Photo Essay
The Mammals of the Shinoaks
The most common plant in the sanddunes between the Pecos River and the Mescalero Escarpment of the Llano Estacado is the Havard’s Shinoak (Quercus havardii) also known as shinnery. Shinoak is found in deep sands on the Llano Estacado, and to the east of the huge tableland. In some places, shinoak covers the ground’s surface for hundreds of acres. One shinoak plant can cover an area larger than 100 feet by 100 feet. It sends its roots in every direction. If one branch is covered up, another branch will grow and surface again. Species of mycorrhizial fungi help the plant gain nutrients from organic litter of the habitat, and this relationship also seems to change the structure of the soil. Many species of mammals live in the dunes. The tracks and scat of the animals are often visible but to spot the living animal can be a challenge. If you disagree with some of our analyses of the tracks and scat, let us know!
The photographs were taken in late March and early April by members of the 2008 class of the Llano Estacado Chapter of the Texas Master Naturalists. Photographers include Nina McCart, Chris Cherry, Taffy Armstrong, Leslie Harman, Sharon Long, Burr Williams, J.D. Drissell, R.L. Orth, and Sean Patty.
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This huge hillock (15 feet tall and 35 feet across) is one shinoak plant. In the foreground is a Sanddune Yucca (Yucca campestris.) Some of the roots of the shinoak are exposed to the left of the yucca.
In some years shinoaks produce a bumper crop of acorns and provide an amazing amount of food for the mammals of the dunes. The one acorn left in its cap proved to be emptied by an insect when it was examined.
Shinoaks add a lot of organic material to the dunes. In this photograph drifts of the leaves of the previous year fill the hollows in the slopes of a dune. The larger shinoaks have trunks as big around as an adult human's leg.
Shinoak begins to bloom in early April. Some plants unfurl their leaves at the same time while others do not. Shinoak is wind pollinated.
The catkins are usually about an inch long.
Not all branches leaf out or sport blooms in the early spring. This might be the result of poor winter moisture.
One twig leafed out, another has a few small catkins beginning to form and no leaves. Is this an indication of even less moisture available for this plant? Do different twigs have different amounts of the fungi, and could this be an explanation for the varying rates of development?
When shinoak leaves are just emerging, ranchers pull their cows out of shinoak pastures - the new leaves can make the cattle sick.
By mid-April the catkins begin to fall. The wind blows them on the surface of the sand until they collect against other vegetation.
The spring winds sometimes cover up the acorns from the previous years, and sometimes, the wind reveals acorns and acorn caps from previous years.
The leaves of grasses add to the organic litter on the sand, along with dead twigs of the oaks.
Some of the bloom buds have an intense color - is this an indication that more organic material is available for nutrients for this plant?
The shinoaks and a sand rabbitbrush have become totally green, but the big bluestems are still red. New green grass leaves will not start appearing until late April.
The nest of a bird - possibly a Lark Sparrow - is revealed before the leaves unfurl - but last year the nest was well hidden.
The rodents of the dunes keep checking out the acorns littering the sand's surface.
When the wind blows over 20 miles an hour, the under side of the leaves reveal their grayer pubescence.
Sometimes the shinoaks have a tree form. Does the shifting sand play a role in shaping the oaks? Was this oak originally buried and then the sand blown away? Notice the broken root on the right side near the base, and another root plunging into the sand on its left side.
Mesquites are found scattered through the dunes.
Sometimes the mesquites are trees, not bushes.
When the sand blows away from a mesquite, they too can survive having part of their root exposed. The original ground surface was approximately at the location of the lowest branch. The exposed roots die and are broken off by passing animals.
Javelinas have lived in the dunes for a number of years, harvesting the acorns, but roam into areas with more mesquite, as well.
Feral hogs have increased in the dunes in the last twenty years. Early settlers brought hogs to the dunes, and a folk tale relates that a train loaded with Russian boar wrecked by sand across the tracks in the early 1900s. Feral hogs are the most dangerous animals in the dunes. A 400-pound sow will attack a human between her and her piglets. Some ranchers in the dunes sell feral hog hunting leases.
One of the photographers was struck by the pattern of the feral hog droppings - a stick figure of a human.
Another photographer at first thought these feral hog droppings were vertebra of a large animal.
Some of the biggest deer found in the state of Texas are found in the dunes.
Deer tracks are much easier to find than the deer themselves.
As are deer droppings!
Was this wet soil the result of a deer urinating? Did more than one animal urinate here?
The fracture lines to the left of this deep print, and the two drag marks towards the top led the photographer to believe that a deer was moving quickly across the dunes (along with other tracks spaced far apart.)
Tiny four-footed tracks seperated by a few inches puzzled the staff of the Sibley Center. Could this possibly be the tracks of a tiny pocket mouse? Kangaroo rats have long hind feet.
Another rodent paused in its wanderings and dug a pit, but nothing was left behind to indicate what was extracted from the soil. The tracks again appeared to be something other than kangaroo rat.
Tiny paired tracks with dual half-moon shapes are also a mystery.
What animal would have hair on the soles of its feet and leave this type of track? Another mystery.
Kangaroo rats usually have lines where their tails dragged in the sand.
The lower jaw of one of the rodents of the dunes lay exposed early one morning. Other rodents will gnaw on the bones for calcium eventually.
Most of the rodents of the dunes do not urinate copiously. A kangaroo rat trail is just above the urine mark, but they never urinate copiously. None of the other tracks gave a hint at what might have passed by, but our best guess was fox (and possibly a kit fox, which are known to be in the dunes.)
A kangaroo rat had worked the previous night enlarging its hole, judging by the fresh turned dirt, and the tail track.
Was this the track of a fox dragging its tail?
A cottontail rabbit paused and left three pellets before moving on.
Why did this urine mark have a circular area where no moisture stained the soil?
Urine, as it dries, is sticky, and holds the sand grains together for a short time. Was this mark the result of two animals marking the spot - notice the two different thicknesses and colors. Again - why is there a circular area unstained and unstuck?
Coyote scat full of mesquite beans were found far from the nearest mesquite. A wolf spider hole is in the upper right corner.
This bone had been gnawed and sandblasted so long that its original shape was lost.
Did a rodent die of disease and no scavenger come to tear its vertebra apart?
For some reason, one or more kangaroo rats used the same trail many times in one night.
A perfect set of tracks of the hindfeet of a kangaroo rat impressed one of the photographers.
Kangaroo rats will close up their dens for several reasons - for warmth, for moisture retention, or to protect young.
One rodent dug the hole, and another species stuff the hole full of grasses. Why? Was the new resident a cotton rat or packrat that hauls sticks to its nest?
Several photographers noticed crusts on the ground that did not seem to be urine related.
Most of the crusty soil was near a shinoak. Is this evidence of the work of the mycorrhizial fungi on the roots of the shinoaks. Is there a chemical process that somehow glues the sand grains together?
This crusty soil had tiny roots sticking out of it. Is this evidence to prove the fungal theory?
Under a number of shinoaks, an observer can find layers of the crusty soil. Do the different layers represent different time periods? Are the deepest layers formed when the shinoak pedestal is not very tall, and are new layers formed as the dune pedestal grows in height? Some huge shinoak pedestals will have three to five feet of a "cliff face" of the layers exposed by wind erosion. Why doesn't the wind erosion cut deeper? At what rate is the "cliff face" eroded?
Not all soil crusts were naturally occurring. This crust stunk of hydrocarbons, evidence of oil field contamination. It appears that some insect did not mind the hydrocarbons, judging by all of the small holes.
The blowing sand slowly abrades wood on the soil surface.
Wandering around in the sand dunes a person always becomes enamored with the stark beauty present.
Even the roots of a shinoak on the bottom of a blowout can become an artistic design.
Why did this dune face suddenly give way? This photograph reveals the slumpage as it happens. Notice the upper two "waves" all fuzzy with dust and the crisp lines at the base of the sand slipping downslope. This is another amazing J.D. and Barbara Drissell photograph.
When it rains, the raindrops form tiny pits in the sand's surface.
The sweep of the sanddunes catches rainfall in different amounts. Notice the subtle shadings on the dunes, revealing the different amounts of moisture caught by the sand.
Why was there just one white streak where no rain had darkened the dune?
All of the photographers were entranced by the patterns in the sand left by twigs, tips of grass leaves, and other objects blowing in the wind.
Even a big grass stalk will move in a high wind.
When the wind stops blowing, incredibly delicate patterns are left. Why did one part of the dune have a series of tiny ledges between open areas where no pattern was left?
Giant sandreed's leaves turn magenta, and create an incredible woof to the tapestry of the scene. The sanddunes reveal so much delicate beauty! It is easy for a person to be hooked on coming to the dunes just to drink in the aesthetic glory.
More delicate beauty is found in the tracings of dead seedstalks of sunflowers against wispy clouds.