Although snakes are both common and diverse in the Arizona Upland, they are much less conspicuous than lizards.
Nearly all spend most of their lives secluded in a variety of refugia, awaiting appropriate climatic and endogenous cues to allow activity.
Of the 21 snake species found in Arizona Upland habitat near Tucson, only the 5 rattlesnakes and western coralsnake (Micruroides euryxanthus) are dangerously venomous to people.
A few others are opisthoglyphs, snakes with enlarged grooved teeth in the rear of the upper jaw which conducts relatively mild venom designed to immobilize small prey. One of the most familiar of these is the lyre snake (Trimorphodon biscutatus), a tropically-derived rock-dweller which feeds on lizards and small mammals, including bats.
Rattlesnakes
are among the best-known and least understood of the Sonoran Desert wildlife
community. The rocky Arizona Upland slopes are inhabited by three distinctive
species and occasionally visited by two others.
Arizona Upland populations rarely surpass four feet. Here, large winter den congregations are unknown but smaller dens of a a score or more snakes are documented.
The relatively mild Sonoran Desert winters render deep, well-insulated den sites unnecessary.
The
western diamondback is most active from late March through October, but has
been recorded afield every month of the year in Arizona and further south.
Male combat and mating occur following emergence from hibernation.
Diamondbacks become more crepuscular as spring warms and chiefly nocturnal through the summer.
Everywhere it is unnecessarily feared and often killed on sight...
...but the ecological importance and resilience of this western monarch is evidenced by its persistence in the face of constant human persecution.
Ironically, it is the sophisticated evolutionary gift of venom and correspondingly efficient delivery apparatus that commands such respect and fear.
Rattlesnakes are frequent prey for a wide range of desert carnivores ranging from red coachwhips and common kingsnakes to hawks, coyotes, and javelina.
They in turn are key predators in the energy web, providing checks and balances for lizard, rodent, and rabbit populations.
The black-tailed rattlesnake Crotalus molossus) is also wide-ranging in distribution and habitat but is less common where it is sympatric with the western diamondback.
Black-tailed rattlesnakes are most common in woodland habitats above 5,000 feet in elevation. The highland populations are typically dressed in yellow or greenish ground colors with contrasting black facial mask and tail.
In the Sonoran Desert, the black-tailed rattlesnake descends into the Arizona Upland where it assumes more muted tones in synchrony with the rocky, less shadowy microhabitat.
The tiger rattlesnake (Crotalus tigris) is largely endemic to the Arizona Upland bioregion of the Sonoran Desert and the tropical thornscrub and deciduous forests in Sonora and northern Sinaloa, Mexico.
This rock-dwelling small-prey specialist is easily overlooked as it aestivates through much of the summer.
When the summer monsoons release their torrents from July to September, tigers rattlers, most often males, prowl the steep rocky slopes, their purpose still not clear but probably in search of sedentary females.
Their well-known preference for the warm, humid conditions following summer monsoon storms is a clue to their dry tropical forest origin.
Tiger rattlers are readily distinguished from other rattlesnakes by the large rattle and unusually small head. It is notably mild-mannered, rarely offering to bite unless unduly annoyed.
The tiny head may be adapted to extract small mice and lizards from rock crevices, though larger prey is sometimes taken.
The
particularly virulent venom ranks among the most potent known for any rattlesnake.
|
|
|
