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”.Graham, Gary L. 1992. Texas Wildlife Viewing Guide. Falcon Press Publishing Co.. Inc. Helena and Billings, Montana. 160 pp. (page 132)Kutac, Edward A. 1989, Birders’ Guide to Texas. Gulf Publishing Company. Houston, Texas. xxii, 194 pp. (pages 208-212) 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.Judd, Frank W. 2002. Tamaulipan Biotic Province. Pages 38-58. In John W. Tunnell, Jr. and Frank W. Judd. editors. The Laguna Madre of Texas and Tamaulipas. Texas A&M University Press, College Station, Texas. xxi, 346 pp. 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. Stoleson, S. H., R. S. Felger, G. Ceballos, C. Raish, M. F. Wilson, A. Búrquez. 2005. Recent History of Natural Resource Use and Population Growth in Northern Mexico. Pages 52-86. In Jean-Luc E. Cartron, Gerardo, Ceballos, Richard Stephen Felger. Biodiversity, Ecosystems, and Conservation in Northern Mexico. Oxford University Press. New York. xvi, 1-496 pp.

The wildlife refuge was established in 1943 to protect one of the last remnants of subtropical Rio Grande riparian forest and migratory birds.MacWhorter, William. 1995. Explore Santa Ana National Wildlife Refuge: A Biodiversity Haven. Handbook of Texas. Texas State Historical Association. (accessed June 21, 2025) In a unique location in the US, where diverse climates and habitats of south Texas merge (tropical, temperate, thorn forest, wetlands, Gulf Coastal grasslands), it has a reputation for diverse birding. In addition to birding, the refuge offers opportunities for nature photography, hiking (with over 12 miles of trails), and biking (on paved roads only) and nature tram rides (seasonal), with an observation tower, a canopy bridge, as well as a visitors’ center with nature and wildlife exhibits, an auditorium, nature shop, and restrooms.U. S. Fish & Wildlife Service, Santa Ana National Wildlife Refuge. Visit Us. (accessed June 20, 2025)

The refuge is located within the Tamaulipan Biotic Province (Tamaulipan mezquital), 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 (sloughs and oxbow lakes formed by old channels of the river), 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.Lemos-Espinal, Julio A. (Editor). 2015, Amphibians and Reptiles of the US‒Mexico Border States. Texas A&M University Press. College Statioin, Texas. x, 614 pp. (see page 109)Torres, Leslie. Updated 2025. University of Texas Rio Grande Valley, Special Collections & Archives: Santa Ana National Wildlife Refuge. (accessed June 21, 2025)

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 (1747-1755), 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.Lovett, Bobbie L., Juan L. González, Roseann Bacha-Garza, and Russell K. Skowronek (editors). 2014. Native American Peoples of South Texas. The University of Texas – Pan American. Edinburg, Texas. vii, 101 pp. García, Clotilde P. 1952 (updated 1995). José de Escandón: The Father of the Lower Rio Grande Valley. Handbook of Texas. Texas Historical Association. (accessed June 23, 2025)

The majority of land now occupied by Santa Ana National Wildlife Refuge was part of the Santa Ana land grant, two square leagues (15,255 acers) 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 (Inside Ranch), 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 (Old Cemetery), 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.Frances Isbell. 2005. Santa Anan Wildlife Refuge Cemetery. Cemeteries of Texas, with permission of Hidalgo County Historical Commission.

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 (above-ground vault), or tomb, once held the remains of Cristobal Leal (1833–1876) 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 (1910–1920), 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 (1836–1846), the annexation of Texas by the United States (1845), the Mexican–American War (1846–1848), and the Treaty of Guadalupe Hidalgo (1848) 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 (4,428 acres) 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 (1848–1855). 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 (author of A Field guide to Birds of Mexico and Central AmericaDavis, L. Irby. 1972. A Field Guide to the Birds of Mexico and Central America. University of Texas Press. Austin, Texas. 264 pp. ) 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.Baker, Andrew C. 2016. Review of the book Border Sanctuary: The Conservation Legacy of the Santa Ana Land Grant, by M. J. Morgan. Southwestern Historical Quarterly 120 (1), 124-125.

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 (Ulmus crassifolia) and Anacua (Ehretia anacua). Other relatively importance species occurring in the tree layer included Sugar Hackberry (Celtis laevigata), Texas Persimmon (Diospyros texana), Narrowleaf Willow (Salix exigua), Desert Hackberry (Celtis ehrenbergiana), False Willow (Baccharis neglecta), Correhuela vine (Nephroia diversifolia), Spanish Moss (Tillandsia usneoides), Saffron Plum (Sideroxylon celastrinum). The dominant shrubs in the mid layer were Desert Hackberry (Celtis ehrenbergiana) and Lime Prickly Ash (Zanthoxylum fagara). In the ground cover, dominants species were fragrant mistflower (Chromolaena odorata), correhuela vine (Nephroia diversifolia) and the invasive Guinea grass (Megathyrsus maximus) which is displacing native species in the region.Lonard, Rober I. and Frank W. Judd. 2002. Riparian Vegetation of the Lower Rio Grande. The Southwestern Naturalist. 47(3); 420-432.

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 (Acanthocereus tetragonus) and Schott’s dog cholla (Grusonia schotti), christmas cholla (Cylindropuntia leptocaulis), Texas prickly pear (Opuntia engelmannii var. lindheimeri), lady finger cactus (Echinocereus pentalophus), Berlandier’s hedgehog cactus (Echinocereus berlandieri), dahlia cactus (Echinocereus poselgeri), strawberry pitaya (Echinocereus enneacanthus var. brevispinus), junior Tom Thumb cactus (Pelecyphora emskoetteriana), root cactus (Sclerocactus scheeri), twisted rib cactus (Thelocactus setispinus), horse-crippler cactus (Homalocephala texensis), Lower Rio Grande Valley barrel cactus (Ferocactus hamatacanthus var. sinuatus), Heyder’s pincushion cactus (Mammillaria heyderi var. heyderi), hair-covered cactus (Mammillaria prolifera var. texana), pale mammillaria (Mammillaria sphaerica). Loflin, Brian and Shirley Loflin. 2009. Texas Cacti. Texas A&M University Press. College Station, Texas. xv, 291 pp.

Fauna State of Texas: threatened species *, endangered species ** Texas Parks and Wildlife (2025). Federal and State Listed Species in Texas. (accessed June 12, 2025)

Mammals