With less than 12 inches of rain per year and high temperatures in the 100s, survival in Saguaro National Park, which is part of Arizona's Sonoran Desert, requires special adaptations to heat and drought.
The saguaro cactus, for example, has a long network of roots that grow close to the surface and soak up moisture during brief, infrequent showers. Water is stored in the saguaro's gelatinous tissue which, when fully expanded, can hold as much as 200 gallons. Thick, waxy skin minimizes evaporation, as does the absence of leaves. The plant's notorious spines repel thirsty animals, provide shade, trap cool air, and protect it from drying winds.
Many animals avoid the intense heat by hunting or gathering food only at night or, like the roadrunner and Gila monster, during the cool hours of dawn and dusk. Birds such as the Gila woodpecker and gilded flicker make holes in the saguaro itself, using the burrows as protection against both searing heat and biting winter cold. When the original occupants move out of the holes, any of several other bird species move in, including cactus wrens, American kestrels, screech owls, and western kingbirds.
The jackrabbit employs quite a different method to stay cool. It uses its prominent ears as radiators, ridding itself of excess heat directly through the skin. Perhaps the most intriguing adaptation is that of the kangaroo rat, which is able to survive a drought by drawing all the water it requires from seeds.
Humans have also learned to survive in the Sonoran's harsh climate. Native Tohono O'odham Indians -- descendants of the ancient Hohokam Indians whose archaeological remains are scattered throughout the desert -- still harvest the succulent fruit of the saguaro for a variety of foods such as jam, syrup, and ceremonial wine. They also use the seeds of the saguaro and, after the cactus dies, the strong woody skeleton that holds it erect.
Saguaro National Park Climate and Life Zones
First-time visitors often expect the desert to be unrelentingly hot. But the weather at Saguaro National Park is actually quite variable. While daytime temperatures in summer regularly soar above 100 degrees, nights can be as much as 20 degrees cooler.
Temperatures sink well below freezing in winter, and snow is not uncommon, especially at the higher elevations. Perhaps the best time to visit is from October to April, when daytime temperatures hover around the 60s and 70s.
Climate varies significantly by elevation, too, tending to become cooler and wetter the higher one climbs. By hiking up the Rincon Mountains, for example, one passes through several distinct plant communities, rising from the low desert scrub inhabited by the saguaro forest to the mid-range oak and pine woodland. At the highest elevations, there are stands of ponderosa pine and Douglas fir that are similar to the forests of the northern United States.
Life in the Arizona desert is quite different than the one you lead, but that's what makes it interesting to study. Visit Saguaro National Park and get a great introduction to how plants and animals not only adapt to this habitat but grow and thrive.
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