SNAKES
Sources: most of our information on these creatures is drawn from Stebbins, Robert, 1985, A Field Guide to Western Reptiles and Amphibians, The Peterson Field Guide Series, Houghton Mifflin. See also the various links associated with the UC Berkeley Taxon Lift. Note also an amateur naturalist's Website, Snakes of Arizona, which has some good images for comparison.
Snakes (and lizards) are descendants of a major group of amniote tetrapods, all of which share the characteristic of having two openings in the side of the skull, marking them as Diapsids (a group which includes snakes, lizards, crocodiles -- and also dinosaurs and birds, all of whom are now classed as "reptiles"). Diapsids divide into "Archosaurs" -- crocodilians, birds, and their extinct relatives (dinosaurs, pterosaurs, etc.) -- and "Lepidosaurs" -- lizards, snakes, sphenodon (the living Tuatara of New Zealand), and their extinct relatives. Diapsids display the widest array of species of all amniotes, and have invaded all major habitats from polar regions to deserts to the oceans. The Lepidosaurs are by far the largest non-avian group of reptiles, with some 4,000 species of lizards and 2,700 of snakes. (Strictly speaking, snakes are lizards who have lost their legs.)
Snakes and lizards share distinctive features as "Squamata": determinate, limited-period of growth; light skull-bone construction; mobile-jointed skulls (especially the squamosal-quadrate joint); unique male reproductive organ ("hemipenes"); repeated evolutionary limb-reduction (every major group has at least one species with some degree of it); and "voluntary" tail loss (lost in some species, but definitely an ancestral trait of the group). The earliest Squamata date from the Triassic Era (250-206 MYA).
Snake skin is covered with scales, and most snakes move by means of specialized belly scales. The eyelid scales of snakes are permanently closed but transparent. Like other reptiles, snakes shed their skin periodically, but unlike other reptiles they accomplish this all at once, leaving behind a complete, translucent tube (which has led to celebrating them in some mythologies as symbols of healing and rebirth). All snakes are carnivorous, but none of them chew their food, rather they make use of their mobile jaws (with an especially flexible lower jaw) to swallow their prey whole. Some snakes kill by constriction, others by venomous bites. Snakes have carried the elongated, cylindrical body form to the greatest extreme, yet they have adapted to nearly all habitats and are found on all continents except Antarctica.
SOME SNAKES IN OUR AREA:
Western Diamondback Rattlesnake (Crotalus atrox)
Below left: encountered along the trail near the saddle of Sierra Blanca Spring trail. This one was very difficult to see (as the image reflects; the head is at top center) -- it was heard from close up or would not have been detected. Below right: seen in the Trail Tank wash. This one was crossing the open wash, so clearly visible, but again when under vegetation is well disguised (except for the distinctive black-white-banded tail above the rattle). Note too that the black/white banding is very marked, and that the black and white bands are roughly equal in width. (This latter distinguishes the Western Diamondback from the Mohave Rattlesnake, which also displays some tail banding (see further below)
(Click on each image below to enlarge it.)
Below: Near terminal water in upper Hot Springs Canyon, this diamondback did not move despite our close presence for an extended time, and may have been digesting a rather large bird (judging by the feathers scattered close by):
All of the photos above illustrate how hard it often is to detect a Western Diamondback. While two of these can be seen in these images from head to tail, it's mainly the sharply contrasting white/black-banded tail that catches our attention (the one at the bottom was seen only after it rattled). Our largest rattlesnake, it is also probably the most common in our area, frequenting dry desert as well as lush river bottoms. The Western Diamondback grows to 7' in length, eats a variety of mammals, lizards, and birds, and is often aggressive in defending its turf. It's widely regarded as the most dangerous North American snake.
Blacktailed Rattlesnake (Crotalus molossus)
(Click on image left below to enlarge)
Distinctive features of the Blacktailed Rattlesnake include primarily the black tail (evident at the right above), but black markings on the head between the eyes are often present as well (more visible in the figure on the left, but present on both of these two). Both were photographed in HSC, the one on the left in a cave under Rabbit Ears Saguaro Hill and the one on the right close by the stream in upper HSC. Blacktails avoid the more barren desert, and often hunt near stream courses. They are not usually aggressive.
We have also seen Mojave and Western Black Rattlesnakes on Saguaro-Juniper lands, and also one we thought looked like the Massasauga, but have not yet obtained photographs of these.
Mohave Rattlesnake (Crotalus scutulatus)
While we just noted we haven't managed to obtain local photographs of the Mohave, we did recently receive these from a photographer who, hiking near Tucson on May 11, 2008, photographed this large mass of snakes. (Click on the image for a closeup of the den-hole.)
This closeup image below of the central mass of snakes makes possible good identification of these rattlesnakes as Mohaves (while at the same time documenting the very considerable variation in coloring etc. of these animals). First, note that while the tails above the rattles show dark/light bands, these bands are much fainter than those on the Western Diamondback. Second, The side of the head shows distinctive lines characteristic of the Mohave. Third, the color pattern of the body and particularly the scales along the back are distinctive of the Mohave.
First, In the closeups below of the previous photo above, the tails show distinctive patterns of the Mohave: the black-white banding is less distinctive than that of the Western Diamondback, and the dark bands are usually narrower than the lighter-colored ones. (In the Western D., dark and light bands are usually equal in width.) (Brennan & Holycross 2006, p. 125)
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Second, closeups of the heads show the light stripe behind the eye extends back behind the jaw. This too distinguishes the Mohave from the Western D., whose eye-stripe runs considerably more vertically on the side of the head. (Brennan & Holycross 2006, p. 125)
Third, note first the background color variations in the bodies of the snakes shown in the two images below, which range from green to gray or tan. Western Diamondbacks lack this green variant, and moreover show a "salt-and-pepper flecking" all along the sides. The blotches on the back of these snakes below also fit the Mohave: darker brown than the rest of the body, ringed in black and then in cream color. (Ibid.)
So these give us a good description of Mohave Rattlesnakes, which are large and potent with hemmorhagic toxins. As we said, these images are from the Tucson vicinity, and we have yet to photograph our local variants, which may show some differences from the above. Moreover, we can't yet credit this photographer, but will do so when we get the person's name.
Coachwhip (Masticophis flagellum)
(Click
on each image to enlarge it.)
The Coachwhip shown above (Cascabel Road, about Mile 19) first appeared to be dead by virtue of its odd position and its lack of movement (on the left). But the date was January 2001, and its sluggishness was no doubt associated with the day's low temperature. After the second photograph (middle left), it suddenly sprang into slow but steady motion, finishing its road crossing just as a large back-hoe vehicle lumbered by.
The name of this snake derives from its "braided-whip" scaling (just noticeable in the single photo at right above, behind the neck), as well as from its slender body and tail (top left). This specimen is probably of the "Sonoran" subspecies, since it has the reddish brown crossbands above separated by light pink interspaces (visible in the middle and right photos at the top). The black crossbars on the neck are also signs of the Coachwhip, whose coloration is highly variable. Black phases of this snake are also present in our area.
Coachwhips, unlike many of our Sonoran Desert snakes, are often abroad during the day, and (in hot weather) they crawl with great speed (one popular name is "Red Racer"). They are sighthunters, who rise up to scan their vicinity for prey, a behavior called "periscoping", and if approached too closely they may become aggressive, confronting, hissing, striking. (Herpetologist Hanna Strass reports a corruption of their Genus name as "Nastycophis", alluding to the bloodied hands that often result from attempts to catch them.) They eat small mammals, birds and bird eggs, lizards, snakes, insects, and carrion.
Sonoran Whipsnake (Masticophis bilineatus)
The snake below was encountered at the HSC Windmill in August 2003. The first image shows the distinctive bluish gray color running from its head toward the middle, and two light-colored stripes on each side (which fade rapidly toward the tail).
The second image (below) shows how the blue-gray color fades to a lighter and creamier tone along the latter two-thirds of the body (which is also cream colored below).
Below you see the full length of the snake, which we estimated as about 5 feet. What a beautifully graceful animal!
While the Sonoran Whipsnake is often attracted to streamsides (as above, moving along the Windmill's leaky concrete water tank), it ranges from saguaro-paloverde uplands to the pine-oak belt of the mountains. It climbs bushes and trees, and eats frogs, lizards, and small birds.
This specimen, below (unfortunately for it, a road-kill found along the Cascabel Road), looks like a member of the whipsnake genus, but its coloring looks more like a California Whipsnake (not found in our area) than like the Sonoran. On the other hand, herpetologist Dennis Jex suggests this is most likely a Western Patch-nosed Snake (Salvadora hexalepsis), which is present in our area. (Unfortunately, the resolution of this photo is insufficient to tell whether the characteristic large scale wrapped back over the nose is present.)
Ringneck Snake (Diadophis punctatus)
The above pictures of the Ringneck Snake are not very good, but they do provide the main indicators of the species: blue-olive in color, with a dark head and conspicuous orange neck-band; its belly is red (brighter where closer to the tail), and its scales very smooth. When faced with an intruder, it may curl its head and upper body up quite high, revealing its startlingly bright underparts. Ringnecks prefer moist environments (particularly forests), and are seldom seen in the open (though we encountered one crossing the wash below the Trail Tank during the rainy season). This one was crossing the Cascabel Road near mile 19 one fine October day. (We will have better images when we begin inserting video movies rather than stop-action, which these shots are.)
Ring-necks are usually found under ground or wood, or stones. They eat small amphibians, lizards, small snakes, worms, and the like.
Black-necked Garter Snake (Thamnophis couchii)
The distinguishing feature of this garter snake is the two large black blotches at the back of the head, separated by its whitish-to-pale-yellow mid-dorsal stripe. Mainly found in streams near foothills and mountains (this one in the Hot Springs Canyon Stream in July of 1995, photographed by Mark Apel), but it also occupies desert and grassland, and in wet weather it may wander far from water. Mainly diurnal, it eats frogs, toads, tadpoles, crustaceans.
On August 31, 2008, we were driving along Cascabel Road near Milepost 16 when we saw a pair of vultures standing in the middle of the road. As our vehicle approached, they flew off, and we drove slowly up right beside this small Black-necked Garter Snake, which remained motionless in the roadway gravel. Thinking it might be dead, we got out of the vehicle (it was 5:38 pm) and took the following photograph Below: (Click on the image to enlarge it)
This was a rather small snake, about a foot long, and while it didn't look injured we thought it might be immobilized or even dead (roadkill injuries are not always visible from above). So we moved around, got closer and, as we took the following picture, could see that it was testing the vapors with its tongue, so it definitely was anyway not dead: (Click on the image to enlarge it)
Satisfied
with our imagery, we then moved to prod the snake with a stick, and it ran off
with a flash under the vehicle, quickly dashed off the roadway up the gravel siding
and disappeared in the adjacent shrubbery. We thought the vultures must have "cornered"
it in a sense, standing on each side of it, and were preparing to peck at it when
we arrived. As we drove off they glared at us from the roadside some 40 yards
further on.
Checkered Garter Snake (Thamnophis marcianus)
Naturalists Linda Lindsay and Hanna Strauss found this snake, very recently dead, on a well-vegetated bank of the San Pedro River permanent stream in April 2005. (This is the only location where we have seen this snake species.) Large waterbirds standing nearby had flown away as we approached, suggesting that one had probably just killed and then dropped it.
Initially, we thought we were seeing a Mexican Garter Snake (Thamnophis eques). Populations of the Mexican Garter Snake are severely fragmented and isolated due to loss and destruction of suitable habitat, which consists of riparian areas with permanent water, streamside vegetation for cover and native prey species. They are approaching the condition of an Endangered Species in the United States.
However, Herpetologist Matt Goode, Research Scientist in Wildlife Conservation and Management at the School of Natural Resources, University of Arizona, tells us that this snake is actually a Checkered Garter Snake (Thamnophis marcianus) (click on the image for a close-up view).
Unlike the rare Mexican Garter Snake, Checkered Garter Snakes are common in our area. Matt Goode says, "They look an awful lot like checkered gartersnakes, but one of the best ways to tell them apart is the cream-colored line on the side of the body covers scale rows 3 and 4, whereas it only covers scale row 3 on a checkered gartersnake. [Examining the frozen corpse closely under magnification, we could see that the line does cover only one scale.) Also, checkered gartersnakes have a lot more blotches or checks than Mexican gartersnakes."
Gopher Snake (Pituophis melanoleucus)
Gopher Snakes in our area are yellow or cream-colored, with black, brown, or reddish brown blotches on the dorsal side, usually more widely spaced toward the tail than on the body (quite noticeable here in the photo above) and -- in the Sonoran variety, they darken toward the rear (also evident here -- the contrast between light and dark coloring sharpens noticeably). This gopher, photographed along Cascabel Road in May 2004, is one of the longest we have ever seen in our area, probably more than seven feet long.
Usually there is a dark line across the head in front of the eyes and from behind the eye to the level of the jaw. This is clearly visible in the head photo below left (our very large snake shown above), but not so clear on the much younger snake seen in Teran Wash in April 2007, below right. :(Click on each of the two images below to enlarge it.)
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A distinguishing feature on the head is the four prefrontal scales in front of the eyes ( evident in the enlargements of both these snakes). (Compare rattlesnakes in this regard -- the shape of the head is also quite different -- not to mention presence/absence of rattles.) The color patterns behind the head are distinctive.
Below, our April 2007 gopher may have ventured out somewhat early in the season, a cool day. We encountered it just past midday, but it was loath to move (though it sampled the air with its tongue sporadically, thus showing life). It only moved on well after the photographer departed. (We estimated this one at about 4 feet long.)
Below, a gopher snake hides under the overhang beside the Sierra Blanca Spring. (The yellow-tan object at lower left is a work glove.) The light-colored tip of the snake's tail is clearly visible to the right of lower center; look more closely to see the bright red blotches of this snake elsewhere: (click on the image to enlarge it)
Gopher Snakes are very widespread in the West, living in a variety of habitats from lowlands to high mountains and from deserts to coniferous forests. Both good climbers and burrowers, they are active mainly by day (a habit fatal to some along the Cascabel Road, though the one shown at the top [near Milepost 21] was escorted away from its vulnerable location, and it moved quite swiftly).When aroused they may hiss loudly, sometimes flatten their heads and vibrate their tails (perhaps an adaptation imitating rattlesnakes, for which they are sometimes mistaken by humans). They kill by constriction -- rabbits, rodents, birds, eggs, occasionally lizards and insects.
Common Kingsnake (Lampropeltis getulus splendida)
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This one (in the photos above and below) was seen as a roadkill on Cascabel Road near Teran Wash, September 2000. Its length was 16-20". Above left shows its belly, above right its appearance from above. (Click on right-hand image to enlarge.)
Below left: the head of this snake seen from above; below right: from the side.
Widely distributed through the Southwest (and elsewhere) three subspecies are present in our general area. The most common pattern of color is the alternating bands of black and white (or pale yellow), the pale bands broadening on the belly. This pattern is the one shown above. (A black form without bands also appears in our area; see more below.) The Common Kingsnake occupies a wide variety of habitats, from desert to swampland to coniferous forests. It eats snakes (including rattlers), lizards, small amphibians and reptiles, frogs, birds and bird eggs, and small mammals.
This Kingsnake (below) was killed by a predator (probably a raptor) and found on the ground at the mouth of Sierra Blanca Spring Wash one afternoon in October 2005. It was very recently dead (probably the same day -- it had not been seen earlier in the day at this location). Its spine had been broken in at least one place, and it had been lacerated in several, but nonetheless the corpse had been abandoned. Perhaps the raptor had struggled with it at this location, then abandoned it to die. (Click on the image to enlarge it.)
We saw a strikingly different color pattern in the Kingsnake in Lower Hot Springs Canyon Wash beside an artificial pool in May 2006, shown below:
This one closely approximates the "G. splendida" variety shown in the Kingsnake/Milksnake webpage -- see that link for images of Kingsnake varieties. Closer looks at our Kingsnake above are the following: (Click on each image to enlarge it.)
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Particularly in the image at left, note the remarkable frontal pattern this snake's head presents in a close-up view, looking (at least to a human observer) like a small face with a very small mouth. At far right, You can see that the yellow banding on the belly, while wider than the back's, does not obviously become a dense pale band, though it may be that the alternating sets of light and dark belly scales do run all the way across the belly.
Below, the tail portions are highlighted as the snake disappears into a tangle of dead grasses. (Click on the image for a close-up view.)
Below, we encountered a young snake -- about the thickness of a man's little finger --moving about in grasses near the Red Tank in late September 1999:
(Click
on the image to enlarge it.)
Noteworthy in this photograph (and more clear in the enlargement) is the distinctive color pattern on the head about the eyes, which is visible in the lower-right quadrant, sticking out from below the hind part of the body which runs diagonally from lower left toward upper right. We inferred that this was a juvenile Common Kingsnake, but Hanna Strauss of the Southwestern Herpetologists Society tells us that this might instead be a "juvenile claris (yellow) phase Longnose Snake (Rhinocheilous lecontei lecontei)," which is a common snake in our area and closely related to the kingsnake. In her personal communication, Strauss elaborates on the distinction: "Juvenile desert Kings are very cleanly marked; the bands are almost pure white and cleanly delineated from an almost pure black background, and extend all the way down to the belly scales of the snake. Longnose Snakes, such as the one depicted in your site's image, have saddle-like markings rather than the clean bands found in Kingsnakes." However, she also adds that the dominant Common Kingsnake in our area, the L.g. splendida, does have "blotchy speckled coloring as well as almost clean banding", and so the photo above doesn't give enough detail to make a firm decision. Thanks, Hanna. (Compare this head image with the closeup further above.
The Stebbins books shows the Longnose Snake having pinkish spaces between the black saddles (Pl. 37), but the accompanying description indicates cream colored spaces as an alternative. Its habit is nocturnal, it is a good burrower, and eats "lizards and their eggs, small snakes, small mammals, and occasionally birds." (p. 196)