How To Identify A Snake By Its Shed Skin

Often it is possible to identify snakes by their shed skins alone (y'all tin practise so too, hither). I have had some pretty serious exercise of this skill this week. In the past three days, I accept found iii fairly fresh ophidian sheds on islands in the Matanzas River. I am here doing evolutionary biological science research on brown anole lizards, which you lot can read more about here and hither, just information technology's impossible (for me, at least) not to be on the sentinel for snakes and snake-related objects, such as shed skins. Snakes don't typically hang effectually the site where they shed very long (don't worry, I looked), but the sheds themselves have many characteristics that aid in identifying the species they came from.

Two of the 3 sheds were found right outside the entrance to a gopher tortoise couch. These burrows are built by the tortoises for shelter, and many other animals, especially snakes, use them also. They can be equally long as 40 anxiety and as deep at 10 feet. Although many snakes spend a significant amount of time underground, they usually come up upwards to the surface to shed their pare All snakes must practise this in one case in a while, typically every three weeks to 2 months, depending on their growth charge per unit and need to heal injuries or slough off parasites.

Archway to a gopher tortoise burrow

Although snakes shed their skin in a single piece, the shed is very delicate and can be tattered or torn easily by wind or other animals. Most often, though, a shed is either torn apart by the serpent as it sheds, or tears itself autonomously every bit a result of drying out (information technology is wet when the snake sheds it off, as a result of lymphatic fluid excreted by the snake's integument to aid in the shedding process). Sheds are easiest to place when they are freshly shed, ideally before they have dried out entirely, which only takes an hour or and then in the hot Florida lord's day. Luckily for me, the ii sheds I constitute exterior the tortoise burrow had probably been shed merely most an 60 minutes or so before I found them, so they were fairly intact. Still, one was torn in half, not a big deal from an identification perspective, and the other had suffered some tattering of the head, which is more serious but non fatal.

The beginning thing to notice is the overall size of the shed, as this can rule out many species if the shed is big, which these were. Information technology's important to recollect that you could exist dealing with a juvenile snake, so small overall size does not necessarily hateful that 1 is dealing with a small-bodied species of snake. The shed peel is necessarily larger, both in length and girth, than the torso of the snake that shed it, since the shed has to stretch in club to be pulled off the snake. Still, the relative proportions are often fairly similar, and both length and width can exist clues to ophidian body size and shape.

The sheds I collected measured 72" and 60" in length, plus or minus a few inches to account for imperfect measurement of the difficult-to-stretch sheds. The ventral scales at the halfway signal of the trunk were nearly 1.v" and one.25" wide, respectively, and then I could tell that these were both fairly heavy-bodied snakes, fifty-fifty for their bully length. This narrowed downward the pool of possible species considerably, but in that location were nevertheless several candidates, including indigo snakes, either of the two large rattlesnakes native to Florida, rat snakes, corn snakes, and pine snakes. Coachwhips also attain these lengths, but are relatively slender.

Other easy clues narrowed the species pool further. The dorsal scales (those covering the top and sides of the body) were more often than not smooth, although the middorsal scales of the larger shed showed some slight keels. Keels are when there is a ridge running lengthwise down the center of the scales, similar to the keel of a boat. The texture of the scales (keeled or smooth) is preserved in the shed skin, and can be an important clue to the identity of the shedder. Rattlesnakes, watersnakes, and pino snakes all have strongly keeled scales that feel rough to the touch – I knew that these species were non responsible for the shed when I saw that the scales were smooth in texture. Furthermore, counting the number of rows of dorsal scales, typically halfway between the caput and the tail, can give further insight into the identity of the snake. These sheds both had 27 scale rows at midbody.

The larger shed

Patterns are often preserved in shed skins, but without their colors. High-dissimilarity patterns are particularly evident, only typically are only clearly visible for a brusque while after the skin has been shed. These can be important clues, but they are difficult to interpret. Good lighting is often required to make out the pattern of a snake shed. These snakes had slightly different patterns. The larger shed had two dark stripes running longitudinally downwardly the entire body, virtually the center of the dorsum. The smaller had a similar pattern, merely the infinite between the stripes contained alternating nighttime and calorie-free blotches with dark edges, especially about the caput. Neither shed had any evident blueprint on the ventral scales.

The head of the larger shed

Between the calibration row count and the pattern, I had a pretty adept thought what genus these snakes were in. To identify to species, nonetheless, is often trickier, because information technology commonly involves examining the scales of the caput in detail. This requires one) having the caput to look at and 2) a caste of finesse, because the head is often the most delicate part of a shed. Additionally, the caput is often scrunched upward inside of the inductive part of the body, as a upshot of the behavior of the serpent during shedding. Extricating the caput is not unlike performing a autopsy. I have establish that it is helpful to photograph the head at every stage of dissection, because yous might destroy certain features in pursuit of access to others, or just from even the lightest handling. Too, details are sometimes evident in macro photographs that are not obvious on the shed itself.

The smaller shed

The scales of the head of colubrid snakes each have special names that are adamant past their organization with respect to the optics, mouth, nostrils, and to i another. The easiest scales to count are the upper (supra) labials. These are the scales along the upper lip. One or 2 of the supralabials are typically in contact with the bottom of the heart, which can exist an of import characteristic. The frontmost scale on the upper lip is called the rostral and is located front and center on the nose of the snake, but there is not much variation amongst species in the characteristics of the rostral, so it's non very informative One of these sheds had 8 supralabials on each side of the caput, the iv^th and five^th of which were in contact with the centre; the other was likewise destroyed to count, particularly toward the rostral (where many snakes begin rubbing in social club to slough off the shed). Other similarities included two pairs of prefrontal scales (the scales above the rostral and between the supralabials, on the bridge of the nose), a divided nasal scale (the calibration behind the rostral that contains the nostril), one loreal (the scale between the nasal and the preoculars), one preocular (the scale behind the loreal and in front of the eye), two postoculars (the scales behind the eye), and a 2+three+3 temporal formula (the numbers of scales in each of the three rows posterior to the postoculars). On the basis of all these similarities, I ended that these were probably the same species of snake, which I think is Pantherophis [Elaphe] obsoletus quadrivittatus, the Yellow Ratsnake.

A much smaller yellow ratsnake that I defenseless this week

The size and pattern discrepancies could be solved in two ways. The smaller of the ii snakes could have been a corn serpent (Pantherophis guttatus), which is what the pattern reminded me more of. However, rat snakes are blotched with a similar blueprint equally (simply dissimilar colors than) a corn snake when they are immature. Although this pattern fades with age, faint traces of it may be evident even in very large snakes, and these traces may be more than axiomatic in shed skins than on the bodily snake. Information technology wouldn't exist unusual to find rat and corn snakes cohabitating in the same tortoise couch, especially considering there were but two burrows on this island that I could find. The other explanation is that both sheds came from rat snakes, one male person and the other female. Although at that place are no consistent pattern differences between male and female rat snakes, the slight keels on the middorsal scales of the larger shed are typical of male rat snakes, whereas the completely smooth scales of the smaller shed are consistent with female rat snakes. Furthermore, the larger size of the male is typical of all snakes that take male person combat, including rat snakes. Finally, and about convincingly, the tail of the larger specimen made up 17% of the total length, whereas the tail of the smaller specimen, while slightly more dilapidated and harder to mensurate, only fabricated up well-nigh 11% of the full length. This is consistent with sexual dimorphism in tail length observed in nearly every species of snake.

Because both snakes were in the aforementioned place at the same time (judging by the condition and likely historic period of the sheds) and were dissimilar sexes, I think it'southward more likely that they were the same species, yellowish rat snakes, possibly a mating pair. Why they both shed before (or afterwards) mating, I couldn't say – perhaps the snake version of an after-sex cigarette?

Whereas blotched and unblotched adult rat snakes are possibilities, I have never seen or heard of unblotched adult corn snakes, and in any instance, these would have been some big corn snakes, especially the male. They were pretty big even for rat snakes – the record rat snake length is 72" (continue in mind that the measured lengths of the sheds are several inches longer than the lengths of the snakes, because the sheds are stretched out).

The tertiary snake shed I found a few days earlier on the aforementioned island, but abroad from the tortoise couch, in a sandy surface area. This was a trickier one, because I only establish office of the shed – this time both the head and tail were missing. These are the 2 almost informative sections of a shed, the caput for reasons I described above, and the tail considering of the ability to tell the sex (given also the total length) and because the subcaudal (nether tail) scales can give you information near the family of snakes to which the owner of the shed belongs. All I had to work with were the dorsal and ventral scales, and the limited pattern I could see. I could also tell that this serpent was robust, non slender, which eliminated a few species, such as the Racer and Coachwhip, and fairly large, which eliminated several more pocket-sized-bodied species.

Ventral design of rainbow snake shed

The dorsal pattern of this shed was faint, only I thought I could make out a few stripes similar to those of the rat ophidian, but thinner. I looked closely at the ventral design, which was obscured in about places but quite articulate in a few spots. The gestalt of the design reminded me of something I had seen earlier, but I couldn't quite identify it at first. I looked more closely at the rest of the shed. The dorsal scales were completely smooth, with no hint of keels. They were in 19 rows, which is an important piece of bear witness. I knew that this was not a pino snake, rattlesnake, cottonmouth, rat snake, or kingsnake, all of which take keeled scales, a greater number of dorsal scale rows, or both. Only two large snakes in Florida take 19 dorsal scale rows – the mud serpent and the rainbow ophidian. These are secretive, fully aquatic snakes with specialized diets and ambiguous habits; both are rarely seen. You might inquire why the shed of a fully aquatic snake would exist found on dry country. The interesting thing about mud and rainbow snakes is that they lay eggs, unlike virtually other species of aquatic snakes. Females of these snakes must come onto land to lay their eggs, much like female person turtles. I take never heard that they come to land to shed, but obviously this ane did.

Ventral design of rainbow snake shed

Based on the habitat and the particulars of the ventral blueprint, I call up it's much more than probable that this was a rainbow snake (Farancia erytrogramma) than a mud snake. Because the island I was on is in the estuary, shut to the body of water, there are almost certainly American Eels in the river, which are the primary nutrient of rainbow snakes. Mud snakes consume giant aquatic salamanders, specially sirens and amphiumas, which do not inhabit salty water – their virtually common habitat is isolated acidic wetlands, such as Carolina Bays. To detect either of these species is a rare treat. To find the shed of ane is probably even rarer, although I'm not sure of that. I was pretty excited about this find, because the rainbow snake is one of my very favorite snakes.