off and enjoy the art and history of Texas rest stops. Which are your favorites?

Also posted in Places, Texas, Travel Tagged , , , , , , |

Places: Big Bend Ranch State Park’s Arroyo Mexicano

Big Bend Ranch State Park covers 311,000 acres of the Chihuahuan Desert.

Big Bend Ranch State Park: The Other Side of Nowhere

Big Bend Ranch State Park hugs the Mexican border and sprawls over 311,000 acres of the Chihuahuan Desert in West Texas. State park staff affectionately call it “The Other Side of Nowhere.” To the casual visitor, the park appears to be all rugged mountains, deep canyons, and miles and miles of rough roads designed to destroy your vehicle and shake the fillings loose from your teeth.

But those rugged mountains and deep canyons hold treasures if you’re a naturalist. The rough roads? They’re just a necessary evil if you want to experience the park.

Groves of cottonwood and ash trees line the bottom of Charro Canyon.

Cottonwood, Ash, and Oak Trees Line the Bottom of Chorro Canyon

I spend two days with Blaine Hall and Roy Morey exploring sites for a Native Plant Society of Texas field trip. Blaine aka “Big Foot” wears one shoe 3 sizes larger than normal to accommodate the brace and bandages that stabilize an ankle broken during a hike two weeks ago. Recently retired from his position as the interpretive ranger for Big Bend Ranch State Park, Blaine chatters away, teasing Roy and me, and pointing out geologic features as he skillfully guides the truck up rock-covered slopes, across ridges of limestone, and down sandy washes. He pulls over frequently so that we can enjoy the view.

Roy is quiet, not letting Blaine’s teasing phase him. Roy is a plant person. After retirement, he moved to Terlingua and began compiling photographs of the plants of Big Bend National Park. His hobby became a full-time pursuit, ultimately resulting in Little Big Bend: Common, Uncommon, and Rare Plants of Big Bend National Park. Once he completed that book, Roy shifted west and began working on a companion volume that will describe the plants of Big Bend Ranch State Park.

“I need to get up there someday,” says Roy, looking up at the sheer cliffs of a mountain. I’m surprised. Between Roy and Blaine, I would have sworn that they’ve walked every inch of the park’s 311,000 acres.

Today, we’re looking for unusual plants, so we head for Arroyo Mexicano, a box canyon that ends at Mexicano Falls. Canyons often harbor botanical treasures such as groves of cottonwood and ash trees and tiny plants that cling to the rock walls. Canyon walls protect plants from the harsh sun and fierce winds of the desert and often have seeps and springs that provide extra moisture. “One of the only mountain laurels in the park is up Arroyo Mexicano,” says Roy. “I hope it’s still alive.” It was.

An ammonite impression in limestone.

A Dinner-Plate Sized Ammonite Fossil in the Limestone

“Want to see an ammonite?” Blaine asks as we drive down Fresno Canyon. The creek has eroded deeply into the rock, exposing the flat-lying, flaggy Cretaceous limestone of the Boquillas Formation and the nobby, white limestone of the Buda Formation.

We pile out of the truck to admire the dinner plate-sized ammonite lying exposed on an upturned piece of Boquillas limestone. The thick limestones and this ammonite fossil are evidence of a time when a shallow sea covered part of Texas. You won’t see ammonites swimming around today. The last of them went extinct when a giant meteorite struck the earth about 66 million years ago. The short and long-term effects of the meteorite impact—wildfires, tsunamis, and clouds of debris that blackened the skies and blocked the sun for years—killed about ¾ of Earth’s plants and animals.

A Mexican Buckeye Provides Nectar for Pollinators

Mexican Buckeye Tree on the Edge of the Arroyo

We eventually arrive at the mouth of Arroyo Mexicano, shoulder our packs, and trudge our way up the canyon. I’d like to say that we hiked briskly, but I have to admit that I’m a trudger in soft sand. Fairly quickly, we see pools of water and a shallow stream meandering its way across the sand bottom. Groves of cottonwoods, their new leaves a beautiful, fresh spring green, provide shade along the way.

Occasionally a spot of pink reveals the location of a Mexican buckeye tree. These early-blooming shrubby trees are an important source of nectar for bees and butterflies. A Mournful Duskywing flits between flowers, ignored by a nectaring Grey Hairstreak. I search unsuccessfully for a Henry’s Elfin—a small brown and silver butterfly that uses Mexican buckeyes as a host plant. Henry’s Elfins are more common in the eastern United States, so seeing one in West Texas is pretty special. Roy and Blaine have moved on, so I quit looking for butterflies and hurry to catch up.

Huge velvet ash trees with their gnarly roots exposed.

Velvet Ash Trees in the Arroyo

As we move up the canyon, we walk under large velvet ash (Fraxinus velutina) trees. I am fascinated by the texture of the bark and the thick, gnarly roots wrapped around giant boulders. Of course, the exposed roots are also a warning sign. This canyon carries water—often with enough force to roll boulders and wash away enough sediment to expose the roots of trees. I check out the sky (gray clouds gathering) and look for high ground. The vertical walls of the canyon look back. I’m doomed.

Conglomerate boulder made of smaller, rounded, igneous rocks.

Volkswagen-sized Conglomerate Boulder in the Arroyo

In places, we skirt boulders the size of Volkswagon Beetles or larger. I envy Blaine his ability to read these rocks. “See,” he says, “this rock is made up of older rocks that have been cemented together to form a conglomerate.” This particular conglomerate is just a baby rock if you can wrap your mind around geologic time.

All of the “clasts” or smaller rocks that make up the conglomerate are volcanic in origin which means they were deposited about 27 million years ago. Over time, they broke away from their parent rock, were tumbled and smoothed, and came to rest in one place long enough for the white matrix rock to cement them all together again. The conglomerate eventually broke up, and Volkswagon-sized boulders tumbled down the slope, coming to rest in the stream bed.

Fern-covered walls and plunge pool of Mexicano Falls

Mexicano Falls at the End of the Arroyo

After about 3.5 hours of walking and stopping to admire rocks, plants, and scenic views we reach the end of the canyon. At this time of year, Mexicano Falls is more of a drip than a fall. Maidenhair ferns, yellow-flowered columbines, and thick carpets of moss fill the cracks where water seeps from the rocks. The plunge pool is thick with green algae.

Blaine points to a gap in the canyon rim where water funnels through to create a waterfall during the summer rainy season. I’d love to be there to see the waterfall, but then I remember those exposed roots and the flood debris wrapped three to four feet high up the trunks of the trees that we were walking through earlier. Flash floods are real and dangerous in this canyon.

The tiny, yellow, fringed monkeyflower hangs from the wet walls of the canyon.

Fringed Monkeyflower Hangs from the Wet Walls of the Canyon

While Blaine and I photograph the ferns and columbines, Roy walks the face, scouring the seeps for fringed monkeyflower (Mimulus dentilobus). “Found it!” he calls. Fringed monkeyflower is a rare plant in Texas, found only in places where water drips from the West Texas mountains. I’m surprised by how tiny it is. The bright yellow flower with its fringed petals and red spots in its throat rises above a mat of small leaves hugging the wet rock face. We’re lucky to find these in bloom. It’s only March and according to the field guides, fringed monkeyflower blooms from June to August.

Blaine and Roy fix a flat tire.

Flat Tire

The wind begins to blow, and the clouds build, getting thicker and grayer. We decide to return to the truck before a storm drenches us. The hike back takes about 2.5 hours. We quickly pack up and drive off, but Blaine stops almost immediately. He walks around the truck and discovers a flat tire. “That’s two this week,” he mutters. Razor-sharp rocks can slice through the sidewalls of a tire and mesquite thorns pierce treads easily. We unload all the gear to access the spare, and Blaine and Roy begin the laborious task of changing the tire. Fortunately, nothing goes wrong and within 30 minutes we’re back on the road. We eliminate a couple of side trips and head straight back to the park headquarters at Sauceda. Driving any further than necessary without a spare is foolish.

The flatirons of the Solitario provide a perfect backdrop for a patch of Big Bend Bluebonnets.

Big Bend Bluebonnets and the Solitario

Since Blaine and Roy have the flat-tire situation in control (and they’re a bit annoyed with my photographic documentation of the event), I wander off a few feet to photograph a patch of Big Bend bluebonnets with the flatirons of the Solitario in the background. The Solitario is a massive igneous dome created when molten rock pushed up the flat-lying rocks above it creating a circular feature 10 miles in diameter. The dome attracts geologists, botanists, and naturalists from around the world and is probably the most famous feature in Big Bend Ranch State Park.

I love going to the Solitario, but this opportunity to explore Arroyo Mexicano with Blaine and Roy was as close to perfect as a day could be.

Also posted in Geology, Plants, Texas Tagged , , , |

Places: Bitter Lake National Wildlife Refuge

Sandhill Cranes and geese head south

Sunrise at Bitter Lake National Wildlife Refuge, Roswell, New Mexico

The alarm goes off at 5 a.m. It’s cold, but I resist the urge to roll over and go back to sleep. I want to photograph Sandhill Cranes today, and they fly at dawn. I load up my camera gear and head for the Bitter Lake National Wildlife Refuge about 10 miles northeast of Roswell, New Mexico.

It’s a chilly 23F as I arrive, but the birds aren’t sleeping in either. As the sky brightens, they stir, murmuring and honking softly to each other. There are hundreds of Sandhill Cranes and thousands of Snow and Ross’s Geese in the shallow ponds of the refuge. Northern Shovelers, elegant Northern Pintails, and Mallard ducks disappear into the reeds as I stop to watch the sun come up.

The Sandhill Cranes and the geese take off, groups of birds bursting into flight all at once. They rise quickly into the air, to form V-shaped skeins as they head south.


Joseph R. Skeen Visitor Center overlooks wetlands

History of the Bitter Lake NWR

The Bitter Lake National Wildlife Refuge consists of 24,609 acres of wetlands along the Pecos River. Sinkholes, playa and oxbow lakes, freshwater springs, marshes, and man-made impoundments create a variety of aquatic habitats. Water in the desert is precious and tends to concentrate a broad range of species. Here, the wetlands support over 350 species of birds, 28 types of fish, and 110 dragonfly and damselfly species.

The refuge was established in 1937, three years after the passing of the Migratory Bird Conservation Act. The Act gave the federal government authority to purchase land for wildlife refuges. Although the refuge system was designed to protect upland game, mammals, and song, insectivorous, and ornamental birds; in the early years, waterfowl was clearly the focus.

By 1937, the region had suffered through 3 years of severe drought. Crops didn’t grow. The soil, no longer held in place by prairie grasses and forbs, blew away in billowing clouds. The once productive farmlands of the plains became known as the Dust Bowl. Waterfowl were hit hard by the drought, although overharvest by unregulated hunting and the draining of the wetlands to create farmland also took their toll. Early conservationists “Ding” Darling, Thomas Beck, and Aldo Leopold declared that waterfowl were in a state of crisis and called for an aggressive plan to create federal wildlife refuges.

Bitter Lake was chosen as one of the first wildlife refuges because of its location along the Central Flyway. The flyway—a great migratory route that cuts a swath across the middle of North America—is home to most of North America’s ducks and geese. Tens of thousands of birds move along the Flyway each year, flying north to breed in the summer and south for the winter.

Today, the refuge is known as much for its incredible diversity of dragonflies and damselflies as it is for its birds. The refuge also protects rare species including tiny snails the size of a glass seed bead, that cling to decaying leaves in the ponds. Shrimp-like amphipods—about the size of a lima bean—scoot across the bottom of sinkholes, and small fish dart for cover when a shadow crosses the pond surface. Many of these creatures can be found nowhere else in the world.


Exhibits explain this unique oasis in the desert.

The Joseph R. Skeen Visitor Center and Refuge Trails

Start your visit at the Joseph R. Skeen Visitor Center. There’s a 15-minute orientation film about the natural history of the refuge, beautiful interpretive exhibits, and even a tank of rare fish.

The back porch overlooks a large pond. With a pair of binoculars, you could sit out there all day and watch the American Coots and ducks going about their business. But to get the most from the refuge, jump back into your car and drive the Auto Tour or go for a hike.

Bitter Lake and the northern part of the refuge are closed to visitors, but the 6.5 mile Auto Tour loops around the ponds at the southern end of the refuge. The well-maintained dirt road is easily accessible by car. Along the loop,  several pull-offs guide you to overlooks where you can set up a scope and get a good look at the bird activity.

If you’d like to hike, five short hiking trails branch off from the Auto Tour road.  The trails lead into the uplands, around an oxbow lake, or out to observation blinds. They range in length from about 2 miles for the Oxbow Loop Trail to a short 0.2-mile butterfly trail.


Hundreds of Sandhill Cranes gather in the shallow ponds for the night.

Sandhill Cranes Gather For the Night

There’s something special at the refuge every season, but I was there in winter and specifically looking for the Sandhill Cranes and waterfowl that overwinter in this part of the Chihuahuan Desert. The Sandhill Cranes and light geese (a mix of Snow and Ross’s geese) leave the refuge at dawn to spend the day in nearby farm fields. At dusk, they return to the refuge to roost for the night in the shallow pond water where they’re protected from predators.

After my morning visit, I return to Bitter Lake NWR about dusk. I immediately hear the bugles of hundreds of Sandhills gathered on the far side of the pond. I was disappointed, afraid that I had missed the fly-in. But as I took photographs, I heard another flock coming in from the west. They flew straight overhead, dropping in altitude to land—kicking their feet outward to make space. Over the next few minutes, more and more birds arrived, adding to the controlled mayhem of the evening roost.

I was surprised that I was the only photographer there that day. I’ve been to see the Sandhill Cranes at the Bosque del Apache National Wildlife Refuge several times. Nearly due west and over the Capitan Mountains, the Bosque del Apache NWR is located on the Rio Grande and is a mecca for wildlife photographers. You stand tripod to tripod, vying for that “pristine nature” shot. But here, at the Bitter Lake NWR, I’m alone.

What I didn’t realize was that I saw something quite extraordinary. There are two subspecies of Sandhill Cranes that overwinter in New Mexico. The Greater Sandhill Crane (Grus canadensis tabida) spends the winter on the Rio Grande at the Bosque del Apache NWR. The Lesser Sandhill Crane (Grus canadensis canadensis) congregates at the Bitter Lake NWR on the Pecos River.

In the spring, the Greater Sandhill Cranes migrate to their breeding grounds in the Rocky Mountain region while the Lessers keep flying northwest, headed for western Alaska and Siberia.


During the day, Sandhill Cranes forage in tilled fields.

Sandhill Cranes Forage for Waste Grains and Bugs in Farm Fields

I watch the Sandhill Cranes take off at sunrise, flying south along the river. “Where do they go?” I asked Bill Flynt, the Visitor Center volunteer. “Head out the Old Dexter Highway,” he told me. “You’ll find them in the farm fields out there.”

I followed the birds south and, just as predicted, found them feeding in a tilled field. Sandhill Cranes feed on seeds, grains, grasshoppers, and pillbugs. I suspect that before the conversion of grasslands to farm fields and desert scrubland, the Sandhills lived primarily on grass seeds and grasshoppers. But these days, they’re dependent on domestic crops such as waste grain or corn left in the fields after harvesting.  They’ll also eat sorghum and sprouting alfalfa which can be a problem for the farmers.

As the local dairy industry grows, the traditional corn and grain crops are replaced by alfalfa, causing a decline in the overwintering populations of Lesser Sandhill Cranes at the Bitter Lake NWR. Refuge scientists believe that the birds are simply moving on as they deplete their local food resources.

Black silhouettes against the evening sky, Sandhill Cranes return for the night.

The Evening Fly-In

My last evening at the refuge, I watch as the Sandhill Cranes begin to fly in. Their loud bugles can be heard for miles. Sometimes I hear them coming long before I can spot them in the sky. This time, they settle far out in the middle of the ponds. I can see them, I can hear them, but I can’t photograph them. That’s okay. It’s time just to sit and watch this amazing wonder of nature.

Also posted in Birds, New Mexico Tagged , , |

Ghosts of the Past: Marine Fish on Mimbres Pottery

Porpoise on Mimbres Bowl from the  Deming Luna Mimbres Museum, New Mexico

In the far southwestern corner of New Mexico is a treasure. The Deming Luna Mimbres Museum, housed in the 1916 Armory Building, has collections that include a lot of just about everything. Who knew someone collected buttonhooks and that they could be so interesting? This is the thing about the museum: it’s easy to get distracted.

I visited on a windy, cold, spring day last week with pretty much one goal in mind. I’d heard about their collection of Mimbres artifacts and, as an archeologist, I just couldn’t resist an exhibit like that. I got a bit lost in the doll collection (there wasn’t a way out), wandered past cabinets of porcelain and fine china, meandered down a narrow hall, and then took a left into a room of wonders. Glass cases held ceramic bowls, pots, and bean jars of all shapes and sizes, trays of tiny beads, arrowpoints, bone tools, and fragile cord used for snare traps. I made the rounds, once, twice, and then just stood there, listening to the stories whispered by the pots.

The Mimbres Room, Deming Luna Mimbres Museum, New Mexico

The Mimbres people lived in the Mimbres River valley of southwestern New Mexico. For about 200 years (between AD 950 and 1150) they produced distinctive black-on-white pottery that told the story of their lives—men setting snares and carrying rabbit sticks, women giving birth, and people swimming with a school of fish. Many of the bowls have a single animal carefully painted on the bottom: a frog, bird, pronghorn antelope, or fish.

At first, you think that the animals are simply abstractions, the essence of the animal. But when you look closer, you begin to notice details and you eventually realize that the little fat bird with the tear-drop shaped circle around its eye must be a Montezuma Quail. Which is interesting, because Montezuma Quail don’t occur in that region today. But neither do the fish.

Quail BowlMontezuma Quail

Stephen Jett, a geographer from the University of California, Davis and his colleague Peter Moyle, a fisheries biologist, got interested in the fish represented on Mimbres pots and wrote a paper titled “The Exotic Origins of Fishes Depicted on Prehistoric Mimbres Pottery from New Mexico” (American Antiquities 51(4), 1986, pp 688-720).

About 11% of the animals shown on Mimbres pots are fishes and, as early as the 1950s, researchers noted in passing that many of the fish weren’t what you’d find in the Mimbres River. In fact, they kind of look like something you’d see in the ocean. But as any geographer will tell you, southwestern New Mexico is a long way from the ocean. A very long way away.

Jett funneled every fish image that he could find to Moyle and asked a simple question: What do you think this is? Surprisingly, Jett and Moyle discovered that they could identify many of the fish and that the majority of the fish species painted on Mimbres pots were marine in origin. Jacks, giant jewfish, snappers, grunts, and the distinctive long-nosed butterfly fish were carefully painted by the Mimbres. The Pacific razorfish—with its distinctive “unicorn” fin—is clearly depicted along with tiny blennies, and giant parrotfish.


Of course, the million dollar question is “How in the world did the Mimbres people know what long-nosed butterfly fish and Pacific razorfish looked like?” But before we answer that question, there’s more you should know.

The Mimbres were apparently fascinated by the ocean. Dozens of clam shell bracelets and hundreds of tiny shell beads fill the trays and cases of the Mimbres rooms at the Deming Luna Mimbres Museum. Thousands of shell items—from at least 11 genera of seashells—have been recovered from Mimbres archeological sites in the region.

Ancient seashells found in a Mimbres site in southern New Mexico.

Conventional wisdom is that all of the shell jewelry originally came from the Hohokam, a contemporary cultural group that lived in south-central Arizona and were believed to control the shell trade. They obtained their raw materials from the Gulf of California and the Pacific coast, ground the shell down to create bracelets, tinklers, pendants, and beads, and then traded them to the Anasazi to the north and the Mimbres to the east.

But Jett and Moyle weren’t quite so quick to accept conventional wisdom. The fish on the pots, they say, indicate that the Mimbreños were very familiar with the ocean and were most likely active participants in shell collecting and transportation. By looking at the species of fish and the types of shell, they concluded that the Mimbres people were making trips to the Gulf of California and specifically, the area around Guaymas, Mexico. Near Guaymas both the reefs necessary for the fish species depicted on the pots and the sandy beaches where the shells could be collected are found.

To the modern human, the thought of walking 1000 miles or so to the coast and back is a bit daunting. But to the Mimbreños? Probably not so much. A trip of that distance would only take a couple of months by foot and there were undoubtedly villages (and trade opportunities) along the way. The marine archeologist in me also has to wonder if they used canoes or some type of water transportation to speed up the journey (although I couldn’t find any images of boats on the pottery I saw).

Because there’s little evidence that the Mimbres people either traded their pottery or imported pottery from other places, they must have painted their fish pots when they returned home. Did they sketch the different types of fish on pieces of bark and take them back to show the potters? Or did they memorize details to paint later?

The pots in the museum whisper to me, but they keep some secrets to themselves.

Deming Luna Mimbres Museum | 301 S. Silver Ave., Deming, New Mexico | 575.546.2382 |


Jett, S.C. & P.B. Moyle. 1986. The exotic origins of fishes depicted on prehistoric Mimbres pottery from New Mexico. American Antiquities 51(4):688-720.

Parks-Barrett, M.S. 2001. Prehistoric Jewelry of the NAN Ranch Ruin (LA15049), Grant County, New Mexico. Master’s thesis, Department of Anthropology, Texas A&M University.

Images from the collections of the Deming Luna Mimbres Museum.

Also posted in Animals, Archeology, Fish, New Mexico Tagged , , , |

Monarch Conservation in West Texas

Monarchs roost in a pecan tree in Alpine, Texas

The sun is setting as I sit on the picnic table and just watch. Monarchs swirl around me by the hundreds—or is it thousands? They begin to settle, landing in rows on the bare branches of the old pecan tree near Kokernot Lodge in Alpine. They’re restless though, and burst into flight again when a newcomer tries to squeeze into the row. A swirl or two and they resettle on a clump of leaves. More butterflies float in from the north and jostle for space. I am amazed by the utter silence. A butterfly wing doesn’t even whisper.

Monarch Migration
Monarchs are one of the few insects that migrate in great round-trip journeys from their summer breeding grounds in the north, to sites in the south where they overwinter. In the spring, they head north again. The earliest report of monarchs migrating south was published in a Canadian journal in 1857. The author, W.S.M. D’Urban, noted that monarchs appeared in the Mississippi Valley “in such vast numbers as to darken the air by the clouds of them.” But it took another 120 years to discover where they were going.

In the late summer, as the nights grow cooler and the days grow shorter, a generation of monarchs emerges from their chrysalides that are biologically and behaviorally different from the generation before them. These monarchs won’t mate or lay eggs until the following spring. Their driving instincts are to find food and fly south.

They travel in pulses, often driven by cold fronts that bring the wind from the north, sometimes traveling 150 miles in a single day. Late in the afternoon, the butterflies seek a place to spend the night—in Texas, this is usually a pecan or oak tree near water. Although monarchs do not migrate in flocks as birds do, individual monarchs seem to seek each other out to form roosts of hundreds to thousands of butterflies. The next day, warmed by the morning sun, they will continue their journey south.

When the winds are unfavorable, monarchs stay on the ground, nectaring on goldenrods, gayfeather, and mistflowers. These nectaring stops allow the monarchs to build up fat reserves that will sustain them throughout the winter.

By late September, all of the monarchs from the 5.2-million-square-mile breeding grounds east of the Rocky Mountains funnel into Texas. Most years, the monarchs will travel through Texas along the central flyway, a broad swath of land 300 miles wide and centered on a line between Wichita Falls and Eagle Pass. They are headed for the fir forests of the Transverse Neovolcanic Belt near Mexico City, a place that none have been before, but that millions will find.

Monarch Conservation
D’Urban’s skies darkened by clouds of monarchs are pretty much gone. In fact, some predict that the great monarch migration may be a biological phenomenon that winks out in our lifetime. Illegal logging of forests in Mexico, changing climate in both the overwintering grounds and the summer breeding grounds, and the decrease in nectar and larval host plants are all taking their toll.

A world without monarchs scares people, so many organizations and agencies are jumping on the monarch conservation bandwagon. Yesterday, Texas Parks and Wildlife Department released the Texas Monarch and Native Pollinator Conservation Plan (October, 2015) or perhaps better titled The I-35 Monarch Conservation Plan. Don’t get me wrong. I’m proud of TPWD and the many partners listed in the report for recognizing the critical role that Texas plays in monarch conservation and for wanting to do something about it. But—ahem—that beautiful flyway map produced by Monarch Watch? It’s just an average. Monarchs scoff at sharp lines on human-drawn maps. This year, thousands are monarchs are passing through Fort Davis, Alpine, Marathon, and Terlingua on their way to Mexico. As they have in the past and they will in the future.

Fall Migration 2015

Journey North map of the 2015 Fall Monarch Migration


This particular pet peeve of mine is not new. About 10 years ago, I read an article about a monarch tagging project being conducted by the Southwest Monarch Study of Arizona. They were finding that many of their monarchs chose to overwinter in sunny California rather than Mexico. This got me thinking about the Trans-Pecos monarchs. Where were they going?

I eagerly contacted the Southwest Monarch Study and asked to be part of their tagging program. “You’re too far east,” they told me. “Contact Monarch Watch.” Monarch Watch told me to contact Texas Parks and Wildlife and Texas Parks and Wildlife told me we were too far west for our monarchs to be of any interest.

I gave up, but the monarchs haven’t. In fact, the frequency of the monarch migration through west Texas seems to be increasing. Don’t quote me on this. It’s just a hunch without any supporting data. But it is an interesting research question. How does the monarch migration fluctuate over time and what are the triggers that cause a shift of the central flyway? What does long-term climate research predict for our region? Will El Nino patterns increase in frequency, resulting in wetter Fall weather and increased nectar sources for monarchs?

Conservation plans need to be pro-active and prepare for a changing future. I know that it’s easiest to focus on what we see today and concentrate on urban areas because funding is often about numbers (how many school children can you reach per dollar spent?), but if you’re truly interested in monarch conservation, think broadly and include west Texas in your planning.

In the meantime….
As I climb off my soapbox (will someone please hold the ladder?), I have some suggestions:

1) Plant for fall migration. You’ll read a lot about the need to plant milkweeds for monarchs. Milkweeds are important, it’s true, but in the fall, monarchs need nectar sources. A 2006 study of lipids (energy storage molecules) in migratory monarch butterflies showed that once monarchs get to Texas, they pause to nectar and build up their lipid reserves before continuing on to their final destination in Mexico. These lipid reserves are critical to their survival over the winter. Texas wildflowers are critical to their survival over the winter.

2) Go to the Big Bend Chapter of the Native Plant Society of Texas Facebook page and post an image of plants that you’ve seen monarchs use for nectaring. Let’s develop a list specific to this area for homeowners, landowners, and government officials that can be used for everything from large-scale restoration projects to home gardens.

GoldeneyeGregg's MistflowerAnnual Goldeneye
Texas GayfeatherMilkweedThistle
Fall blooming flowers such as sunflowers, mistflower, Annual Goldeneye, Gayfeather, milkweeds, and thistles provide important nectar sources for migrating monarchs.


3) While we would all like to think that our backyard gardens are Making A Difference, here’s what the 2006 monarch study has to say: “The popularity of butterfly gardens and native plant landscaping may enhance pollinator populations locally, but will never be of sufficient magnitude to compensate for the losses of native nectar sources from rural habitats.” Damn.

This isn’t to say that you shouldn’t be planting your monarch café. Please do. But also think bigger. Did you know that there are over 4 million miles of roadsides in the United States? I don’t know how many in Texas, but I’ve driven over 1,000 of these miles within the last week, so I can tell you that there’s a bunch. Thousands of miles of roadsides fenced off from grazing animals and protected from development.

The Texas Department of Transportation is responsible for managing these roadsides. They even have a wonderful document titled Roadside Vegetation Management Manual: Guidelines for Levels of Vegetation Management. Take a look at it. It’s great.

Unfortunately, when I called TXDOT one year to register a complaint about the mowing of a huge stand of gayfeather in full bloom, I was told the guidelines are “suggestions, not policy.” I think Texans and Texas deserve better than that. Make yourself familiar with the guidelines and work with your local TXDOT office to let them know that you care.

3) Post observations to Journey North. The only way they’ll know about the monarchs of west Texas is if we tell them.

Also posted in Insects, Plants

Ghosts of the Past: Mexican Grey Wolf

Mexican Grey Wolf in the El Paso Zoo, Texas.


I believe in ghosts. They hide in plain sight, urging us to listen to the stories they have to tell.

Ash, a Mexican Grey Wolf paces in her enclosure at the El Paso Zoo. She circles through the shrubs, down a slope and back around the rock-lined pond. She pauses for a few seconds to stare at me and then continues her pacing. Ash may not know it, but she’s one of the last of her kind.

Mexican grey wolves such as Ash and her companion, Ivy, were once common throughout the mountain woodlands of central Mexico,  Arizona, southern New Mexico, and southwestern Texas. Vernon Bailey, in his Biological Survey of Texas (1905) describes the grey wolf as “still common over most of the plains and mountain country of western Texas.” But even in the early 1900s, grey wolves were being hunted by ranchers and professional wolf hunters. Bounties were high and wolf hunting was a profitable business. “There is a strong temptation,” says Bailey, “for the hunters to save the breeding females and dig out the young each year for the bounty, thus making their business not only profitable but permanent.”

Not quite permanent, though. In 1972, Dr. James Scudday published a brief report in the Journal of Mammalogy about two young wolves that were trapped in Brewster County in December, 1970. These were the last grey wolves seen in west Texas and pretty much the last seen in the southwest north of the border.

The Mexican grey wolf was put on the endangered species list in 1976 and captive-bred wolves—descendants of breeding stock captured in Mexico—were used to reintroduce the species to the wild in the Blue Range Wolf Recovery Area of New Mexico in 1998. The recovery program has proceeded in fits and starts. Reintroduction of a predator such as the grey wolf has not been enthusiastically embraced by rural and ranching communities, making it an often contentious political, rather than ecological, issue.

Jason Mark, takes a look at both sides of the issue in his fascinating essay Can Wolves Bring Back Wilderness (Scientific American, Oct. 9, 2015).

“Can we find a way to live with the wolf’s wildness and share space together?” questions Mark. “Can we coexist, and come to see another carnivore as something of an equal, and not just an enemy? Or do we have to control it, and in that control limit its wildness, the very thing that draws us to it?”

Will the Mexican grey wolf always be shimmering and barely visible–a ghost from our ecological past?



Also posted in Animals, Texas Tagged , , , |

Just Add Water: Annual Wildflowers in the Chihuahuan Desert

Prairie evening primroses dot a pasture near Fort Davis, Texas.

My friend, John Karges, and I were talking yesterday about the amazing spring that we’re having. He laughed and said “Add water and the desert will stir itself.”

How true.

We’ve had an extraordinarily wet winter and spring this year. Deep, soaking rains and frequent snow (and ice) storms encouraged a wildflower display that few can remember ever seeing in the Chihuahuan Desert region. Big Bend bluebonnets create a blue haze on the hillsides; the delicate, white petals of prairie evening primrose look like a tissue-box explosion in pastures; and mustard plants emit a perfume so sweet it’s cloying at times.

Big Bend Bluebonnets along the River Road in Presidio County Texas.

Even the stems of the cacti are so swollen with water they look like they’re going to burst. Instead, they’ve burst with flowers, dozens of blossoms covering a single plant.

The desert is in bloom. It’s a marvelous sight to behold.

Mustard wildflowers carpet a pasture in the Chihuahuan Desert near Marathon, Texas.

But where do all these flowers come from?

Most of the time, the Chihuahuan Desert is a pretty harsh environment. It’s dry (especially in the winter) and the rain that we do receive tends to come in the summer during highly localized thunderstorms that may drench one spot but leave a broad area dry as a bone.

To cope with the heat and the unpredictable precipitation patterns, desert plants have an amazing array of adaptations aimed at holding on to moisture: small leaves, fine hairs that protect the leaf surface, and a splendidly specialized photosynthetic process.

But during years like this one, we’re reminded of the most amazing adaptation of all: being an humble annual.

Annual plants are those that go from seed to seed in a very short time. When conditions aren’t favorable, the seed just doesn’t sprout. It sits in the soil, waiting for the perfect combination of moisture and warmth that will increase its chances of survival.

Dense patches of the annual wildflower curvepod scrambled eggs were common at higher elevations in the Chihuahuan Desert.

This life cycle isn’t unusual—in fact, approximately 13% of the world’s flora consists of annuals. But if you look at the flora of a typical desert, you’ll find something very different. In the aridlands of the world, annuals can make up 40% or more of the desert flora. Think about it. Nearly half of the plants growing in a desert won’t even make an appearance until there’s some hope of surviving long enough to be pollinated and set seed.

The seed of many desert annuals can survive for years—decades even—before the conditions are perfect for growth. On occasion, they get fooled, though. A good soaking rain followed by heat, wind, and dry conditions may spell doom for an overeager annual.  Long-term survival depends on mechanisms that discourage a portion of seed from growing even when conditions are just right.

But sometimes, spring conditions are just too favorable for any plant to remain snug in its seed jacket. This is one of those years. Good rains and warm day-time temperatures have encouraged the growth of hundreds of thousands of annuals. Early in the spring, clay flats in the Big Bend region were covered with turtleback—its gray-green leaves and cream-colored flowers forming a soft carpet across the landscape. Stands of lyreleaf twistflower (you’ve just got to love the name) sent their spikes of purple, urn-shaped flowers above the grasses, and curvepod scrambled eggs had even the plant enthusiasts scratching their heads. Where did they all come from?

Naked turtleback creates a green haze in the Chihuahuan Desert of Big Bend National Park, Texas.


Naked turtleback in the clay flats of Big Bend National Park, Texas.

The desert is truly spectacular this year and every week it changes. We’re still getting rain, so the show will go on. If you’ve been putting off your annual pilgrimage to the Chihuahuan Desert, it’s time to quit procrastinating, pack your camping gear, and come on out. This truly may be a once in a lifetime experience.

Also posted in Landscapes, Plants Tagged , , , |

Chihuahuan Desert Ferns

Cheilanthes fern, Fort Davis National Historic Site, TexasNormally, I’m outside every day in September enjoying the cooler temperatures, brilliant sunshine, and abundant life inspired by the afternoon thunderstorms of the monsoon season.

But not last week.

Rain (torrential at times), heavy cloud cover, and temperatures in the low 50s kept me huddled in the house muttering about the imminent arrival of the next Ice Age. As I stared morosely out the window, watching the rain drip from the roof, I began to wonder: What happens to the butterflies, bees, and bugs when the temperatures go from warm and dry to cool and wet in a single day?

Thinking this was the perfect subject for a blog (I’m sure you’ve all been dying to know), I donned my rain jacket, grabbed my camera gear, and wandered through the mist to the Fort Davis National Historic Site. Although chiefly known for the 19th century fort buildings, they also have a wonderful nature trail that loops from the fort site, up the ridge that separates the Fort from Davis Mountains State Park, and back down again. Here, I was sure I would find my sleeping bugs.

I probably would have, too, if I hadn’t gotten distracted. Every place I peered and poked for insects, I was confronted by ferns. Beautiful, lush, green ferns. The magic of desert rain.

Dancing Bommeria, a Chihuahuan Desert fern, growing near Fort Davis, Texas.Most people don’t hot-foot it to the desert to look for ferns. But perhaps they should. According to botanists Sharon Yarborough and Mike Powell, there are 64 different types of ferns that grow in the Trans-Pecos region of Texas.

Ferns can grow in the desert because they’re experts at finding little microhabitats that are just a tinier bit wetter than the surrounding landscape. Look for them growing from cracks in the rock, under the shelter of a tree, or peeking out from beneath a boulder. Depending on when you look, though, you may not be overly impressed. In fact, during most of the year, desert ferns are brown, crispy, and look—well—dead.

Chihuahuan Desert ferns dehydrate during the warm, dry months and wait for rain.But fear not! Playing dead is just one of the many adaptations that ferns have for surviving in the desert. And what an adaptation it is. Your average plant can drop to about 75% moisture content before it begins to wilt and beg for water.  Creosote, one of our common desert shrubs, can lose about half its moisture before it begins to look a bit peaked.

But the ferns. Oh, the ferns. They are the masters of dehydration. During the dry season, some species can desiccate to less than 6%—or as dry as many seeds—but begin to green up, unfurl, and grow within an hour after a refreshing rainfall. When it dries up again, so do the ferns.

But ferns don’t give up their moisture easily. They may be able to survive as a brittle frond, but life is better when you’re green and photosynthesizing. So to stay green as long as possible, the ferns (and many other desert plants) have ways to reduce moisture loss.

Small Leaves

Small Leaves

Waxy Coating

Waxy Coating

Protective Hairs

Protective Hairs

Thickened Leaf Margins

Thickened Leaf Margins

Small is better. Most desert ferns are much smaller then their rainforest cousins. Remember that during the process of photosynthesis the plant takes in carbon dioxide and releases oxygen and water as a waste product. The smaller the leaf, the less water is released.

Be waxy. Most water is lost (transpired) from special cells on the leaf called stomata. These open and close to absorb and release gases (carbon dioxide, oxygen, and water). But other parts of the leaf surface and stem can lose water through simple evaporation. To help protect from this “incidental” water loss, many of the ferns have a cuticle of waxy deposits on the leave surface that make them thicker and seal in the water.

Get hairy. Have you noticed how many ferns are grey and fuzzy? If you look closely, you’ll notice that the color is due to a dense coating of hair. These light-colored hairs serve a couple of purposes. First they reflect light making the leaf surface temperature cooler and they efficiently trap rain, dew, and other forms of moisture to raise the humidity around the leaf surface. Keeping the air surface immediately around the leaf cooler and more humid reduces the evaporative demand from the atmosphere.

Thick leaf margins. The last defense against moisture loss is the ability of the leaflets to roll, thus protecting the surface and the spores. Many fern leaflets have thickened margins that enhance the ability of the leaf to roll.

Not all ferns found in the desert have these adaptations for dry conditions, though. Others simply seek places where there is enough moisture. Delicate maidenhair ferns, for example, can be found on many shaded rock faces with perennial seep springs. You can find these beautiful ferns at the bottom of Modesta Canyon at the Chihuahuan Desert Nature Center or in the grotto at Ojito Adentro, Big Bend Ranch State Park.

Water Clover (Marsileaceae) is a Chihuahuan Desert fern that grows in puddles during the rainy season.But my favorite fern is the water clover. This aquatic fern survives the dry season as a packet of spores (sporocarp) in the mud of ephemeral pools. When the rainy season arrives and the pools fill with water, the gelatinous interior of the sporocarp swells, rises to the water surface and splits, releasing the male and female spores. Once they do what males and females do, the newly fertilized embryo sinks to the bottom of the pool, takes root and begins to grow, eventually spreading its four leaflets across the surface of the pool to begin the cycle of life again.

It’s starting to rain. Time to go look for ferns!

Also posted in Plants Tagged , , , , |