Posted by:
RichardFHoyer
at Mon Sep 29 00:10:51 2003 [ Email Message ] [ Show All Posts by RichardFHoyer ]
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
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RE: Response to Contia questions - RichardFHoyer, Mon Sep 29 00:10:51 2003