Sunday, July 7, 2013

Sharp-Tailed Snake : Long or Short?

Sharp-tailed snake showing the black-white crossbars underneath and spine on the tip of its tail.  
Do you ever just flip through a field guide? Besides enjoying the gorgeous illustrations such as Stebbins' plates in Western Reptiles and Amphibians, I sometimes randomly open a field guide and start reading. I know I will either learn an interesting fact or hear a good story from a raconteur like Alan St. John in Reptiles of the Northwest. And I might remember an important fieldmark for the next time I have only a few seconds to identify a surprise visitor.

Recognizing a distinct black-white pattern helped me respond quickly to a little snake that appeared in the yard in April. Was this the newly described forest sharp-tailed snake? I immediately abandoned my yardwork and spent the rest of the afternoon playing citizen scientist.

The darn gophers like to tunnel along the low concrete wall in the front yard near my favorite birdbath. It's a gorgeous birdbath with a base shaped like overlapping lily leaves. I specifically placed that birdbath at that location in the front yard so I could watch the birds from the kitchen window while I cook and wash dishes. The gopher digging causes the birdbath to tip and spill its water, and eventually fall over. Someday, I'm afraid those gophers are going to break my favorite birdbath.

I was vengefully caving in the gopher tunnels underneath the birdbath in April when a small snake flipped out of the ground. I paused, quickly ran the brown/red color through my memory banks, dropped the shovel, and snatched up the snake. As I hoped, when I turned the drab captive over, it had a distinct belly side.

The black ladder pattern underneath the sharp-tailed snake stands out.   
The first time I saw that black ladder pattern under a snake was in June 2008. A dim light went off, probably a result of previously flipping through a field guide. It was enough to make me interrupt my inspection of the water tank and carry the snake to the house to identify it as a sharp-tailed snake. When I was satisfied I had found a new life species, I took a few photos, put the snake back, and returned to worrying about the water tank.

Since then, I've read that two species of sharp-tailed snakes are now recognized: the common sharp-tailed snake (Contia tenuis) and the forest sharp-tailed snake (Contia longicaudae). They look very similar but the later has a longer tail and is mostly found in coastal areas of California and Oregon.

One of the three locations where these two species occur in proximity to each other is San Mateo County of the Santa Cruz Mountains.

That's the location of the Dipper Ranch.

It's not clear if the range of the two species overlap, but they appear to prefer different habitats. Forest sharp-tailed snakes have been found in moist well-forested areas; common sharp-tailed snakes have been found in more dry and open grasslands, mixed woodland and chaparral.

The Dipper Ranch has both of these habitat types.

Dipper Ranch in foreground has a mix of open grasslands, forested drainages and canyons and even some brushy slopes. Long Ridge in the background is mostly covered by continuous forest.  
Located just west of and 500 feet lower in elevation than the north-south ridgeline which extends down the length of the Santa Cruz Mountains, the Dipper Ranch is influenced by moist air that sweeps off the Pacific Ocean and swirls across the uneven topography creating a complicated patchwork of vegetation - a lot of edge makes for more diverse ecology. Like dark green hands, moist forests of Douglas fir and coast redwood cloak the drainages and the steep narrow canyons, while the less steep slopes are covered with wide sweeps of summer-brown grasslands and pebbled by olivaceous stands of mixed oaks.

If I carefully document the traits of each sharp-tailed snake I find on the Dipper Ranch to identify it to species, and if I note the geographic location and habitat type of each find, I might help further define the range of the two species in this part of the state.

Sounds like nerdy fun to me.

The orange-brown stripes on the upper sides of this sharp-tailed snake (2013) were bright.
Girls who handle snakes often have barbwire cuts on their fingers, dirt rubbed into their palms, and snaggy fingernails - that's just how we are.  
Except I've only found three sharpies on the ranch so far and I was ignorant of these scaly facts for the first two. With this third individual dangling in my hand in April, I now had the chance to further investigate. I walked into the house to show my friend visiting from Florida. She's a biologist too, so she's used to people walking around with snakes. We made the sharpie comfortable in a tightly-latched terrarium while I pulled out my references.

To positively distinguish the two species of sharp-tailed snakes, you need to compare the total length of the snake to the tail length, count the number of scales on the underside of the tail, and measure in millimeters the width of the narrow black band versus white background on the belly scales (Feldman and Hoyer, 2010). This requires careful handling of the snake in order to get accurate counts and measurements. And to be nice to the snake. Between us two girls, the length measurements went smoothly but it was too hard to count the tiny scales or measure the black/white scale proportions on a squiggly live specimen, so I took numerous photos of the gently-held snake to look at more closely later.

Sharp-tailed snakes may use the sharp spine at the tip of the tail to wedge themselves into the substrate while tugging out stubborn slugs for dinner.  
The April sharpie had a total length of 190 mm and tail length of 35 mm. That gave it a relative tail length of 18.42% which is in the range of both male (17.27 to 22.38%) and female (15.38 to 19.82%) forest sharp-tailed snakes, but just barely above the range for the male common sharp-tailed snake (12.43 to 18.29%) for the hundreds of specimens examined by Feldman and Hoyer. Because this particular individual had bright colors, I was guessing it was a juvenile, meaning its proportions may still be adjusting. Therefore it was important to confirm the species ID with the scale count which doesn't change as a snake ages.

It wasn't until the next day that I had the time to enlarge the photos on the screen of my laptop and count the tiny tail scales. I was in a managers' meeting. After recounting numerous times, I determined there were either 47 or 48 tail scales. Checking Table 1 in the Feldman and Hoyer paper, that squarely put the April sharpie in the range of forest sharp-tailed snakes and outside the range of common sharp-tailed snakes, and it was also probably a female. I'm sure I probably uttered a little whoop in that meeting and it wasn't about the accounting software that was on the agenda. The rangers are used to ignoring me but I noticed the eyebrows of the Undercover Naturalist pop up.

Caudal (tail) scales are to the right of the thumbnail indicator. The more anterior caudal scales do have some black blotches but they are not continuous bands across the entire width of the scale as with the ventral scales to the left.  
I had the April Contia with me in the office that day because I wanted to show it to the Undercover Naturalist. It is the wish of all biologists worldwide who are struggling with balky accounting software to be interrupted with a new snake species. It's in my job description to keep senior biologists happy, so after the meeting, I walked the terrarium down to the corner office. The visit was much appreciated.

And it gave me a chance to talk about a few things about the snake that were not quite lining up. Based on measurements I took off my photos, the width of the black bands on the April sharpie were 40 to 50% of the belly scales. Some of the lit says forest sharp-tailed snakes have black bands one-fourth to one-third of each scale whereas common sharp-tailed snakes have thicker black ladder rungs underneath, one-third to one-half. Maybe my photos were too blurry to get a good measurement of this tiny feature. The Undercover Naturalist recommended it was time for me to finally get that macro lens. Feldman and Hoyer state that the black bands are usually absent from the tail scales of the forest long-tailed snake. The April sharpie showed black blotches on the tail scales but not continuous bands. What did that mean? I looked at photos on Cal-Herps of both species but just couldn't figure that feature out.

Also, I wasn't sure the distinct species habitat preferences described in the literature matched the conditions on the Dipper ground. The Dipper yard is mostly open grassland and dry in the summer although one side is lined by several large native big-leaf maple trees which surely predate the house. The Undercover Naturalist suggested I check my field notes and photos from the previous two Contias I found on the ranch. Even though I did not take any measurements for those snakes, maybe I could find some clues.

I found the first sharpie by the watertank on June 8, 2008.

Handsome specimen for my first sharp-tailed snake June 8, 2008.  
Although I didn't take any measurements in 2008, you can see the vent (dark line) in the lower part of the photo and the relatively long length of the tail after it.  
We found the second sharp-tailed snake on a dirt road near the Newt Pond at dusk on August 7, 2011.

I didn't take any measurements of this snake in 2011 and this is the only photo I took. I remember it as being small and lightly colored.  
All three finds were within 1/4 mile of each other and occurred in open areas adjacent to mixed oak forests. Studying my field notes, I also realized that they all occurred near water: the dripping water tank, a seasonal pond, and a gopher-tilting birdbath that constantly spills. Even though the habitat of all three of these sharpies was a better match for the common sharp-tailed snake, was the special moisture conditions at each of these locations enough to support the forest sharp-tailed snake?

The Dipper farmyard where the April sharp-tailed snake was found is mostly open country although oak forests are close by. It is moist in the winter wet season and dry in the summer.  
On the way home from the office with the April Contia, I stopped at the Alpine Inn to meet some of my co-workers. While parking, I decided it was much too hot to leave the little snake in the car, so I tucked the terrarium in a bag and brought it into the modest roadhouse. Gathered around an outside picnic table, I couldn't resist pulling out the little snake to alert my co-workers to fieldmarks they should check if they ever find a sharp-tailed snake in the Santa Cruz Mountains. Somewhere out there is a motorcyclist who saw his first and probably only sharp-tail snake in a beer garden in Portola Valley. I hope he never forgets it. Maybe he will get a tattoo of the sharp-tailed snake but will he pick the short one or the long one? For now, I am tentatively identifying the April Contia as a forest sharp-tailed snake. I look forward to finding more sharp-tailed snakes and measuring and counting their tiny scales before I return them to their edgy habitat.

common sharp-tailed snakeContia tenuis
forest sharp-tailed snake, Contia longicaudae

See also:

  • Robert C. Stebbins, Western Reptiles and Amphibians, Peterson Field Guide, 3rd edition, 2003.
  • Alan St. John, Reptiles of the Northwest, Lone Pine Publishing, 2002.
  • Chris R. Feldman and Richard F. Hoyer, A New Species of Snake in the Genus Contia (Squamata: Colubridae) from California and Oregon, Copeia 2010, No. 2, 254-267.
  • California Herps


  1. This is SO cool. And yep, I had to count the caudal scales in that photo. Thanks for your wonderful posts!

  2. I have been interested in the common sharp-tailed snake, ever since I found my first one here on my farm outside of Grass Valley. They are not easy to spot, as their brown, putty color blend in too well with our type of dirt. However, my Maine Coon did bring me my longest specimen yet. She brought one into the house & let it loose on my wood floors. Best I could tell without measuring, it was nearly 2 1/2 ft long! She was scolded, & I returned it to my property (and the cat was left inside while I did so :)


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