Much has changed in Idaho since the Pliocene, when the Hagerman horse, ancient camels, and mastodons, thrived in forests and on grasslands. Over 20 inches of precipitation a year created a lush environment for the development and survival of a wide variety of animals. Learn more about Hagerman's ancient past.
Today, the Hagerman area receives less than 10 inches of precipitation. However, due to the Snake River, natural springs, and other water sources, the area is still able to support an incredible diverse species population. The riparian zones of the Hagerman area support habitat that is important for migratory waterfowl and other many other species.
A Sagebrush Steppe Community
The predominant naturally-occurring vegetation on the Monument is composed of the sagebrush steppe plant communities once common to much of the intermountain region of southern Idaho. These shrub steppe communities include a dominant shrub, often sagebrush, interspersed with open, sparsely vegetated areas of grasses and forbs.
The steep slopes of the Monument’s bluffs west of the Snake River provide an environment that contributes to the diversity of plant species. In addition, a riparian zone and localized wetlands occur along the Reservoir.
Plants
The monument is home to a variety of native grasses such as: wheatgrass, bluegrass, Indian ricegrass, and Great Basin wildrye.
Flora on the upland plateau was once a vast complex of Wyoming big sagebrush (Artemisia tridentata ver. wyomingensis) association. Greasewood (Sarcobatus vermiculatus) and rabbitbrush are the dominant shrubs where the soils are more alkaline. Scattered occurrences of four-wing saltbush (Atriplex species) occur where soils contain more calcite.
Riparian vegetation includes black cottonwood (Populus trichocarpa), bulrush (Scirpus spp.), and cattails (Typha spp.). Willows (Salix spp.) are most common in the vicinity of the dam and the falls to the north and south of the Monument.
Animals
Common mammal species include mule deer, red foxes, coyotes, badgers, cottontail rabbits, and yellow-bellied marmots. River otter, beaver, muskrat, mink, and other furbearers are found in and around Hagerman’s ponds, marshes, and waterways.
A variety of wading and shorebirds nest at Hagerman, while others stop briefly before continuing their northward migration. The short-eared owl and the western screech owl commonly nest in Hagerman. The ring-necked pheasant, grey partridge, and California quail also call Hagerman home. Black-crowned night herons, great blue herons, Virginia rails, American avocets, and spotted sandpipers are some of the species that stop briefly. Ospreys, bald eagles, peregrine falcons, and rough-legged hawks are seasonal guests. Marsh wrens, rufous-sided towhees, and numerous warblers species find sanctuary within the riparian areas, while horned larks, vesper sparrows, and northern orioles feed and nest among upland and wooded habitats.
Striped whip snakes, western rattlesnakes, and gopher snakes hunt among rock-strewn boulder fields, while short-horned, western whiptail and sagebrush lizards bask in the sun. Western and Great Basin spadefoot toads inhabit the various moist areas and bullfrogs, northern leopard frogs, pacific tree frogs, and striped chorus frogs can be heard singing in the distance.
Species of fish in this stretch of the Snake River include rainbow trout (Salmo gairdneri), small-mouth bass (Micropterus dolomieui), chub (Couesius plumbeus), suckers (Catostomus spp.), and non-native carp (Cyprinus carpio). Sturgeon (Acipenser transmontanus), although once plentiful, are now rare.
Much of the Snake River and many of its reaches have been declared as critical habitat for the Snake River sockeye salmon (Oncorhynchus nerka), a federally listed endangered species, and the Snake River fall Chinook salmon (Oncorhynchus tschawytscha), a federally listed threatened species. In addition, the entire Snake River Basin has been designated as an Evolutionary Significant Unit for the West Coast steelhead (Oncorhynchus mykiss).
Habitat Loss & Invasive Species
Livestock grazing prior to establishment of the Monument in 1988 also undoubtedly contributed to alteration of soils, loss of native grasses, and establishment of non-native plant species.
Non-native plant species known to be present include Russian olive (Eleagnus angustifolia), Russian thistle (Salsola kali), quackgrass (Agropyron repens), cheat grass (Bromus tectorum), blue mustard (Chorispora tenella), tansymustard (Descurainia sophia), tumble-mustard (Sisymbrium altissimum), and medusa head (Taeniatherum caput-medusae).
These and other non-native species likely to be present, compete with the Monument's native plant communities, disrupting ecosystem processes.
