Santa Ana National Wildlife Refuge
Santa Ana National Wildlife Refuge is a National Wildlife Refuge situated along the banks of the Rio Grande, south of Alamo in the Lower Rio Grande Valley, in Hidalgo County, Texas. This sub-tropical sanctuary harbors one of the highest wildlife diversities of any single unit in the National Wildlife Refuge system and has been referred to as the “Gem of the National Wildlife Refuge System”. Many Mexican and tropical species reach the northern limit of their distributions in the Lower Rio Grande Valley, including several that occur nowhere else in the US. Santa Ana National Wildlife Refuge preserves one of the largest tracks of old growth habitat in the Lower Rio Grande, in a region where much of the land use has been dominated by, and shifted over the last century, from small farms, to commercial agro-industries, to significant population growth and urban development in recent decades.
The wildlife refuge was established in 1943 to protect one of the last remnants of subtropical Rio Grande riparian forest and migratory birds. In a unique location in the US, where diverse climates and habitats of south Texas merge, it has a reputation for diverse birding. In addition to birding, the refuge offers opportunities for nature photography, hiking, and biking and nature tram rides, with an observation tower, a canopy bridge, as well as a visitors’ center with nature and wildlife exhibits, an auditorium, nature shop, and restrooms.
The refuge is located within the Tamaulipan Biotic Province, a xeric region with thorn scrub vegetation. However, contrasting with much of the semi-arid ecosystems of the region, the refuge is situated in the riparian zone of the Rio Grande protecting resacas, mudflats, bottomland forest, riparian terraces, and some areas of upland thorn forest. The topography is relatively flat, with small hills and terraces descending to the river. Elevations in the refuge range from 22 to 34 meters. The refuge is largely bordered by agriculture and croplands to the north, east, and west, and the Rio Grande forms the southern boundary. The geology of the area consists of a Cretaceous base, covered by Cenozoic sedimentary marine depositions of limestone, sandstone, siltstone, claystone, topped with deep Quaternary alluvial soils of sand, clay, and loam.
Due to its location near the Mexico–United States border, the refuge was at risk of environmental damage during the construction of the Mexico–United States border wall. The administration exempted the construction in the refuge, but built on the border of it, leading to possible interference due to noise.
History
Archeological records show that various groups of nomadic Native Americans, collectively referred to as the Coahuiltecans by anthropologists, roamed the Lower Rio Grande Valley for at least 11,000 years. After the Spanish made concerted efforts to colonize the Lower Rio Grande Valley, epidemics such as smallpox, conflicts with the Spanish, Apache, and other indigenous groups, high infant mortalities, and assimilation the Coahuiltecans as a discrete cultural entity had all but vanished in less than a century. Following Mexico’s independence from Spain in 1821, land grants were given to stimulate development in the region, and after the Republic of Texas declared independence in 1836, to bolster Mexico’s claim within the disputed boundary lines as well.The majority of land now occupied by Santa Ana National Wildlife Refuge was part of the Santa Ana land grant, two square leagues awarded to Benigno Leal by the state of Tamaulipas, Mexico on May 19, 1834, when Texas was still Mexican territory. Leal established the Rancho del Adentro, constructed a house and ranch headquarters, and started a cemetery on the property. Although the house and any remnants of the ranch are no longer evident, the Santa Ana Cemetery, or Cementerio Viejo, is still there today. It includes a tomb constructed of handmade bricks and about 30 graves dating from the 19th and early 20th centuries. Portions of the cemetery’s fence erected ca. 1875 and made of hand cut Texas ebony still stand. The cemetery is maintained by the refuge and open to visitors.
Among those interned in the Cemetery are members of the Leal family and others from the ranch and neighboring area. Based on family accounts, Benigno Leal was killed by Indians in retribution for an Indian Leal had killed trespassing on his property. Factions of the Lipan Apache had been pushed south into the region after their conflicts with the Comanches in the 1720s, and fights with the Apache and raiding Comanche in the Lower Rio Grande Valley were known to occur in the mid-19th century. The boveda, or tomb, once held the remains of Cristobal Leal and wife his María Rafaela Treviño. Cristobal was the son of Benigno Leal and his wife Victoria Balli, who they adopted in 1859. Sometime during the Mexican Revolution, about 1915–16, the tomb was violated and looted, and the bones were dispersed by bandits making border rides. It was restored after the refuge was established.
Following disputes over the international boundary between Mexico and the Republic of Texas, the annexation of Texas by the United States, the Mexican–American War, and the Treaty of Guadalupe Hidalgo establishing the Rio Grande as the international border, Cristobal and his wife Victoria Balli Leal began selling their property north of the river in parcels. Dr. Eli T. Merriman, a Mexican-American war veteran, Union surgeon, and one of the first commissioners of Hidalgo County, acquired the east league in 1852 for ranching. In 1853, Thomas Walter Jones of Washington DC was buried on Merriman’s ranch after he drowned in the Rio Grande in the vicinity of the ranch while conducting surveys with United States and Mexican Boundary Survey. Dr. W. T.G. Brewster, also a Union surgeon during the American Civil War, acquired the east league from Dr. Merriman in 1878. And finally Peter Ebenezer Blalock, a co-developer of Alamo, was the owner of all the land in the original Santa Ana Grant by 1902. Concerns over the rapidly vanishing natural habitat in the valley due to agriculture began as early as the 1930s. Organizations such as the Rio Grande Valley Nature Club and individuals like Irby and Anna May Davis petitioned the U.S. Biological Survey to preserve some of the last remaining riparian forest. The land for the refuge was purchased by the federal government in 1943 for $22,414.
Flora
In the Lower Rio Grande Valley, 99% of the riparian vegetation adjacent to the Rio Grande has been eliminated. Among seven study sites in the region retaining natural vegetation, species richness was greatest at the Sabal Palm Sanctuary and Santa Ana National Wildlife Refuge. At Santa Ana, the dominant tree species in the canopy layer were Cedar Elm and Anacua. Other relatively importance species occurring in the tree layer included Sugar Hackberry, Texas Persimmon, Narrowleaf Willow, Desert Hackberry, False Willow, Correhuela vine, Spanish Moss, Saffron Plum. The dominant shrubs in the mid layer were Desert Hackberry and Lime Prickly Ash. In the ground cover, dominants species were fragrant mistflower, correhuela vine and the invasive Guinea grass which is displacing native species in the region.Cacti
South Texas has a wealth of cactus species, several of which are predominantly Mexican species that grow nowhere else in the US. Species recorded in Hidalgo County include the night blooming tringle cactus and Schott’s dog cholla, christmas cholla, Texas prickly pear, lady finger cactus, Berlandier’s hedgehog cactus, dahlia cactus, strawberry pitaya, junior Tom Thumb cactus, root cactus, twisted rib cactus, horse-crippler cactus, Lower Rio Grande Valley barrel cactus, Heyder’s pincushion cactus, hair-covered cactus, pale mammillaria.Fauna
State of Texas: threatened species *, endangered species '''**'''Mammals
A few of the mammals known from Hidalgo County include the nine-banded armadillo, Virginia opossum, raccoon, black-tailed jackrabbit, Rio Grande ground squirrel, northern grasshopper mouse, Gulf Coast kangaroo rat, collared peccary, bobcat, and coyote.Historically, several large carnivores occurred in the region as well, such as jaguars **, gray wolves **, and American black bears *, all now extirpated. Hidalgo County was one of the last strongholds of jaguarundi ** and ocelot ** populations in Texas. Zoologist David Schmidly wrote in 1994 “The rarest of all native cats, jaguarundi are now thought to be represented in the lower Rio Grande Valley by no more than 15 individuals”, and its survival was described as “doubtful”. As of 2025 its status in the US is somewhat unclear. Some have speculated it has been extirpated, and Texas Parks and Wildlife states Jaguarundis are extinct in Texas. The US Fish & Wildlife Service states the ocelot and jaguarundi are “known to still prowl the deep forest” in Santa Ana National Wildlife Refuge. Small populations of ocelots persist in Laguna Atascosa National Wildlife Refuge and neighboring Texas counties to the east. Although there are several confirmed records of white-nosed coati * from the Lower Rio Grande Valley, they are believed to represent wandering, solitary males following riparian corridors from the south, and released or escaped pets. It is unlikely that south Texas ever supported a breading population, and they are likely extirpated from the region now.
Birds
Documented within the refuge's borders are 397 bird species, many of which are migratory species on their way to and from Central and South America. Some of the waterfowl and waders to be found there are black-bellied whistling-duck, fulvous whistling-duck, mottled duck, least grebe, anhinga, tricolored heron, white ibis, wood stork *, and least tern.Among the birds of prey found in the refuge are Harris' hawk, white-tailed kite, and peregrine falcon *. Hook-billed kite and grey hawk * are seen occasionally in the refuge and attract birders from around the world. Other species recorded in the refuge include plain chachalacas, white-tipped dove, groove-billed ani, ferruginous pygmy owl *, common pauraque, buff-bellied hummingbird, green kingfisher, ringed kingfisher, golden-fronted woodpecker.
Passeriformes species include Northern Beardless-Tyrannulet *, Tropical Kingbird, Great Kiskadee, green jay,, Clay-colored Robin, Altamira oriole, Hooded oriole, and Olive sparrow. More than 35 species of New World warblers have been seen, including the golden-winged warbler, magnolia warbler, Northern parula, tropical parula *, American redstart, palm warbler, and yellow-breasted chat.
Reptiles
The area is rich in reptile diversity. The Texas tortoise * is well adapted to the semiarid environment of the region, while the distribution of the Rio Grande cooter is restricted to the Rio Grande and some of its tributaries. Some of the lizards documented from Hidalgo County include the reticulate collared lizard, Texas banded gecko, blue spiny lizard, graphic spiny lizard, northern rosebelly lizard, ornate tree lizard, four-lined skink, and the parthenogenic Laredo striped whiptail.Venomous snakes include the western diamond-back rattlesnake, the Texas coralsnake, and the rare desert massasauga. A few other species recorded from Hidalgo County are the glossy snake, regal black-striped snake *, Central American indigo snake, speckled racer *, Tamaulipan hook-nose snake, Mexican hog-nose snake, Chihuahuan nightsnake, Mexican milksnake, northern cat-eyed snake *, Schott’s whipsnake, gopher snake, long-nose snake, and the eastern patch-nose snake among several others.
Amphibians
Salamanders recorded in Hidalgo County include the western lesser siren and the black-spotted newt *. Although the cane toad is an invasive species in many regions around the world, it is native to South Texas, as are other tropical species recorded in Hidalgo County, such as the white-lipped frog *, Rio Grande chirping frog, Mexican treefrog *, and the sheep frog *.Butterflies
Santa Ana is home to almost half of all butterfly species found in the United States. More than 300 species of butterflies have been observed at the refuge, with as many as 65 having been seen on a single day.References