at Sun Jul 20 15:07:33 2008 [ Report Abuse ] [ Email Message ] [ Show All Posts by RichardFHoyer ]
Years ago on the Kingsnake classified forum, on occasion a Rubber Boas would be posted for sale. I haven't visited the classified forums for a number of years so do not know what is the current situation with respect to the availability of the species.
From my recent work with the species, there appears to be two reasonably distinct size morphs. The currently protected SRB from the San Bernardino and San Jacinto Mts. belong to what I characterize as the dwarf form of the species. But I discovered there are other populations of the dwarf morph that occur throughout S. Calif. from southern Tulare county (Kern Plateau) on south. However, I doubt if there is anyone in the business of breeding and selling the dwarf morph. So in that regard, purchasing a CB Southern Rubber Boa would seem to be of negligible concern.
As for you first question, there isn't any sure-fire way of being certain of the origin of any dwarf morph boa by use of morphological traits. Adults of most populations of the dwarf morph are generally light brown to tan dorsally, light yellow to cream yellow ventrally, have no mottling on the ventral surface, and the first 2 - 4 scale rows are yellow and not brown. All such populations generally have low ventral and maximum dorsal scale row counts.
As a population, the protected SRB in the San Bernardino Mts. tend to have a relatively flat suture separating the parietal and frontal head plates. But that trait varies in the SRB and specimens from other non-protected dwarf population can have similar relatively flat sutures. Also, a reasonably high percent of the San Bernardino SRBs have prenasal plates that are divided on one or both sides of the head, a trait that is uncommon in all other populations I have examined. However, because dwarf boas from non-protected populations can possess these same characteristics and some SRBs do not have relatively flat P/F sutures nor divided prenasals, there is no way to be certain as to the origin of any particular specimen.
Most members of the large morph of the species have higher maximum dorsal scale row and ventral counts but here again, there is overlap with boas from the dwarf populations including the SRBs. But since the maximum dorsal count of the SRB seem to be about 43 (possibly 44) and below, any boa having a maximum dorsal scale row count of 45 or more will not be the protected SRB.
At one time, coloration was considered a defining feature between the SRB and boa populations further north. But that is no longer the case. Other members of the dwarf form from Mt. Pinos, Breckenridge Mts., Scodie Mts., and southern Kern Plateau in Tulare county can be equally as light dorsally and ventrally as the SRBs in the San Bernardino Mts. And even members of the large morph, such as the boas from near Bishop, Calif. along the east slopes of the Sierras, are as light or lighter than the SRBs.
If adults boas are involved, then any male over 20 inches (stretched length) and female over 23 inches will not have originated from any of the dwarf populations. The rub of course is that CB boas are sold as juveniles which besides being small, are usually lighter in overall coloration than adults.
The one feature that has validity for identifying juveniles as belonging to the dwarf or large morph is that of length. If a new born CB (or wild) boa is over 9 inches in stretched length, then in all probability it originated from large morph parent stock. Of the dwarf morph litters I have examined, the largest neonates were either 8 3/4 or 8 7/8 inches, stretched length.
Richard F. Hoyer
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