Reptile & Amphibian Forums

RS Newton:

Re question #1: The species are sympatric in some regions in the broad sense as their distributions overlap although they are found in somewhat different habitats. I feel it is only a matter of time before the two forms will be found either just a few meters away or possibly under the same cover object.

In the Santa Cruz Mts., both species occur along Skyline Road. (Highway #35) that separates Santa Cruz and Santa Clara Counties.
I found two specimen of the Forest Sharp-tailed Snake east of Highway 35 along highway #9 in Santa Clara County just 4-5 miles west of the Saratoga City limits. From CAS records, preserved specimens of both species were collected from the Stanford Univsity campus. In Oregon, the Forest Sharptail occurs east and west of the I-5 corridor whereas the Common Sharp-tailed Snake (Contia tenuis)has been documented at several localities along the I-5 corridor.

Question #2: It will be up to others to try and define, in more specific terms, the differences in habitat preferences between the two species. In general terms, Contia tenuis is found in drier, more open habitat than the Forest Sharp-tailed Snake which for the most part, occurs in or near forested habitits. However, I have collected the new form near the coast of N. Calif. (Carlotta, Calif. Humboldt County) in open, grassland, scrub habitat.

Contia tenuis is found at or near the coast in Monterey, Marin, and Sonoma Counties (and probably San Luis Obispo Co.) whereas the Forest Sharptail is found near the coast in Santa Cruz, possibly San Mateo, Mendocino, and Humboldt Counties in Calif. and Curry County in Oregon. It is quite probable that it occurs at or near the coast in Del Norte Co., Calif and Coos County, Ore. as well. It is known from the interior of Coos Co. and a voucher specimen has yet to be obtained from Del Norte Co. If one understands and accepts the concept of habitat association as I do, then the species clearly exist in Del Norte County and it is just a matter of time before the species is documented from that county. A few years ago, I met a (conservation) biologist that discounts such associations indicating a species cannot be said to occur in such and such a place until the time it is found there.

Questions #3: Any meaningful speculation is beyond my abilities with respect to reproductive isolation between the species. Except for documenting new locality records for both species, I have essentially terminated my field and laboratory efforts as of the end of Feb. 2002 and have returned to my main interest, Charina bottae.

For awhile, I was maintaining 10-12 specimens of both species (separately). I no longer maintain any Contia tenuis. I still maintain the original female Forest Shart-tailed Snake I found in July 1998 in Mendocino County, Calif. plus one male and two other females found in the same region in 1999. I have observed only one courtship and coupling event in the new species but did not get eggs. Never observed courtship or coupling in C. tenuis and all data on Contia tenuis reproduction came from eggs obtained from captured females.

These species are not too difficult to maintain but one has to be diligent in collecting prey and that take a great deal of time and effort. Also, I am limited in the types of space and cages/aquaria needed to adequately investigate these snakes in a meaningful manner. All my efforts are unfunded and as mentioned above, I am not devoting my time and efforts to my primary interest, the Rubber Boa.

Question #4: I discovered at least one function of the pointed spine of Contia tenuis (in about 1970) verbally reporting my observations to herpetologist Dr. Robert Storm and others in the zoology dept. at OSU along with a written note to Dr. Robert Stebbins. When these snakes grasp a slug that tries to escape, they will anchor themselves with their spine either in any nearby object or vertically by poking the spine in the substrate.

The Forest Sharp-tailed Snake also has the spine at the tip of the tail. They also will use the tail and lower body in a similar fashion. Like the Northwestern Garter Snake, they will use their prehensile like tail to wrap around any object as an anchor or to pull backwards. Clearly, more refined observations are needed in this regard.

From self-made herpetologist, Alan St. John of Bend, Oregon (who just published 'Reptiles of the Northwest'--Lone Pine Pub. Co.) I learned a simple technique to observe how Contia tenuis uses its spine that confirms my observations about the species using it as an anchor. He mentioned taking a pillow case and sliding a Sharptail down at an angle (I have duplicated this) and often the specimen will try and anchor itself with its spine while sliding down the incline.

But as to the reason for the difference in tail length, I suspect there may be a difference in the frequecny of various prey each species encounters due to the difference in habitat preference. Regardless of what some publications have mentioned indicating that C. tenuis strictly preys on slugs (didn't make sense biologically) I have found that both species prey on slender salamanders and worms as well. Living in somewhat damper habitats, perhaps the longer tail of the Forest Sharptail is advantagous for the prey it encounters. My lack of background in formal herpetological training and related literature doesn't allow me to make reasoned 'educated' guesses in this regard.

Question #5: Again, this type of speculation is out of my league. In Oct. 1999 when I showed specimens of each form to Robert Stebbins, that was his first thought, what was the ancestral type and what agents, geological events, etc. caused separation, etc.

The story of Contia may unfold yet another facet. In my examination of all preserved material I could lay my hands on, the 7 specimens from the southern extreme of the species range in Sequoia Nat. Park, Tulare Co., Calif. established the upper limits for C. tenuis of both relative tail length and caudal counts. Despite preservation, coloration seemed slightly different. There is now some evidence that these high elevation Sharp-tailed Snakes may represent yet an other form (subspecies, subclade) of C. tenuis.

Richard F. Hoyer

Thanks for a most thoughtful and informative reply. It appears that both species have coexisted for a long period of time, judging by their distribution.

It appears that the ranges of the two species are still being reexamined. Which of the two species is the more widespread?

I am thinking that perhaps the long tail of the forest species, according to your description of how Contia species use their tails, may be advantageous in the forest substrate owing to the amount of leaf litter and the looseness of the soil. Perhaps the long tail allows the forest species to anchor itself better by reaching beyond the loose surface cover into a firmer substrate. For the species living in a drier habitat, a long tail may not be as useful as a more muscular but shorter one.

Given its diet of organisms that require a moist environment, perhaps Contia originated in a forested setting, and the short tail is an adaptation for a drier habitat with a firmer ground surface that in turn requires more muscle but not necessarily a longer tail to anchor. If my hypothesis is correct, then the long tailed form would most likely be the ancestral form. It would be most interesting to find out whether they meet and whether they interbreed with one another.

RS:
Besides the question of ancestral type, what geological events isolated these two forum long enough so that when conditions returned so that their distributions became parapatric and probably sympatric, that they had diverged to the point that they no longer interbreed(or so it seems)?

Of the several hundred preserved specimens examined and over 1700
lives specimens (mostly from Oregon) I have examined, none exhibited intermediate traits. The closest that such an situation exists is in the 7 preserved specimens from high elevation in Tulare County. Three additional specimens of the Tulare population were found in 2002 with one being examined after it had been preserved and two live specimens (which I have since donated to CAS). This population resides in habitat very similar to the Forest Sharp-tailed Snake and also exhibits a relatively long tail and high caudal count. However, the range of both traits overlap C. tenuis and not the Forest Sharp-tailed Snake.

Recent mtDNA results show that this Tulare population does diverge considerably from C. tenuis but not like the divergence shown by the Forest Sharp-tailed Snake. So there appears to be a connection between forested habitats and longer tails/higher caudal counts.

There were about 65 - 75 preserved specimens of the Forest Sharp-tailed Snake in all collections which provided a base upon which to identify a reasonably amount of its distribution. With the bulk of preserved specimens being C. tenuis, its distribution is far better identified.

From habitat association, I would expect the Forest Sharp-tail to eventually be found in the coniferous forests in Marin County and through much of Del Norte County in Calif. It has only been identified from three Oregon counties of Curry, Coos, and Douglas. But considering habitat association, I expect it will eventually be found in Jackson, Josephine, and Lane Counties. It may possibly exist further north in the coniferous forested habitats of Benton, perhaps Lincoln counties on the west side of the Willamette Valley and perhaps Linn County on the east side of that valley.

The Common Sharptail (C. tenuis) is far more widespread occurring on some of the islands in Puget Sound and SW corner of Vancouver Island, in the Tacoma region of W. Wash., in eastern Washington due east of Seattle, and along the Columbia River from at least Lyle, Wash. opposite The Dalles, Oregon to Carson, Wash. west of Hood River, Oregon. I would not be surprised that the species may eventually be found is suitable habitat south of Tacoma all the way down to Vancouver, Wash.

In Oregon it has been documented in Wasco County east of Mt. Hood and in all interior counties from Yamhill south to the Calif. border. I am certain it will eventually be found in other counties as well. When I began my study, Contia (both species)had been documented from 8 counties and I increased that number to 11. The species is so obscure that most biologists have never heard of it let alone be able to identify the species. There has been one full article published on the species (Cook, 1960). In Calif. C. tenuis has a fairly large distribution from San Luis Obispo County northward on the coastal side and Tulare County northward on the western side of the Sierra plus a number of interior counties.

Concerning the subject of interbreeding, the two size morphs of Charina bottae readily cross. What mechanism has kept one morph from overwhelming the other (where they meet) is another great question for speculation. I have one idea in that regard.

I have completed a couple of crosses between dwarf male X large morph females. I currently have two surviving offspring from one of those crosses and both (one male and one female) are now adults. In the next year or so, I plan on making the reciprocal cross of dwarf female X large morph male. Will also backcross the hybrid female X dwarf male and hybrid male X dwarf female.

Richard F. Hoyer

The distribution of Contia tenuis on islands suggest to me that this species got there during an ice age, when sea levels are lower, temperatures are cooler and the islands are connected to the mainland. The climate is also drier during an ice age. Areas that once presented barriers to dispersal are no longer too hot to cross. High altitude species are forced to retreat to the lowland areas. As the ice sheet advances, many populations of the forest species are forced to move into lowland areas. Because of cooler temperatures, some of these populations are able to move into grassland habitats. The short-tailed form could have evolved in such a setting. Once it evolved, it is able to disperse widely because of favorable conditions. As the ice age ends, the grassland adapted species is forced to move into slightly cooler habitats, such as woodlands. The long tailed or forest form is in turn forced to retreat into more heavily forested areas in higher elevations. The different habitat requirements of the two forms may be keeping them apart. It may have taken more than one ice age episode for the two species to have dispersed to their respective ranges or it could have happened within the last ice age. It would be interesting to see if there are areas that are suitable habitats for both forms and to find out if they will or will not interbreed in nature.

Concerning Charina bottae, it appears from the mtDNA data that this species made 2 rather rapid northward expansions (one along the coast and one along the Sierrae Nevada mountains) of its range from the south once the barriers to dispersal disappeared. The large morphs evolved during the northward expansions. The 2 large morphs appear to be independently derived from different populations of the ancestral dwarf form, one in eastern Kern/southern Tulare Counties and one in western Kern County. The large morphs may simply be better adapted to the northern parts of their ranges, as their independent derivations suggest. Once the large morphs evolved, any small morph boas that had moved north at the same time is probably at an disadvantage. Either the small morph became extinct from competition, or the two interbred freely and the large morph is the dominant phenotype in these crosses. Natural selection appears to have favored the large morphs in the northern parts of the range of Charina bottae. The small morph may be persisting in the south because it is isolated from the large morph. The San Bernardino County population is isolated. The western Kern County small morph population is also isolated from the northwestern large morph population by stretches of unoccupied habitat (Santa Monica and San Gabriel Mountains for example). The situation in eastern Kern and southern Tulare Counties appears more complicated. Perhaps different habitat preferences or geological barriers have prevented the large morph from a southward reverse migration. Since I am not familiar with the geography of this area, I am unable to speculate on the factors which may allow the small morph to persist in this area. Perhaps the large morphs are successful because their larger bodies help them conserve water better (a smaller surface to volume ratio), allowing them to occupy drier habitats than the southern form. A larger body also takes longer to warm (again because of the smaller surface to volume ratio), making it unsuitable for more heavily shaded forest habitats.

RS:
Simply from examining the distributions of the two Contia species, one can surmise difference in habitat requirements. It is another thing to try and pinpoint what those exact requirments may be as you can find what appears to be typical Forest Sharptail habitat gradually transform into typical Common Sharptail habitat all within a dozen meters or thereabout.

As an example, highway 9 winds uphill from the west city limits of Saratoga, Calif. (Santa Clara Co.) about 5 - 6 miles to the summit or spine of the Santa Cruz Mts. that may be about 900 to 1000 ft. elevation where highway 9 intersect highway 35 or Skyline Blvd. Skyline runs north and south long the spine of those mts. and separates Santa Clara county on the east with Santa Cruz county on the west side of that road. There are virtually little to no shoulders along highway 9 with the south side hugging the hillside and covered with trees which thus shades that side of the road. At various points, the north side of the highway is more exposed to the sun and more open brush / grassland habitat occurs at spots along that side of the road and across the ravine and hillside to the north. In those open, grassy areas along the north side of highway 9 and only 50 - 80 meters across the ravine in places with open grassland/scrub habitat, I would expect to find the Common Sharptail (C. tenuis).

In May 2000, I collected two Forest Sharptails along the shaded south side. Across the road over the guard rail under small pieces of junk in the grass habitat I found Ringneck and garter snakes. The road is two lanes. I would put big money that C. tenuis occurs in the open areas just north of that road.

Along highway 35 at 0.5 miles south of the junction with highway 9, I also found a Forest Sharptail at the base of a small cliff under leaf litter. This area was far more open than where I found the two specimens along highway 9. And again, about 50 meters or less south is typical C. tenius habitat.
About 8 - 9 miles south along highway 35 my son Ryan did find C. tenuis on the same side (east) of the road as I found the Forest Sharptail but his habitat was open grass/brush.

I suspect that one would need to obtain and chart specific factors of rainfall, humidity, cloud cover, etc. and compare that with known locality sightings of the two species to possibly characterize habitat requirments. Even then, there probably would be some overlap. Possibly there is a difference between the species for mean temperatures and minimum days at certain temperatures at which eggs will hatch. The Forest Sharptail eggs can possibly hatch successful at lower number and/or with days at certain minimum temperatures than C. tenuis.

Richard F. Hoyer

RS:
The geography in S. Calif., and what I have discovered the past 5-6 years about the distribution of the two size morphs of C. bottae in that region follows:

The N. Fork, Kern River originates in the westerm Sierras and travels due south through a wide canyon into Kern County entering a small (Kern R.) valley at Kernville at about 2700 ft. elevation. A dam at the southwest corner of the valley creates a reservoir and the town of Lake Isabella is positioned at the south end of the lake. The Kern River then turns west towards Bakersfield going through a deep gorge.

The Kern River valley extends about 25-30 miles east from Lake Isabella. The S. Fork Kern River also flows south through the east-central Sierras entering near the east end of the Kern R. Valley then turning west to eventually flow into the reservoir.

The continuous high to moderate (4500 ft. ) elevations of the Sierra Nevada terminate at two points in the south. The southwestern arm of the Sierras west of the Kern Valley and K.R. Valley are known as the Greenhorn Mts and end at the point were the Kern River heads west towards Bakersfield through the deep, narrow Kern R. gorge. Immediately south of the Greenhorns across this gorge is Breckenridge Mt., about 30 miles due east of Bakersfield.

East of the N.F. Kern River canyon, the Sierras are known as the Kern Plateau which extends about 45-60 miles eastward. The southern boundry of the Kern Plateau is the central and eastern portions of the Kern River Valley. The far east end of the Kern Plateau ends at the Mojave Desert.

Due south of the Kern Plateau across the K.R. Valley are the Piute Mts. and Scodie Mts. Low elevation desert or near desert habitats separate Breckenridge Mt. from the Piutes immediately to the east and the Scodie Mts immediately east of the Piutes.

At the east end of the Kern River Valley is Walker Pass that at around 5200 ft. separates the Kern Plateau from the Scodie Mts. Just east of Walker Pass and and virtually surrounding the Scodie Mts. is the Mojave Desert. Being adjacent to the Mojave Desert immediately to the east, Walker Pass itself exists in an arid situation dominated by a Pinion Pine forest. One can speculate that a C. bottae population could exist in the vicinity of that pass particularly on the lower north slopes of the Scodie Mts. However, the habitat appears to be more suitable for the Rosy Boa rather than the Rubber Boa. The Rosy Boa has been documented on both sides of that pass.

Suitable Rubber Boa habitat exists unbroken from the Greenhorn Mts. and Kern Plateau all the way to British Columbia. South of the Greenhorn Mts. and Kern Plateau, the Rubber Boa exists on isolated mt. peaks and mountain ranges.

Samples of live and preserved boa are large enough to assert that the dwarf form occurs in the San Bernardino Mts., Tehachapi Mts., Mt. Pinos, and Breckenridge Mt. all south of the Kern Plateau and Greenhorn Mts. From geographic inference, the dwarf form should occur in the San Jacinto Mts. in Riverside Co. due south of the San Bernardino Mts. Likewise, dwarf populations should exist in suitable habitat in the various peaks near Mt. Pinos in Ventura and southwestern Kern Counties east of the I-5 corridor south of Bakersfield towards L.A. C. bottae has never been documented in the San Gabriel Mts. of L.A. County and extreme western San Bernardino county, about a 60 mile gap between the population in the San Beranardino mts. and populations that occur in the greater Mt. Pinos region to the west.

Fragmentary evidence indicates the dwarf form also exists in the isolated Piutes and Scodie Mts. south of the Kern Plateau. But reasonably solid evidence also indicates the dwarf morph exists in the southern Greenhorn Mts. at least from Alta Sierra south. Similar evidence indicates the dwarf morph occurs in the Kern Plateau from near the S. Fork of the Kern River 5-7 miles west into the Fish Creek drainage. It undoubtedly exists some unknown distances south, west and possibly east of the above regions and how far north is anybodies guess.

There are two preserved specimens from just south of Alta Sierra and both appear to be of the dwarf form. Some live specimens from south of Alta Sierra support the dwarf scenario in that area. From Alta Sierra, there exists a gap of about 30-40 miles north into Tulare County where preserved specimens are lacking. Preserved specimens from Sequoia Nat. Park 30 - 40 miles north of Alta Sierra belong to the large morph of C. bottae.

In the past couple of years, I have recorded data (and took tissue samples) from about 19 - 20 live specimens found a few miles west and southwest of Johnsondale, Calif. in about the center of this 30-40 mile gap between suspected dwarf population to the south and the known large morph population to the north.

Low ventral and max. dorsal counts are concordant with the dwarf form. Much higher ventral and mid dorsal scale counts are concordant with the large morph from the region of Sequoia Nat. Park in Tulare County northward to about southern Plumas County,
Calif. in the central Sierras. The combination of length and scales counts amongst the 19 or 20 boas examined in the gap between size morphs suggest that this region is where the two morphs intergrade. I have no idea as to where these two forms might meet on the Kern Plateau.

From the information obtained from captives and the mix of traits found in the group of boas examined west/southwest of Johnsondale, it is my position that there is nothing preventing the two forms from interbreeding freely. It remains to be seen what mechanism has prevented the large morph from overwhelming its smaller cousin in the southern Greenhorns and Kern Plateau (or the reverse situation).

Concerning habitat perhaps affecting distribution, at this point that does not seem to fit existing observations. Both morphs occur in or near dense coniferous forests, open coniferous forests, and in arid type habitats bordering on desert. For instance, the dwarf populations at the east end of the San Bernadino Mts., in the Scodie Mts. and on the Kern Plateau occur in Pinion Pine, Juniper, sagebrush, grassland type habitats with cactus occurring in boa habitat in the latter two regions.

The large morph occurs in similar Pinion Pine, sagebrush, grassland habitat with cactus on the east side of the Sierras southwest, west, and northwest of Bishop, Calif. In Oregon the large morph has been documented in W. Juniper, sagebrush and grassland habitats and in fact, my only E. Oregon research site is stricly sagebrush/grassland habitat with no free water within 25-35 miles in any direction.

If you have a map of Calif., the above geographical description and occurrence of both morphs would be better visualized. If the dwarf form only existed in the isolated peaks and mountains of S. Calif., that would present a much tidier picture than the present situation in which the dwarf form occurs in two regions of the southern Sierra Nevada Mts. and the two size morphs appear to intergrade in one known region.

Hope this provides you with a better idea of the geography and distribution of C. bottae in S. Calif.

Richard F. Hoyer