The San Luis National Wildlife Refuge encompasses over 26,800 acres of wetlands, riparian forests, native grasslands, and vernal pools. A thriving population of the endemic tule elk is showcased by one of three auto tour routes. The Refuge is host to significant assemblages of birds, mammals, reptiles, amphibians, fish, insects, and plants; some of which, such as the California tiger salamander, the long-horned fairy shrimp, and San Joaquin kit fox, are endangered species.
In 1966, the first parcel of the Refuge was purchased with Federal Duck Stamp funds to provide a sanctuary for migratory waterfowl. Over the years the Refuge has steadily grown in size and today it is comprised of six contiguous units: San Luis, East Bear Creek, West Bear Creek, Freitas, Blue Goose, and Kesterson. The San Joaquin River bisects the eastern portion of the Refuge.
The Refuge is a major wintering ground and migratory stopover point for large concentrations of waterfowl, shorebirds, and other waterbirds. Large flocks of green-winged teal, northern shoveler, mallard, gadwall, wigeon, cinnamon teal, northern pintail, ring-necked duck, canvasback, ruddy duck, and snow, Ross', and white-fronted geese swarm over the mosaic of seasonal and permanent wetlands that comprise a quarter of the Refuge. Waterfowl generally remain until late March before beginning their journey north to breeding areas. However, some mallard, gadwall, and cinnamon teal stay, breed, and raise young on the Refuge.
Shorebirds including sandpipers and plovers can be found in the tens of thousands from autumn through spring. Large flocks of dunlin, long-billed dowitchers, least sandpipers, and western sandpipers can be seen feeding in shallow seasonal wetlands, whereas flocks of long-billed curlews are found using both wetlands and grasslands. More than 25 species of shorebirds have been documented at the San Luis NWR.
The San Luis NWR has played a key role in the recovery of the tule elk, a non-migratory elk subspecies found only in California. Prior to the mid-1800s, an estimated 500,000 tule elk lived in California. Due to over-hunting and loss of natural habitat, they were driven nearly to extinction by the turn of the twentieth century – by some accounts, the population was reduced to as few as 20-30 individuals. In 1974 a herd of 18 animals was established in a large enclosure at the San Luis NWR and has since thrived.
Elk from this herd are periodically relocated to join other tule elk herds, or establish new ones, throughout California. A true wildlife recovery success story, the statewide tule elk population has recovered to more than 4,000 animals.
Less well-known are the extensive upland habitats found on the Refuge. Many of these habitats are characterized by saline and alkaline conditions in conjunction with low rainfall and an arid climate that characterize the San Joaquin Valley. These habitats support a rich botanical community of native bunchgrasses, native and exotic annual grasses, forbs, and native shrubs. Trees, such as the valley oak, cottonwood, and willow are found along riparian corridors. In these areas, visitors might encounter coyotes, desert cottontail rabbits, ground squirrels, western meadowlarks, yellow-billed magpies, and loggerhead shrikes, as well as northern harriers, white-tailed kites, and other raptors coursing over the vegetation. Stately great blue herons, great egrets, and white-faced ibis are frequently sighted throughout the Refuge.
The Refuge contains the Complex's Visitor Center and Headquarters, which features an exhibit hall with interactive educational exhibits about wildlife and habitats and a classroom for conducting environmental education fieldtrips for visiting schools. The Visitor Center is open daily.
The Refuge has three auto tour routes with associated nature trails and observation platforms from which the public can view and photograph wildlife and nature. The Refuge also allows fishing at designated sites and has a large waterfowl hunting program.