NATURAL AND SCIENCE
The nearly 800,000 acres of Joshua Tree National Park were set aside to protect the unique assembly of natural resources brought together by the junction of three of California’s ecosystems. The Colorado Desert, a western extension of the vast Sonoran Desert, occupies the southern and eastern parts of the park. It is characterized by stands of spike-like ocotillo plants and “jumping” cholla cactus.
The southern boundary of the Mojave Desert reaches across the northern part of the park. It is the habitat of the park’s namesake: the Joshua tree. Extensive stands of this peculiar looking plant are found in the western half of the park.
A third ecosystem is located in the western most part of the park above 4000 feet. The Little San Bernardino Mountains provide habitat for a community of California juniper and pinyon pine.
The plant diversity of these three ecosystems is matched by the animal diversity, including healthy herds of desert bighorn and six species of rattlesnakes. Joshua Tree National Park lies astride the Pacific flyway of migratory birds, and is a rest stop for many. It was for this unusual diversity of plants and animals that Joshua Tree National Monument was set aside on August 10, 1936.
The park also encompasses some of the most interesting geologic features found in California’s desert areas. Exposed granite monoliths and rugged canyons testify to the tectonic and erosional forces that shaped this land. Washes, playas, alluvial fans, bajadas, desert varnish, igneous and metamorphic rocks interact to form a pattern of stark beauty and ever changing complexity.
ANIMALS
The broad vistas of desert landscapes can distract the visitor’s eyes from the small and quick near at hand. Despite the impression that the desert is lifeless, many animals make their homes in deserts. Birds, lizards, and ground squirrels are most likely to be seen because they are largely active during the day. However, it is at night that desert animals come out to roam. Mostly nocturnal animals include: snakes, bighorn sheep, kangaroo rats, coyotes, and black-tailed jack rabbits. Dusk and dawn are good times for viewing many kinds of animals, both those just going to bed and those just getting up.
Animals that thrive in desert environments often have special adaptations for dealing with limited water and high summer temperatures. One does not walk far in the desert without seeing a multitude of burrow openings. The smaller mammals and all reptiles take refuge from the heat underground. Reptiles are physiologically adapted to getting along with much less water than mammals and birds can fly to water. And desert mammals make more efficient use of their bodies’ water supply than does the human body. Nevertheless, the springs and seeps in the park are necessary to the survival of many animals.
Most of the reptiles and many small rodents and insects go into an inactive state of hibernation during the winter. However, winter is the time of greatest bird concentrations in the park, because of the presence of many migrant species.
AMPHIBIANS
Frogs are probably the last thing that people expect to see when they visit the desert. However, some frogs and toads have adapted to life in arid lands. True, they still need water, but they seek it out when it is available. Amphibians are animals that have two life stages: a larval, aquatic form and an adult, terrestrial form. This is the difference between a tadpole and a toad. In Joshua Tree, we have two important amphibians. The California tree frog is found only in southern California and is listed as a Species of Special Concern. It is found in the rocky, permanent water sources created by the Pinto Fault along the northern edge of the The red-spotted toad is a true denizen of the desert, where it spends most of its life underground. Found from one end of the park to the other, it appears after good, soaking rains. This toad lays its eggs in potholes, springs, and the intermittent streams found in rocky canyons after heavy rains. Breeding and toad choruses occur in spring following winter rains or after the monsoon storms of summer. Male tree frogs and toads do the vocalizing. Gelatin-covered eggs are laid by the females at the bottom of a pool and hatch in a few days. Then, in the case of toads, it is a race to finish the tadpole stage before the pool dries up. park. This species reaches the eastern edge of its range here.
ARTHROPODS
You can find insects, spiders, and other multi-legged creatures (arthropods) anywhere in the world. So it is no surprise that there are thousands of species of arthropods in Joshua Tree National Park. They range in size from the four-inch-long tarantula (Aphonopelma iodium) and the green darner (Anax junius)—with its four-inch wingspread—to tiny gnats and mites. Joshua Tree’s arthropods include the beautiful salmon-colored fairy shrimp (Branchinecta), the five-inch giant desert scorpion (Hadrurus arizonensis), and more than 75 species of butterflies. There are even more kinds of moths than butterflies. The yucca moth (Tege All arthropods feature a hardened outer shell of exoskeleton, a segmented body, and jointed appendages. The activities of these small animals are most profoundly affected by their immediate environment: all the variations of temperature, moisture, space, and food that delimit their homes. These places
are referred to as microhabitats. Some microhabitats are decidedly different from the surrounding environment. Take for example the soft-bodied, moisture-loving larva of the cactus fly (Copestylum mexicana) living in the very humid, warm environment of rotting cactus stems while surrounded by searing desert heat and single-digit relative humidity.ticula paradoxa) is responsible for pollinating the Joshua trees after which the park is named. Several species of ants are found on the desert. Their varied adaptations are true wonders of nature. The harvester ants (Pogonomymex and Veromessor) busy themselves collecting seeds, which they store in underground granaries to use during the dry months. The honeypot ants (Myrmecocystus) have an exceptionally weird habit. Some members of the colony swallow so much honey that their abdomens get too large for them to move. They become, in effect, storage jars, providing food for the rest of the colony.