Jump to main content

Habitats of the Llano Estacado
Playas

Introduction

Playas are small, rounded, shallow temporary bodies of water with gently sloping sides and clay soil basins. Thousands of playas (96% of all playas in the world) dot the Llano Estacado. Playas are a major source of biological diversity and host a distinctive mixture of plants and animals in every season. They provide wetland habitat for waterfowl, shorebirds, and many other animals in a semiarid environment. Most playas are usually dry, sometimes for several years. Periodic flooding and drying results in a more diverse and productive community of plants and invertebrate animals, providing food and cover for a variety of both resident and migratory wildlife.

Formation

Playa basin soils are predominantly clay and are similar regardless of their location on the Southern Great Plains. This fact reflects similar processes in their formation and development. Any depression on the High Plains surface that periodically stores and transmits water to the subsurface may develop into a playa. Most of the Llano Estacado topsoil is underlain by a layer of thickened calcium carbonate called the caprock caliche. Standing water in a low spot initiates the processes of playa formation.

Plant growth in a depression allows the accumulation of organic matter. This organic matter is carried below the basin soil as water percolates to the subsurface. The organic matter is oxidized and carbon dioxide gas is released which in turn reacts with the infiltration water to form carbonic acid. Carbonic acid then dissolves the caliche causing the playa basin to sink lower.

Many playas have lunette shapes on their east and south sides indicating that wind may have a factor in playa maintenance by removing naturally collected sediments. Low areas that collected water also attracted herds of large mammals such as giant bison, modern bison, mammoths, mastodons, horses, etc. Animal herds were not only attracted to the water, but also to the mud for wallowing, probably transporting large amounts of basin soils out of the depressions. There is no scientific consensus on the relative importance of the individual factors in playa origin and formation, but there is agreement that several forces are at work.

History of Playas

Humans have used playas on the Llano Estacado for water and hunting big game for thousands of years. Paleolithic hunters killed and rendered mammoths and giant bison around playas. Playas were also important hunting sites for the Apache, Comanche, and Kiowa because of the bison, pronghorn, and mule deer attracted to the water. From the 1770’s until the 1870’s, ciboleros came from Santa Fe, Taos, and El Paso to hunt bison for meat and to secure hides for the Santa Fe-Chihuahua trade. They often camped near a rain-filled playa while hunting. Playas were also important to Anglo explorers, American military expeditions, freighters, ranchers, and settlers. Amarillo, Texas was established because of the close proximity to a perennially filled playa.

Prehistory

Since there is not a major river on the Llano Estacado, Paleolithic hunters used playas as sources of water and game. Projectile points found with mammoth bones in shallow lake deposits near Miami, Texas may indicate that playas were used for trapping and attracting large animals.

Humans coexisted with and hunted large, but now extinct, mammals between the late Pleistocene and early Holocene epochs between 12,000 and 8,000 years BP. The first discoveries of human occupation of North America cane from the Southern High Plains of eastern New Mexico at the Clovis and Folsom sites in the 1920s and 1930s. Numerous other sites have since been discovered throughout the High Plains at Lubbock, Midland, Plainview, Milnesand, Nall, Lipscomb, and San Jon.

Pueblos, Apaches, Comanches, and Kiowas

Traces of pole-frame houses and pottery shards were found on a knoll west of a playa at the Laguna Plata site in New Mexico. The pottery shards were consistent to a type Pueblos used between 1250 and 1350 AD. Native Americans inhabiting the Llano Estacado playas prior to 1838 included the Apache, Comanche, and Kiowa. Playas on the High Plains also attracted hunting parties from the New Mexico Pueblos and the Wichita from the Rolling Plains to the east. When playas contained water many species of game animals and predators were attracted. Bison and pronghorn were most common. Other large mammals that used playas included elk, mule deer, and gray wolf.

As Americans of European descent began to spread across the Plains, the vast herds of grazing animals and their associated predators were greatly reduced if not altogether eliminated. Between 1836 and 1879 the Comanche fought advancing Texas settlers and ranchers. The Comanche sought refuge from Texas Rangers and the U.S. Army around isolated permanent playas and canyons.

Ciboleros

“As we were proceeding on our march, we observed a horseman approaching, who excited at first considerable curiosity. His picturesque costume, and peculiarity of deportment, however, soon showed him to be a Mexican Cibolero or Buffalo-hunter. These hardy devotees of the chase usually wear leathern trousers and jackets, and flat straw hats; while, swung upon the shoulder of each hangs his carcage or quiver of bow and arrows. The long handle of their lance being set in a case, and suspended by the side with a strap from the pommel of the saddle, leaves the point waving high over the head, with a tassel of gay parti-colored stuffs dangling at the tip of the scabbard. Their fusil, if they happen to have one, is suspended in like manner at the other side, with a stopper in the muzzle fantastically tasselled.”

Josiah Gregg,
Commerce of the Prairies, 1844

Toward the late 17th century, ciboleros (Mexican bison hunters) arrived on the Llano Estacado from the areas around Santa Fe, Taos, and El Paso to hunt bison for meat and sport. They became instrumental in providing meat for a growing New Mexican population and hides for the Santa Fe-Chihuahua trade.

Cibolero expeditions onto the Llano Estacado often included as many as 150 people–cazadores (hunters) rode into bison herds armed only with lances, killing 8-25 bison each in a single foray. Ciboleros were dependent on the speed, agility, and skill of their horses for their safety. Meat would be cut into strips for drying and curing, hides would be tanned, and both loaded onto ox-drawn carretas (carts) for the return trip to New Mexico, often camping near playas for a source of water.

The Plains Indians occasionally fought against the ciboleros throughout the 19th century in protecting their hunting interests. The ciboleros learned to bring trade items so the Indians did not resent their intrusions as much. The cibolero life survived until the Anglo hunters decimated the bison herds in the late 1870s.

Major Landmarks

September 29, 1849–“Leaving the sand this morning, we pushed out upon the high plain of the Llano Estacado, not knowing whether we were to find water before we reached a laguna about sixty-five miles distant…I therefore sent a party in advance to search for water, and felt some anxiety as to the result; I was relieved, however, about 11 o’clock, when a messenger returned with the cheering intelligence that the party had found a large pond of good water about sixteen miles from where we left this morning…

From the sand hills our road followed an old Comanche trail until we turned to the left, two miles from our present camp. The track we made is plain, and travelers will have no difficulty in following it to water. We are near two ponds in the prairie, where, judging from present appearance, there will always be water found, except in the dry season; the grass is good. Our course from the sand hills is N.57° E., and the distance fifteen miles and three-tenths.”


From the journal of Captain Randolph B. Marcy
United States Army, Fifth Regiment Infantry

Historically, some playas permanently held water and were important to European explorers, American military expeditions, freighters, ranchers, and settlers. Amarillo, Texas was established because of the location’s proximity to a perennially filled playa.

Ogalla Aquifer

Most of the crops in the Western Great Plains depend on irrigation for successful production because of unpredictable and scarce precipitation. Irrigation is possible because of the presence of the world’s largest aquifer–the Ogallala Aquifer. The Ogallala Aquifer underlies much of the Western Great Plains from South Dakota to the Llano Estacado of Texas and New Mexico.

Given the current rate of water use, much of the Great Plains could see extreme water shortages by the year 2020 with potential social and economic consequences. One of the more important discoveries about the value of playas is that they are true “recharge” wetlands. On the Southern High Plains, playas appear to be the only sites for recharging the Ogallala Aquifer.

Evolving Relationships between Humans and Playas

“...perhaps the most important value of playas is to the human condition. Humans need nature and to connect with other life on Earth.”

Loren M. Smith, Caesar Kleberg Professor of Wildlife Ecology
Texas Tech University
From Playas of the Great Plains

In the past, playa wetlands were largely viewed as impediments to agriculture and as sources of disease. Many playas had reuse pits dug into them to concentrate water into a smaller area for livestock and the basins converted into farmland. We now have a better understanding of the important ecological and economic roles of playas. Both wet and dry playas provide wildlife habitat for many species. Landowners can lease their land for hunting, wildlife viewing, and education. Multiple uses of the land also boost rural economies.

In urban areas, playas are used for storm water flood control management and numerous recreational opportunities. Runoff has transformed many urban playas into permanent lakes supporting biotic communities largely dominated by exotic species. These urban wetlands generally support a park system that ultimately provides income for local economies.

Playas are also important as scientific study models. With more than 35,000 playas over the vast area of the Great Plains, all playas have similar hydrology, shape, size, and soil type. They are ideal models for broad-ranging ecological studies.

Ecology of Playas

Playas are usually small, round, shallow, temporary bodies of water with gently sloping sides and clay basins. Playas are a major source of biological diversity and host a distinctive mixture of plants and animals in every season. They provide wetland habitat for waterfowl, shorebirds, and many other animals in a semi-arid environment. Plants and animals living in and around playas must be adapted for periodic flooding and drying. Playas are often dry for several years depending upon local rainfall patterns. This periodic flooding and drying results in a more diverse and productive community of plants and invertebrate animals, providing the necessary food and cover to support a variety of both resident and migratory wildlife.

Mammals

Because of the ephemeral nature of playas, aquatic mammals rarely occupy them; however, mammal populations associated with the margins of playas can be diverse and abundant. Various migratory bats feed on insects emerging from playas. White-tailed deer, mule deer, and pronghorn are commonly found around playas. Because playas often form the only habitat in an intensive agricultural environment, cottontail rabbits and native rodent populations reach relatively high densities. Mammalian predators such as coyotes, raccoons, and striped skunks also show preference for playa habitat. Prairie dog towns can often be found on the slopes of playas, which serve as a major refuge for the declining population.

Amphibians and Reptiles

In winter, and when playas are dry, most amphibians are dormant in the playa sediments, and can remain so for years with their future dependent on proper moisture conditions to emerge. In wet times the amphibian community is dominant during the early summer. Amphibian numbers can easily overwhelm all other vertebrates. A plains spadefoot toad can hatch in as little as 20 hours in warm weather and metamorphose from tadpole to adult in less than 13 days.

Tens of thousands of larval tiger salamanders can occur in a single playa covering a couple of hectares. A reproducing tiger salamander may lay more than 5,000 eggs in a clutch. A single Great Plains toad can lay more than 40,000 eggs in one clutch and can produce two clutches a year. The sheer magnitude of amphibian biomass and abundance is key to the survival of predators such as dragonfly larvae and black-crowned night herons.

There are few native reptiles occurring in the inundated portions of playas. The yellow mud turtle is the main exception, with a distribution coinciding with the distribution of most playas. In dry times, the yellow mud turtle can aestivate for as long as two years. The reptile community in dry playas, or on the interface of the water and associated watershed, can be roughly as diverse as the amphibians, although not nearly as dominant.

Plants

Playas have a flora that is unique to them. Algae are at the base of the food web in playas. Green algae play an essential role in maintaining the supply of oxygen used by aquatic organisms. The primary influence on plant species composition in playas is hydroperiod. A playa that is dry in the early spring can have an entire flora turnover if the basin receives substantial rain and becomes inundated. Plants adapted to playas typically have long-lived seed banks or hardy underground structures that can take advantage of variable amounts of water in a short time. A dry playa may be dominated by buffalo grass in the early spring, but after the rain is replaced by arrowhead.

Birds

The greatest abundance and diversity of avifauna in the playas generally occurs during the spring and fall migrations. Playas throughout the Great Plains serve as important migration habitat for more than 30 species of shorebirds. Their preferred playas lack dense stands of emergent vegetation and have mudflat banks where they spend most of their time feeding. Shorebird diets consist mostly of invertebrates and seeds of wetland plants. American avocets, killdeer, and black-necked stilts nest along sparsely vegetated shorelines and avoid densely vegetated playas.

The number and diversity of waterfowl using playas during migration is spectacular. Millions of waterfowl of at least 25 species use playas during migration. Ducks and geese largely feed in the surrounding agricultural fields. Dabbling ducks are most common and generally nest in dense vegetation of dry playas or in the upland immediately surrounding a playa. Diving ducks are fewer because most playas are too shallow.

Other birds are also attracted to playas. Swallows feed on the abundant source of insects. Whooping cranes, bald eagles, and black terns use playas during migration. American coots, pied-billed grebes, and black-crowned night herons also nest. Depending on the composition of vegetation, the nesting community varies in dry playas. Red-winged blackbirds use curly dock as a primary nesting substrate. Meadowlarks and northern bobwhites nest in dry basins with mid-height grasses. Cassin’s and grasshopper sparrows prefer shorter to mid-height grasses. Many raptor species such as golden eagles and peregrine falcons are attracted to playas in the winter to feed upon other birds and mammals.

Invertebrates

The diversity and abundance of invertebrates far surpasses that of the vertebrates. The amount of emergent vegetation in a playa has the most influence on invertebrate diversity by providing habitat, food, and cover. Many invertebrates, such as fairy shrimp eggs, can remain dormant in playa sediments for decades. The response of invertebrates to a playa filling with water after a rain can be astounding. Dragonflies can locate a playa within a few hours after filling. Within days after a playa basin fills, the water surface is teaming with invertebrate activity. The invertebrates are a major food source to thousands of resident and migratory birds and other animals.

Related Resources

The following resources for learning more about the Playas habitat are available on this website:

Overview

  • Playas and Playa Lakes - This introduction requires either Microsoft PowerPoint, or the free PowerPoint Viewer which is available for download from Microsoft's website: Windows | Macintosh.

Photo Essays

Videos

Essays

Habitats Overview | Top of Page

Sibley Nature Center
1307 E. Wadley, Midland, Texas 79705
phone 432.684.6827
email info@sibleynaturecenter.org