Sloan Canyon National Conservation Area encompasses a 75 square mile area of volcanic hills, an abundance of desert-dwelling plants and animals and amazing cultural resources just to the south of Anthem and Henderson. It is the area surrounding the McCullough Mountains with boundaries from roughly I-15 on the west to Railroad Pass to the east extending south to the edge of Jean Dry Lake. Approximately 17,000 acres within the NCA were designated as wilderness by Congress in a 2002 public lands bill.

Temperatures may top 105F (40.6C) for 90 to 100 consecutive days from June to October with an average of 3 inches of rain. The winter and summer pattern of rainfall in this desert stimulates the growth for plant and animal species such as creosote and bursage flats, mesquite, and an abundance of cacti, including cholla.

Sloan Wildlife

Wildlife include the big horn sheep, the endangered desert tortoise, lizards, and rattlesnakes. Every plant and animal has adapted to an environment we would find uninhabitable.

Birds have a great advantage in being able to fly to find desert water. You'll find the best birdwatching from February to May and August to November during migrations. Look for warblers, swallows, flycatchers, and phoebes along vegetation-lined washes. Red-tailed hawks soar year-round. Coveys of Gambel’s quail make the NCA their permanent home as well.

Sloan’s wildlife has developed many mechanisms to survive the desert’s heat and survive for months without rain such as burrowing, nocturnal living, and astonishing water conservation techniques The only water sources around are natural rock basins called tinajas that catch rainwater, a few artificial water areas, and flowing washes after rains. Never expect to find water available for your use.

Light-colored fur helps mammals like mountain lions reflect, not 'soak' in the heat. The scales of lizards help them deflect heat too. Perhaps most incredible are the built-in water saving abilities of many desert animals. Some of Sloan NCA’s bighorn sheep may go for weeks or months without visiting a water hole. The sheep draw some moisture from food and rainwater pooled in rocks, and can survive despite losing up to 30 percent of their body weight. When water is plentiful, the bighorns quickly recover.

Almost three-quarters of all desert animals are burrowers. Desert Tortoises become dormant in burrows during the hottest and coldest times of the year, when temperatures fluctuate only two degrees F just 18 inches below the surface. Kangaroo rats, pocket mice, ground squirrels, and snakes all find underground shelters.

Cold-blooded reptiles like hot, dry climates. Lizards and snakes dash and slither throughout the NCA. Side-blotched lizards turn up just about everywhere. Whiptail lizards brave the heat of the day in search of termites and other insects. Desert horned lizards hunt for ants in valleys and washes. These lizards can defend themselves by squirting blood from their eye sockets.

At least 15 species of snakes live here, including six kinds of rattlesnakes. Three of those rattlesnake species are common: the sidewinder, recognized at once by its sideways locomotion and "horns" above its eyes; the western diamondback rattlesnake, largest of the bunch, living primarily in the lower hills; and the Mojave Green rattlesnake possesses the most toxic venom of our rattlesnakes and rarely rattles, even when disturbed.

Snakes would rather leave you alone, if you leave them alone. They play an important role as predators in the desert community. Before heading into the desert, pick up information on snake bite prevention from the BLM office.

Geology

The present day serenity of Sloan Canyon National Conservation Area contrasts to its violent volcanic past. Sloan Canyon contains one of the best records of volcanic activity in the Las Vegas area and contains at least eight volcanoes that erupted from time to time millions of years ago. Volcanoes that have not erupted for a while, but which may erupt again, are considered dormant. Volcanoes that have not erupted for thousands of years are called extinct. All the volcanoes at Sloan Canyon are extinct.

For more information read Volcanoes of the McCullough Range, Southern Nevada by Eugene Smith, Denise Honn and Racheal Johnsen, Department of Geoscience, UNLV.

From the paper:

The McCullough Range preserves a unique record of Miocene volcanism in the western Lake Mead area of Nevada. The basal part of the volcanic section is composed of interbedded basalt and dacite of the McClanahan Spring, Cactus Hill, and McCullough Wash volcanoes (Eldorado Valley volcanic section), and the Colony volcano, which is age-equivalent to, but does not crop out within, the Eldorado Valley volcanic section (18.5–15.2 Ma).