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The Nature Center

The Llano Estacado

Habitats of the Llano Estacado
Draws

Introduction

Draws are the headwater drainage patterns that lead to rivers. They are usually shallow (less than 30 feet deep) and narrow (less than 1500 feet across). Draw bottoms often have pocket forests of hackberry and soapberry trees.

Draws often function as travel corridors for wildlife. Wild turkey, white-tailed deer, Virginia opossums, and many other species of animals immigrated to the Llano Estacado in the last 50 years using the draws as their highway system. Animals frequently seek protection from winter storms in draws since they are lower than the surrounding areas.

Plant species from further east, such as bumelia and moonseed vine, can also be found in the draws because the soils are richer and contain higher levels of moisture for longer periods of time. Draws of the Llano Estacado cut through a variety of soil types. The bottoms are often composed of Lipan clay that supports a flora similar to that of playas. Sand fields with shin oak occur on the north and northeast sides of the draws. Draws cutting through rockier soils support little leaf sumac and feather dalea. Downstream, pockets of senescent trees may be found. There may also be clusters of young trees, mature trees, and trees of mixed ages. In some places draws have become choked with introduced salt cedar.

Plants

Hackberry trees are in the elm family with grayish brown warty bark broken into narrow ridges. The netleaf hackberry usually occurs along draws and playas. As a tree, the netleaf hackberry rarely grows taller than 30 feet. The leaves are rough with raised netlike veins on the lower surface. Hackberry trees attract large numbers of migrating butterflies to feed on its sugary sap. Birds and wildlife feed on the small hard fruits in the winter.

The western soapberry attains a height of about 50 feet. It produces globular, fleshy, yellowish, translucent, shriveled fruit. The fruit contains saponin, a substance that produces lather when mixed with water, and was used for soap by Indians and early settlers. Although toxic, the fruit has also been used medicinally in the treatment of fevers, rheumatism, and kidney problems.

Basket flower prefers undisturbed pasture and areas where rainwater collects. It grows in large stands in draws that are spectacular in wet years. Basket flower pollinates in an unusual way. The stamens are very sensitive to touch, so when roving, probing insects make contact with them, they contract instantly, pushing pollen out over the insect to be carried to the next flower.

Moonseed vine climbs fences, hedgerows, and low shrubs in humus-laden soils in the draws. It produces very conspicuous, brilliant red clusters of drupes for fruit. Many species of birds are attracted to and feed on the fruit.

The dark fruit of bumelia is edible, but not very tasty. It produces gastric disturbances if eaten in quantity. Birds, on the other hand, are very fond of bumelia fruit and often eat it as soon as it ripens. Bumelia often grows with live oak, which it resembles, but is not evergreen.

Birds

The yellow-billed cuckoo is more often heard than seen. It frequently sings when storm clouds are building and so is sometimes called the “rain crow.” Unlike European cuckoos, which are brood parasites and lay their eggs in the nests of other birds, yellow-billed cuckoos incubate their own eggs and raise their own young. Yellow-billed cuckoos eat great numbers of insects in pocket forests.

Wood warblers belong to a family of birds found exclusively in the New World. Because of their reliance on insects, northern species fly thousands of miles to winter in the tropics migrating in waves of loose flocks of mixed species. They are very active birds, flitting about in the trees of the pocket forests during migration. Spring migrants for the most part are distinctively marked in courtship plumage. In fall many species have dingy olive-yellow plumage, however, resulting in a confusing array of individuals that look very similar.

The common poorwill is a member of the nightjar or goatsucker family of birds. It roosts on the ground where it is well camouflaged only to flutter up to snatch flying insects from the air and return to its station. The common poorwill lays its two eggs directly on the ground or atop a flat rock where both parents share incubation and chick rearing. The common poorwill is the only bird known to hibernate.

Winter birds are attracted to draws and pocket forests for cover, shelter, and food. It is not uncommon to observe cardinals, thrashers, kinglets, gnatcatchers, titmice, and accipiter hawks that prey on other birds in wooded areas.

Mammals

The fortress home of the white-throated woodrat is a lodge of sticks and stalks, cacti, and rubbish. The nest proper is a cup-shaped structure composed of shredded dry leaves, grass, and weed stems. Well-worn trails lead to openings in the base of the house. Although several houses may occupy a small, desirable patch of cacti, woodrats are unsociable. Only one animal, or a female with young, occupies each house. Woodrats have a habit of taking anything they find desirable, sometimes leaving a pebble in exchange, hence the name “pack rat” or “trade rat.”

Bobcats occupy a variety of habitats, but prefer rocky canyons or outcrops when available. In areas devoid of rocks, bobcats resort to thickets for protection and den sites. They are highly adaptable and in most places have been able to cope with humans. Bobcats are shy and retiring and largely nocturnal. They feed mostly on small mammals and birds.

The porcupine is a large rodent with distinct barbed quills on the back, sides, and tail, and long yellowish tinged guard hairs. It is readily adapted to a variety of habitats. They wander about a great deal and may be found irregularly in seemingly unsuitable areas. On the ground, porcupines seem to be awkward, slow, and methodical, but they are expert at climbing trees. They subsist on green vegetation during the growing season, in large measure on the inner bark of trees and shrubs.

Opossums are among the oldest and most primitive mammals. They are marsupials: the female has a marsupium or pouch on her abdomen for incubating and protecting her young. The young are born as embryos and blindly crawl unaided into the pouch, each attaching itself to a nipple to finish development. Like the bobcat, porcupine, and packrats, they prefer the dense growth of the pocket forests of the draws. The Virginia opossum is more or less solitary and strictly nocturnal. They feed on a variety of things including insects, small mammals, bird eggs, and small reptiles.

Reptiles

The saliva of the regal ringneck snake is apparently toxic to small prey, but is not dangerous to humans. When harassed, the ringneck snake either plays dead or everts its brightly colored undertail. Regal ringneck snakes are seldom seen because they keep to the cover of shrubs or cactus roots and rock crevices. The regal ringneck snake feeds almost exclusively on reptiles, primarily smaller snakes. Prey is grasped and chewed vigorously until immobilized by the salivary toxins.

The desert massasauga is a small, shy rattlesnake that is seldom encountered. It is distinguished from other rattlesnakes by its unique pattern of 9 large plate-like scales on top of its head. They are nocturnal and usually seen in the evenings along the edges of roads or under dead logs in pocket forests within their range.

Skinks have long cylindrical bodies and tails covered with smooth scales and small legs—adaptations for burrowing. Fracture planes in the tail allow the tail to break off easily when grasped by a predator. Skinks are diurnal and females tend their eggs until they hatch. The Great Plains skink is the largest skink in North America. It prefers open rocky grasslands or to be closer to permanent or semi-permanent water sources as might be found in the draws. It feeds on insects, spiders, and smaller lizards. It bites when handled.

Invertebrates

Adult hackberry butterflies rarely stray far from hackberry trees. Usually they will be found sitting on the trunks or branches of the tree or adjacent shrubbery. They do not visit flowers but feed instead on decaying material such as rotting fruit, fermenting tree sap, or animal excrement or carcasses. Both sexes, but especially the males, are pugnacious and vigorously defend their territory.

American snout butterflies have greatly elongated palpi that resemble a snout. They fly rapidly, but settle frequently at mud puddles or to feed on fermenting fruit. The host plants for the early developmental stages of the American snout butterfly are hackberry trees. Occasionally, snout butterflies engage in mass migrations.

Hackberry psyllids are small insects resembling miniature cicadas. Their activities produce galls on the underside of hackberry tree leaves or in the leaf petioles. Galls arise on plants as a result of a parasitic attack. The net result is by an abnormal increase in the number of plant cells or by the plant cells becoming abnormally enlarged. Regardless of the form, a gall is derived completely from the tissues of the host plant.

Chiggers are larval mites. The eight-legged adults are completely harmless, but the tiny six-legged larval stage is parasitic on many animals and humans. There are many species of chigger mites, and their classification is very complex; however, only two species in the United States annoy humans, and neither species transmits any disease. Contrary to popular belief, chiggers do not burrow into the skin, but rather pierce the skin to inject a fluid that liquefies the host’s skin tissues providing food for the parasite. This fluid causes tissue inflammation in the host resulting in an itchy red welt. After becoming fully fed, a chigger drops from its host and goes into the ground to develop into the adult mite that feeds on isopods, springtails, and mosquitoes.

Resources

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

Essays

Photoessays

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