Gary Archibald, Weathercaster

Climate and the animal world (including human beings, of course) have multifaceted dynamic relationships. In my last installment I discussed the harsh, wind-driven, extreme cold of the Arctic climate and its effects on the wildlife that inhabit such geographic locales. I focused on polar bears, the resilient although endangered kings of the North. Mother Nature has designed a perfect creature capable of surviving sub-zero temperatures that are lethal to the vast majority of animals who inhabit the Earth, including humans. The thick fur, weighty body fat and highly tuned respiratory system enable the polar bear to withstand the frigid elements.

In contrast, desert climates – hot, arid, water-deprived – are unique habitats for another group of Mother Nature’s specialists – those creatures able to withstand extreme heat capable – deadly and unforgiving likewise.

Ectotherms, such as snakes (specific species that are found in desert climates), are specially equipped to handle such conditions. Ectothermy refers to creatures that control body temperature through external means – thermoregulation - (Greek: "ectos"εκτος = "outside," "thermos" θερμος = "warm"), such as the sun, or flowing air/water. ECTOTHERMS or so-called “cold-blooded” creatures take on the temperature of their surroundings.

The term is now outdated in scientific contexts. Cold-blooded creatures were, initially, presumed to be incapable of maintaining their body temperatures at all. They were presumed to be "slaves" to their environments. Whatever the environmental temperature was, so too was their body temperature. They are hot when their environment is hot and cold when their environment is cold. In hot environments, ectotherm animals can have blood that is much warmer than warm-blooded animals.

Ectotherm animals are much more active in warm environments and are very sluggish in cold environments. This is because their muscle activity depends on chemical reactions which run quickly when it is hot and slowly when it is cold. Ectotherms can convert much more of its food into body mass compared with a warm-blooded animal.

The Pacific Rattlesnake, a fine ectotherm example, is found throughout a variety of places in California, from sea level on the Pacific Ocean, the inland prairies and desert areas, to the mountains at elevations of more than 10,000 feet.

Along the coast north of southern California, the Pacific Rattlesnake has the territory all to itself. In Southern California the Pacific rattler overlaps the range of several other species and subspecies, except that of the large Western Diamondback rattler along the Colorado River and the southeastern California deserts.

A Western Diamondback Rattlesnake

From Lake Tahoe north, on the east side of the Sierra, you might see the Great Basin rattler; from Tahoe south through Death Valley, the Sidewinder (Crotalus cerastes) and Panamint rattlers; along the Colorado River, the Western Diamondback (Crotalus atrox); in the southwestern area, the Red Diamondback (Crotalus ruber) and Speckled (Crotalus mitchelli) rattlers; and in the Mojave Desert, both the Mojave Rattlesnake and the Sidewinder.

A Great Basin Rattlesnake

In the northern areas of their range and at higher elevations, snakes congregate in the fall at crevices in rocky ledges to hibernate for the winter, returning to these places annually. These spots are known as snake dens.

An albino Western Diamondback Rattlesnake

When temperatures begin to warm in May and early June, snakes come out of hibernation. They remain near the den entrance for a few days, sunning themselves, then make their way to where they will spend the summer. Desert summer climates in southwestern USA can produce temperatures into the 110-120 F range. Desert snakes can function without difficulty under these extreme conditions although they too have their limitations. They rarely go more than a mile from their dens. Most snakes are secretive in their summer activities, hunting at night and remaining inactive and out of sight for days at a time during the digestive period after eating a squirrel or small rabbit. Consequently, more snakes are seen in the spring and fall migrations to and from their winter homes.