Plestiodon Skinks -- Getting it Right!

8/12/2020

A Brief Moment of Clarification

I first have to say, I do not often write a section that is: my opinion and these are the facts why. In these rare moments, I try to make it as clear as possible by saying a, "I believe based on experience" or "Personally I find" statement. Let me be clear, this following statement is not my opinion: field guides, educational organizations, and experts have been (probably) unknowingly spreading misinformation for decades on the genus Plestiodon. Now, I take an accusation like this seriously. I would not say such a thing if it were not true. I am highly disappointed in what these groups portray these species to be, when scientific papers show the complete opposite. Maybe it is easier just to say look for this and this, but when one of these "key traits" is inaccurate, this hurts more than helps. These sources often say one has to see the scales under the tail, or count supralabials to get a positive identification. This is all total, and udder garbage. Somewhere this rumor or idea started, and the butterfly-effect has caused it to roar throughout the herping community. This causes dozens, if not hundreds, of misidentifications, and sabotages our understanding of these species. I was one of the first to note the skinks on Galveston Island in Texas were Southeastern Five-lined Skinks, simply off of dorsal photos of dozens of specimens on iNaturalist.org. After three years of me nit-picking details and citing papers, finally Chris Harrison and Michael Price went down to Galveston to get under-tail photos, and finally Southeastern Five-lined Skinks are considered an introduced species to the island. I constantly have to clear-up these misconceptions.

Common Five-lined Skink | © Ty Smith

Now, I am reviewing Southeastern records in Virginia to build an accurate range map for this species in this state. I have found several, single county records have been misidentified by even prominent herpetologists, simply because they are focusing on one feature to ID that is out dated, or they are looking at an unusual specimen. These three species are not identical, and can often be distinguished solely off their pattern, though not in the way you may think. If I had a nickel for every "You cannot ID these unless you have the scales under the tail, or count supralabials" I have heard people quote from some random source... Well, you know how that line ends. My response is simply, "You may not be able to ID these unless you have the scales under the tail, or count supralabials, but that is because you have never been told how to properly ID these skinks." And that is okay. If you lived your whole life being told one thing and have never seen it done a different or better way, you would never know. So, I challenge you to just forget what you know about skink ID and take some time to try these methods to see if it makes sense.

Common Five-lined Skink | © Ty Smith

Southeastern Five-lined Skink | © Ty Smith

Death to the Supralabial Count

Dramatic title? Well, I want you to remember that supralabial counts are NOT an accurate way to identify these skinks. We as educated herpers need to start the movement to write this out of history. I have never been able to track down the source for this, as it was never published in a scientific journal that I have found, and if you find it somewhere in an outdated paper, please email us the link. There have been several studies into the accuracy of these counts, and it seems at best they are ~70% accurate. Now, this does not exactly mean three out of ten Common Five-lined Skinks will have five labials; it means anywhere between two to three out of five will have five labials on one side or the other. And yes, commonly Five-lined Skinks will have four supralabials one one side and five on the other. In fact, we discovered one state herpetological society (it was not VA, but I am not here to call anyone out) had accepted one Common Five-lined Skink as two records; a Common and a Broadhead. They told the observer, "You had to have unknowingly photographed a second animal." The skink, as the observer thought, had simply turned around, giving the observer a right side with five supralabials and a left with four... That said, I do not often see Broadheads with four supralabials. All I can figure is this "rule" came from the initial write-up suggestion the Broadhead almost always has five supralabials. With that, I have indeed seen several Broadheads with four, and one or two with even six. I have even seen Commons with six supralabials as well. Just in case you are skeptical, I have a barrage of facial scale count photos below of all three species.

Those Under-tail Scales

This is a decent way to distinguish the Southeastern Five-lined Skink from the Common Five-lined Skink and the Broadhead Skink, but far from the only. When you are learning, and you wanna test yourself, you can always look under the tail for a close answer. But what do you look for? Well, past the vent (cloaca) there is a row of scales which run down the center of the tail, that we refer to as the postventrals or midventrals. Commons and Broadheads have wide postventrals while these are split on Southeasterns, into two equal rows that are approximately the same size as the adjacent scales, with a more prominent outline. There are some caveates though... Regrown Common tails often grow back with smaller postventral scales. Sometimes, the original postventral scales are only 5-10% larger than the adjacent scales. Finally, sometimes scales split or fuse (remember this, it is important throughout this article). This means sometimes you get abnormalities on a section or majority of the tail. Most skinks that are misidentified to Southeastern, are victims of one of these cases above. Remember, if you catch a dozen skinks, you are bound to find some variability, and this means that one field mark is rarely a good method to ID abundant species.

Common Five-lined Skink with scale abnormalities for a section for the midventrals | © Ty Smith

Common Five-lined Skink displaying 2 postlabials (black) and 4 supralabials (white) | © Ty Smith

Now, the postlabials are a spectacular guide to whether or not you have a a Broadhead Skink or not. Broadheads have one (rarely two) small postlabials if they have them at all. Southeasterns will have two medium-sized postlabials, and Commons will have two, large postlabials. Look at the photo above where I have both scale types counted and color-coded.

Southeastern Five-lined Skink | © Ty Smith

Common Five-lined Skink | © Gray Catanzaro

Common Five-lined Skink | © Ty Smith

The same Common Five-lined Skink on different sides | © Ty Smith

Broadhead Skink | © Ty Smith

Common Five-lined Skink displaying types of lines | © Ty Smith

Dorsal Scale Counts

There is a way to ID these skinks with dorsal scale counts. First thing first, there are three lines you will need to know for this to work. The mid-dorsal line is that line down the center of the back. The lateral line goes over they eye and down the edges of the back. The Sublateral (as its name suggests) is the line below the lateral. This runs under the eye, through the ear, and over the legs. The photo on the left is there to display this.

Common Five-lined Skink | © Ty Smith

Southeastern Five-lined Skink | © Ty Smith

Common Five-lined Skinks will almost always have 3 scale rows between the mid-dorsal and lateral on their lower back, while Southeasterns will have four or sometimes five. Broadhead Skinks will often have three rows as well, but the line patterning is a little different.

Patterns

Below is an excerpt from my field journal. Let me be clear, this example is purely based on my observations and not backed up by any study I am aware of.

Common Five-lined Skink

Juvenile Common Five-lined Skink | © Ty Smith

Common Five-lined Skinks have pretty standard lines. On juvenile and female individuals where lines are visible, the mid-dorsal is a thick, and the other lines are similar in width (never exceeding the thickness of the mid-dorsal). All lines are the same color and fade evenly on all individuals, being a cream or golden color; usually taking up two-half scale rows. The lines on the face are the same color as the rest of the body, and the sublateral fades into the face pattern. On Commons, these lines thicken with age. Adult males are not too tricky either most of the time. Lines on male Common all fade at the same rate. I have never seen one that had any line or lines that stood out more than any other. Note: the amount of line visibility does vary from Skink to Skink, but all lines will be quite similar in size and color. The section of the sublateral that runs from the snout to ear is what we refer to as the subocular line. I mentioned this fades into the face pattern on female Commons, but it is not normally visible on breeding males. If they do retain this portion of the line, it is very faint. That said, it reappears on the same males when in their non-breeding colors. Male Common Five-lined Skinks retain several, random black scales. The other species rarely retain these, but scars can look similar at a distance. Females retain these too, but it is not as clear on them. The base color between the lateral and sublateral lines is often slightly or, sometimes, much darker than that between the lateral and mid-dorsal.

Southeastern Five-lined Skink

Juvenile Southeastern Five-lined Skink | © Ty Smith

We will make this very simple for females and juveniles. Their lines are very thin and clean. If you look at the lines in the area over the hips, you can compare them to that of the Common to get an ID. The mid dorsal on Southeasterns is rarely the widest line. On juveniles, these lines can seemingly fade out just before the tail, but are bright and orange on the head. Females retain a lot more of that black base color, while lines fade often to white. Sometimes, as the base color slowly turns gray, a black outline will be visible around the lines excluding the subocular. The subocular line does not fade into the face, and contrast a bit more than that of the Common. On females, the base color between the lateral and sublateral lines is often slightly darker than that between the lateral and mid-dorsal, with much more contrast on the males.

Males are very contrasting. They almost always retain the bright, white sublateral even on the face. Sometimes the lateral line will be retained, but the mid-dorsal tends to be much duller, and often will fade out completely during breeding. Their heads do not swell much during breeding like the other two do.

Broadhead Skink

Juvenile Broadhead Skink | © Ty Smith

A slight majority of juvenile Broadheads are going to make your life very simple, as they will have seven lines. These additional lines tend to run from the front to hind leg. The other lines are often much thicker than the Southeastern, yet not as uniform as the Common. Hatchlings tend to have richer line colors on their heads than the rest of their body. This fades quickly, but Broadheads feel overall more ornate than their cousins keeping brighter yellow lines, and light flecks on the hind legs. This species often hatches with coppery or rufous superlabials, and the facial line often wraps these instead of encompassing them. I will admit, that the Broadhead's variable line thickness means there is a short period of time when some individuals are very similar to Common Five-lined Skinks, and photos with poor detail can be impossible to distinguish. Their necks thicken, and their body starts to become more coppery with a little growth. This is when their lines start becoming paler. Quickly into this phase, one can start seeing a thick, dark outlining on their lines excluding the subocular. This subocular stays quite contrasting from the rest of the face. Eventually, the skink will develop a thick, fatty dewlap. Males have larger dewlaps, as these are to protect the neck from the jaws of other Broadheads.

Males often retain a much brighter, white sublateral, and a strong subocular line as well, until they are much older. These lines may fade completely on older males. Non-breeding males revert to that rich copper-color, and often display their lines again. The sublaterals are always the brightest and the mid-dorsal is the dullest.

Hatchling Common Five-lined Skink | © Ty Smith

Juvenile Common Five-lined Skink | © Ty Smith

Female Common Five-lined Skink | © Ty Smith

Old Female Common Five-lined Skink | © Ty Smith

Non-breeding Male Common Five-lined Skink | © Ty Smith

Breeding Male Common Five-lined Skink | © Ty Smith

Hatchling Southeastern Five-lined Skink | © Ty Smith

Juvenile Southeastern Five-lined Skink | © Ty Smith

Female Southeastern Five-lined Skink | © Ty Smith

Older Female Southeastern Five-lined Skink | © Ty Smith

Non-breeding Male Southeastern Five-lined Skink | © Ty Smith

Breeding Male Southeastern Five-lined Skink | © Ty Smith

Size Matters

Adult male Broadheads are beasts. Now, it seems Broadheads in NOVA are not as large as in the southeast, but the build is much different. I always liken it to a Chimpanzee and a Gorilla. They are both black, hairy apes, but the Gorilla is easy to ID from a silhouette because it is big and bulky. I have seen a male Broadhead Skink catch and eat a female Common Five-lined Skink. They are that big. Broadheads are so big, their juveniles will retain colors well pasted the size of an adult Common Five-lined Skink. I will say, in my full, honest opinion: the best way to distinguish male Broadhead Skinks from Common Five-lined Skinks without any feature is with size and build. That said, most people cannot properly judge size even at a distance of ten feet; but photos on bricks or other objects of known size should be easily identified without detailed pattern or scales.

Scaled silhouettes of a 12" Broadhead (left) and a 6" Common Five-lined Skink (right)

How about Range Maps?

As I mentioned earlier, I am currently looking through old records to clean up the range maps for the Southeastern Five-lined Skink. It seems this is a Coastal Plain and Southern Piedmont species, with a few exceptions. I found an individual in Bedford Co. and there is a good record from Shenandoah Co. on iNat. That said, looking at outlying VHS records, it seems these are almost all misidentifications including the Spotsylvania Co. record. So I can say on the adjacent map, green and orange counties are definitely good, and I have verified, while yellow needs to be evaluated and purple counties have no current records, but would fill in the gaps. If you would like to help us, feel free to contact us by email.

Common Five-lined Skinks are statewide. Nothing more to say... But Broadheads are a bit more patchy. They could be anywhere with proper habitat, excluding much of the Blue Ridge and Valley and Ridge, so I just recommend checking the map on the species profile.

Habitat

This is not exactly an ID technique, rather a way for you to know what to expect. Common Five-lined Skinks are not picky, living in old and new forest, meadows, and savannahs. Southeasterns like dry, sandy, and scrubby pine land or live oak forest. Broadheads are more at home in old growth oak forest, and cypress swamps. They are fairly arboreal, and require these huge trees for their happiness. In fact, it has been very difficult keeping Broadheads in captivity in my experience without using oak and cypress branches and bedding.

Wrapping it all Up

So, that is my overview. If you got anything out of this, I hope you realize that scale counts are pretty crummy. These species are different enough that we should be distinguishing them based off more then a what kind of scales run under the tail. There are many detail-focused herpers/herpetologist that have never learned how to identify these, because they are told they are identical and you have to count scales. This means when they find two identical specimens and all that is different is the scale counts, what ever species this is has now been misidentified.

I mentioned these misidentifications were harmful in the intro, but let me elaborate why. Say the Common Five-lined Skink started expanding due to its ability to thrive in human settlements, while Broadheads are being pushed out. We would almost certainly never know if the Broadhead's population was in danger or not if 30% of Commons are being misidentified as Broadheads. Say Southeastern Five-lined Skinks start declining drastically, and DWR allocates funding towards protecting this species on known sites. Well, if there are random records all over the state that have been misidentified, that spreads the money thin and gives too much to areas where the skink is never found. Now, I know the rebuttal to my examples is: "these species are stable". I do not disagree. All three species appear "stable", but I would argue that Broadheads in the south have and still are declining. I would not say they are rare or should be threatened, but we should keep an eye on these lizards. The lack of decline or the commonality of a species does not mean it will not need help eventually. The Passenger Pigeon should be the only example I need to give you... We can look at historical data to help us better understand changes. But historical data is only helpful if it is accurate. Let us start the trend of correcting the wrong on these beautiful lizards, and start getting our skinks right.

For papers, I have linked Reptile Database below so you can cruise the papers at your own leisure.

Reptile Database -- Common Five-lined Skink

Reptile Database -- Southeastern Five-lined Skink

Common Five-lined Skink Profile

Southeastern Five-lined Skink Profile

Reptile Database -- Broadhead Skink

Herp Review 53 (3) (Galveston Island Skink Paper)

Broadhead Skink Profile