The Pinacate region is named for the desert stink beetle (Eleodes sp.) which is commonly found there. The Aztecs called this beetle "pinacatl" in their Nahuatl language. And so this region of volcanic drama and stark beauty is in fact named for a lowly but distinctive insect.
Arthropods abound in the Pinacate and Gran Desierto in spite of the heat and dryness. Centipedes (Class Chilopoda), millipedes (Class Diplopoda) and arachnids such as bark, stripe-tailed, and desert hairy scorpions, desert tarantulas, solpugids (sun spiders) and pseudoscorpions are widely recorded within the Pinacate region.
We observed the inverted cone-traps of ant lions (Myrmeleon sp.) and the tracks of sand treaders (Macrobaenetes sp.) in the dunes areas. Dragonflies (Libellula sp.) flitted about in spite of the near absence of water. A tarantula (Aphonopelma chalcodes) was observed during a night hike at Red Cone.
Only the Sonoran Desert amphibians best adapted for extreme aridity are present in the area. The Sonoran Desert toad (Bufo alvarius) and Great Plains toad (Bufo cognatus) are largely restricted to the Rio Sonoyta drainage.
Only the red-spotted toad (Bufo punctatus) and the desert spadefoot (Scaphiopus couchi) are found in the Pinacate interior, surviving by their proximity to the tinajas, rocky water catch-basins scattered through the area.
During drought periods from April to August, virtually all of the Pinacate tinajas are dry. Therefore these amphibians must wait patiently underground for sufficient rainfall to spark surface activity and fill these ephemeral breeding sites.
Most of the reptiles of this region are typically associated with the Lower Colorado River Valley subdivision of the Sonoran Desert. Some have substantially larger distributions elsewhere.
The most striking feature distinguishing many Pinacate lizard and snake populations from others in the lower Colorado River valley is the distinctly dark overtone in the color and pattern of many individuals.
While these darker tones are generally within the range of normal color variation for the species, this observation does suggest a trend of natural selection for darker shades in species inhabiting lava flows, dark desert pavement and cinder flats.
Some desert reptiles, particularly lizards, are capable of varying degrees of color change (metachrosis) from darker to lighter shades, aiding both in thermoregulation and background matching.
Although the herpetofauna of the Pinacates is surprisingly diverse, some Sonoran Desert species are conspicuously scarce or absent.
The desert tortoise (Gopherus
The reticulated Gila monster (Heloderma s. suspectum) is also rare in this area (Fig. 11c). Specimens have been recorded from the Celaya Crater and at the base of the Sierra de la Salada north of the Pinacate interior. Another was found 16 miles west of Sonoyta on Highway 2 near the western range limit for the Gila monster in northwestern Sonora. Mexican naturalists tell us "el escorpion" is not found on the Pinacate lava.
The RED-BACKED WHIPTAIL (Cnemidophorus burti xanthonotus) is a western race of the giant canyon spotted whiptail, reaching a snout-vent length of about 5.5 inches (13.7 cm). We observed specimens in McDougall Pass on the way to McDougall Crater. Although not widely distributed in Mexico, it is known from the borderlands in the Ajo Mountain area of Organ Pipe Cactus National Monument.
The more common and widespread ARIZONA DESERT WHIPTAIL (Cnemidophorus tigris gracilis) is found throughout the Lower Colorado River Valley except in the steep mountains and dunes. Whiptails are most active during the morning and late evening hours as they hunt invertebrate prey in characteristically jerky fashion.
The SOUTHERN DESERT HORNED LIZARD (Phrynosoma platyrhinos calidiarum) is the common horned lizard of the lower Colorado River valley. It has adapted well to the cinder ash and lava of the Pinacates where, like other horned lizards in their habitats, it a master of camouflage. In the Pinacate, specimens are significantly darker than those living on lighter substrates. The desert horned lizard accepts a wide variety of food, feeding not only on ants, but also other insects, spiders, and occasionally plant material.
The SONORAN SPINY LIZARD (Sceloporus magister) is the largest spiny lizard found in North American deserts. Although a good climber, it is often found on the ground where it forages for insects, leaves and berries, and occasionally smaller lizards.
The LEOPARD LIZARD (Gambelia wizlizeni), the top lizard carnivore in the Sonoran Desert, reaches a snout-vent length of 5.75 inches (14.4 cm).
It can achieve substantial speed by running on its hind legs only, using the long tail as a counterbalance.
Other lizards are commonly eaten, as are pocket mice, arthropods, and occasionally some plant material.
Leopard lizards bite fiercely in defense. Their tails break easily along fracture planes in the vertebrae, an adaptation called tail autotomy.
Leopard lizards are nowhere as common as most other species in the area. The females develop beautiful reddish-orange markings along the body and tail during the breeding season which fade rapidly after mating.
The DESERT IGUANA (Dipsosaurus dorsalis) is usually associated with creosote bush, upon which it feeds and beneath which it often burrows.
It is well-adapted physiologically to the desert climate, enjoying a higher optimum body temperature than any other North American lizard. This enables it to remain active after other species have sought refuge from the heat.
Like the leopard lizard, it is a larger desert lizard, reaching 5.75 inches (14.4 cm) snout-vent length. Conspicuous over most of its range, it basks prominently, conveying a distinctly whitish appearance from a distance.
Specimens found near the Sierra Pinacate were noticably darker than those seen some distance from the cinder ash areas.
The COLORADO DESERT FRINGE-TOED LIZARD (Uma notata) is superbly equipped for life on the shifting sands of desert dunes. The light beige and ocellated color pattern blends subtly with the fine sand.
The fringe-like scales on the toes provide a sort of "snow-shoe" effect, preventing slippage as the lizard races over the dunes surface.
The nasal valves and counter-sunk lower jaw enable efficient escape from predators when the lizard dives head-long into the sand .
The FLAT-TAILED HORNED LIZARD (Phrynosoma mcalli) is similarly specialized, living only in the windblown dunes of the Gran Desierto and Algodone Dunes.
Equally cryptic in its sandy domain, it is surprisingly fleet of foot, often running swiftly over the sand in a manner similar to the sympatric fringe-toed lizard.
More commonly, it avoids attention by flattening against the sand or burying itself. Its diet is typical of most horned lizards, consisting chiefly of ants.
The COMMON CHUCKWALLA (Sauromalus obesus) is at home in the dry desert mountains, lava flows and craters of the Lower Colorado River Valley.
It is often more abundant near tinajas where it finds sufficient food in the highly seasonal and ephemeral plant growth.
In the Pinacate, the chuckwalla population is generally dark in color, rendering them less conspicuous to hawks and other predators. Dark colors absorb solar warmth rapidly, reducing the thermal window for summer activity, but extending activity at other times of the year.
ARIZONA ZEBRA-TAILED LIZARDS (Callisaurus draconoides ventralis) is common on gravelly soils in the Lower Colorado River subdivision, seeming to tease with their gently wavering tails as they peer back from a safe distance.
The COMMON COLLARED LIZARD (Crotaphytus collaris) inhabits desert mountains in the eastern portions of the LCRV while the MOHAVE COLLARED LIZARD (Crotaphytus insularis) occurs further west.
Collared lizards are saxicolous (rock-dwelling), maintaining territories among rocks and boulders while watching for insect or lizard prey.
Although records exist for the SOUTHWESTERN SPECKLED RATTLESNAKE (Crotalus mitchelli pyrrhus) in the Pinacate region, much of the area offers suitable habitat and it is probably a common snake on the rocky, lava-strewn slopes .
The speckled rattlesnake population in Arizona's Tinajas Altas Mountains just 60 miles or so to the northwest are a lovely white in color. This contrast within such a short geographic distance underscores the dynamic forces of natural selection which are constantly shaping the makeup of living organisms.
A WESTERN DIAMONDBACK RATTLESNAKE (Crotalus atrox) rests quietly beside a creosote bush. Its color and pattern blending gently with the light, shadows and sandy gravel .
The Pinacate is many things to many people .
Some consider it a vast hostile wasteland.
To others, its very desolation holds a magnetic attraction that imparts great worth.
To a privileged few it is a desert wonderland, a "real" desert in the midst of the great Sonoran expanse .