Oreocryptophis porphyraceus (= Elaphe porphyracea) is a snake species characterized by a highly variable colour pattern which plays a key role in its sub-specific taxonomy. There are two subspecies groups differentiated by their distinctly different pattern.
The O. porphyraceus-group has dark stripes restricted to the posterior part of the body, or alternatively stripes are completely absent, while the O. nigrofasciatus group has stripes covering the entire body (Schulz & Helfenberger, 1998).
The subspecies Oreocryptophis porphyraceus coxi, which is assigned to the O. nigrofasciatus group, is diagnosed by the possession of stripes which are up to 2 dorsals wide. These stripes may be accompanied by 1 or 2 dark blotches on the anterior part of the body.
On 5 August 2006, a juvenile female with aberrant pattern hatched from a clutch of 4 eggs laid by a O. p. coxi F2 captive-bred female (origin: Thailand, Loei province) after incubation on wet vermiculite at 27-28ºC. This juvenile had no dark blotches and stripes were absent on the anterior third of the body. Although two dark dorsolateral stripes were slightly visible on the middle part of the body, they were normally developed on the posterior part of the body and on the tail. The head pattern was normal, with two dorsolateral stripes abruptly terminating in the neck region. Normally coloured female specimens hatched from two other eggs of the same clutch while the remaining egg contained a normally-patterned dead prodichotomic (two-headed) embryo. The specimen with the aberrant pattern is still being kept alive and after 18 months its colouration has become less contrasted, although the pattern itself has not undergone any change.
Stripes are common in snakes´ colour pattern, and they are believed to be related to the avoidance of predators (Shine, 1991). The striped pattern and uniform colouration create the illusion of immobility when the snake is moving forward (Bittner, 2003). Compared to the uniformly coloured snake, this illusion may be enhanced in a striped snake as its body looks narrower. Stripes also function disruptively making the pattern more cryptic (Jackson et al., 1976). This could confer a selective advantage in comparison to conspicuous uniformly coloured O. p. coxi specimens and could explain why no wild specimens with reduced pattern have been found so far. The pattern reduction observed in the juvenile may be caused by inbreeding under human care, although the taxon has not been subjected to multi-generational selective breeding. Another possible explanation is epigenetic, where the pattern may represent an example of phenotypic plasticity influenced by artificial incubation.
Figure 1. The freshly hatched Oreocryptophis porphyraceus coxi showing the pattern reduction on the anterior part of the body.
Bittner, T.D. (2003). Polymorphic clay models of Thamnophis sirtalis suggest patterns of avian predation. Ohio J. Sci. 103, 62-66.
Jackson, J.F. (1976). Dorsal pigmentation pattern of snakes as an anti-predator strategy – multivariate approach. Am. Nat. 110, 1029-1053.
Schulz, K.-D. & Helfenberger, N. (1998). Eine Revision des Unterarten-Komplexes der Roten Bambusnatter Elaphe porphyracea (Cantor, 1839). Sauria, 20, 1, 25-45.
Shine, R. (1991). Australian Snakes: a natural history. Chatswood: Reed Books. 223 pp.
Number 107 - Herpetological Bulletin  British Herpetological Society