age to over 320 million years ago, when this area was covered by an inland sea. The pluton was eventually exposed through weathering to form the rock formations visible today, which jut from the desert floor. The tanks were once capable of containing a year's supply of water. In addition to the tanks, there are several permanent springs and seasonal springs in the area. The area receives less than of rainfall a year. The syenite rock formation is covered with 'desert patina' (visible in the image below), the result of thousands of years of weathering of the rock surface by sun, sand, and water; the site is culturally and spiritually significant to many Native Americans, such as the Mescalero Apache, the Kiowa, the Hopi, and the Pueblo people. This significance is partially manifested in the pictographs (rock paintings) that can be found throughout the region, some of which are thousands of years old. Hueco Tanks contains the single largest concentration of mask paintings by Native Americans in North America, of which hundreds exist at this site. Wildlife Freshwater shrimp and spadefoot toads survive at the site; for this and other reasons, visitors are cautioned against touching the pools of water at Hueco Tanks to avoid destroying the eggs of these animals. Other amphibians seen in the park include barred tiger salamanders. Around 30 different species of reptiles live in the area. In 2002, 222 different species of bird were documented at the site during the year. Migratory birds such as waterfowl and songbirds pass through during migration seasons. Several birds such as the prairie falcon, burrowing owl, white throated swift, black-chinned hummingbird, ash throated flycatcher, Crissal thrasher, blue grosbeak, Scott's oriole and lesser goldfinch all likely breed in the area. The park is home today to mule deer, black bears, bobcats, gray fox, coyotes, badgers, ringtails, skunks, raccoons, mountain lions, black-tailed jackrabbits, desert cottontail, eastern cottontail, six species of bats and twenty species of rodents. Plants Around the syenite outcrops, the park is surrounded by Chihuahuan Desert scrub with creosote bush as the dominant species. The site contains enough water to support live oaks and junipers, species which survive from the last ice age. Other trees found in the area include netleaf hackberry, Texas mulberry, Mexican buckeye, catclaw acacia, and Arizona white oak. Hueco Tanks has the only population in the United States of the plant Colubrina stricta. Rock climbing