Just such a change of channels apparently created the bench of bottomland where Rio Grande Village lies today. People have been camping here for thousands of years, as shown by the many deep mortar holes where meal was ground in the limestone ledges near the pumping station. Certainly the place had much to recommend it: wood and water, abundant game, rich soils, an agreeable winter climate, and beautiful views of river and mountains. After the white man came to stay in the early 1900s most of the native flora changed. Farmers cleared the bottomland to plant cotton and grains, cut down the lanceleaf cottonwoods for roofbeams, dredged ponds and ditches, and enclosed springs. Nowadays, the plants you see are often exotics brought in from outside to create shade and lawns.
Such are the eastern cottonwoods with their heart-shaped leaves, the evergreen live oaks and smooth sycamores, the sweet-smelling honey locust and eucalyptus trees, and that fine green carpet of Bermuda grass. Like the farmers’ field crops, these interlopers cannot flourish without irrigation and sometimes even that is not enough. Dozens of eastern cottonwoods have died in recent years.
A good place to see native plants and animals is along the Rio Grande Village Nature Trail, which starts at the campground and leads to a hill above the river. A walk along this trail is doubly interesting because it shows greenbelt and shrub desert side by side, the two habitats often separated by less than a vertical or horizontal meter. The jungle starts at the edge of the clearing and almost at once you come upon a warm spring run. This may be where the rare little Big Bend mosquitofish, Gambusia gaigei, originated, but all you see today is a larger relative, Gambusia affinis. These five-centimeter (two-inch) predators, little as they are, soon take over. They apparently are invaders from the Rio Grande.
In wet weather this whole spring area becomes a swamp and even in dry times moisture-loving plants crowd the trail. You pick your way beneath black willow trees and grapevines festooned with wild grapes, stop to admire the yellow tube-flowers on the tree tobacco, stoop to avoid a spear slanting from the solid wall of common and giant cane. These two tall woody grasses stand 4.5 meters (15 feet) high and put out great, plume-like flowering heads that shine silver in the sun. Indians used the stems for arrow shafts and ate the roots raw, roasted, or boiled. Many an early settler roofed and even walled his house with cane. Today the reeds supply deer and cattle with attractive browse, and the thickets serve both as home and hunting ground for birds, small mammals, and reptiles.
Here is the cleverly constructed nest of a gray wood rat. And there, crouched beneath a bush like some storybook monster is an enormous spiny lizard. Rosy and gray, he peers back unblinking, still as a stone, then melts away so quickly he is gone before you see him move.
A little further on the trail climbs a short rise, topping out on Chihuahuan Desert complete with creosotebush, dog cholla, ocotillo, and the standard collection of cactuses. If you take the trail in spring or summer, the mound-building strawberry cactus will be covered with hot pink blossoms and delicious fruit. By fall the fiercely barbed blades of the false-agave, or hechtia, will have taken on a reddish tinge. In wintertime the tasajillo cactus will be dressed like a tiny Christmas tree in long green spines and bright red fruits. But at any season this water-starved scene stands in sharp contrast to the marsh, rank with reeds and bulrushes, that lies just below.
Unlikely as it may seem you are looking at a beaver pond backed up behind an actual beaver dam hidden in the reeds. The wary, nocturnal beaver is seldom seen and you will look in vain for the familiar beaver lodge, because Big Bend beavers make do with what the floodplain has to offer. Instead of building wooden houses, these rodents dig burrows in the river bank, foraying from there to feed on willow, cottonwood, seepwillow, and river cane. Around the turn of the century the Rio Grande and its main tributaries abounded with beaver, but fur traders trapped them to the brink of extinction, woodcutters and farmers destroyed their food supply, and cattle feeding in the canebrakes trampled their burrows.
It is hard to imagine just what destroying the trees and ground cover can do to fertile land and to a living stream, but a visit to Terlingua Abaja shows you. James B. Gillett, foreman of the famous G-4 Ranch, recalled that in 1885 “the Terlingua was a bold running stream, studded with cottonwood timber and was alive with beaver.” There was one grove of trees where he had seen at least 1,000 head of cattle enjoying the shade. But after the Terlingua mines opened, Mexican farmers established a community at Terlingua Abaja, a few kilometers up the creek from its junction with the Rio Grande. All the cottonwoods up and down the creek fell to construction and hungry mine furnaces and the virgin earth turned bottom up beneath the plow and grubbing hoe. Today this once fertile valley is a wasteland.
The Rare Big Bend Mosquitofish
The Big Bend mosquitofish (Gambusia gaigei) has a miniscule geographic range. Not only is it restricted to the park, as some other species are, but it is also restricted to one pond. The fish was first identified in 1928 in Boquillas Spring. Unfortunately, the spring soon dried up and for some 20 years the fish was thought extinct. In 1954 more were found near Rio Grande Village. This group was later threatened, and a pond was built especially for the fish. But people dumped into the pond other fish that ate this tiny mosquitofish. At one point the world’s only survivors were two males and a female, Rio Grande Villagers that biologists had removed to a laboratory aquarium at the University of Texas at Austin. A cold winter again killed nearly the whole park population, and again the Austin-raised stock replenished it. Gambusia gaigei gives birth to live offspring and has been around as a species since mastodons. They feed largely on mosquito larvae.