Pipe snakes

(Cylindrophiidae)

Class Reptilia

Order Squamata

Suborder Serpentes

Family Cylindrophiidae

Thumbnail description
Small to moderate-sized, southeast Asian cylindrical-bodied snakes with ventral scales barely wider than the first dorsal scale row, short tails, and heads not demarcated from the trunk

Size
1–3 ft (0.4–1 m) total length

Number of genera, species
1 genus; 9 species

Habitat
Lowland forests, rice fields, but also urban areas; live predominately in leaf litter or loose soil and may be more common near water

Conservation status
Not classified by the IUCN

Distribution
Sri Lanka, Indonesia, Borneo, Myanmar, southern China, Thailand, Laos, Cambodia, Vietnam

Evolution and systematics

There are no fossils definitely assignable to this family and hence there is no evidence of its geological age. Molecular and morphological data suggest that cylindrophiids are distantly related to other basal alethinophidians (uropeltids, aniliids) as well as to basal macrostomatans. Current phylogenies place cylindrophiids near uropeltids and aniliids. No subfamilies are recognized.

Physical characteristics

Color patterns among the species vary, but most have a dark ground color (black or dark brown) with 40–60 yellow or red half-bands on the ventral surface that extend dorsally to different scale rows in different species. Some species have either longitudinal stripes (Cylindrophis lineatus) or a row of small light spots on either side of the dorsal midline (C. engkariensis). They differ from more basal alethinophidians (anomochilids and uropeltids) in having a fully toothed palate, using constriction to restrain prey, and in exploiting small vertebrates as prey. All species have a distinct mental groove in the lower jaw, no loreal or preocular scales (the prefrontals meet the supralabial scales), nostril located within a single nasal scale, 17–23 dorsal scale rows (most species have 19, 21, or 23; the most recently described species from Sarawak, Borneo, C. engkariensis, has 17 scale rows, the same number found in anomochilids), short tails (five to seven subcaudals), and a

spectacle covering a very small eye with a round or vertically subelliptical pupil. The skull is marked by relatively small numbers of robust teeth on the maxillae, dentaries, palatines, and pterygoids. There are no premaxillary teeth. A postorbital bone is present but typically floats in connective tissue and may be lost in many prepared skulls. The lower jaw has a highly mobile intramandibular joint but tight attachment between the tips of the mandibles.

Distribution

The distribution of the family is unusual. One species, C. maculatus, occurs in the lowlands of Sri Lanka. With the exception of C. ruffus, all of the other species occur on Indonesian islands and Borneo (shared by Indonesia and Malaysia). The rest of the range of the family is accounted for by C. ruffus, which is found from Myanmar east through southern China (including Hainan Island), Thailand, Laos, Cambodia, Vietnam, and south through the Malaysian peninsula, Sumatra, Borneo, Java, Sulawesi, Sula, and Buton. The most easterly distributed species is C. aruensis from Aru Island, south of Irian Jaya.

Habitat

These snakes inhabit lowland forests and rice fields, as well as urban areas. They live predominately in leaf litter or loose soil and may be more common near water. Specimens are often found after heavy rains.

Behavior

Very little is recorded of the behavior of most species of this family. One remarkable behavioral feature they have when threatened is to flatten the body and curl the tail backward over the trunk to expose bright red or yellow bands on the ventral tail. This display is often combined with continued movement of the tail and hiding the head under part of the trunk. Thus the hind part of the body gives the appearance of a small cobra in threatening display. If touched, the snakes may eject a fluid from the vent which seems to be a mixture of excretory and scent gland products. Captives usually cease this display within a few weeks. Observations on burrowing in captive C. ruffus show that these snakes are capable of burrowing quickly in loose soils and form tunnels approximately twice the cross sectional area of the body. When in the tunnel, snakes could move in either direction with nearly equal speed and were also capable of turning around in the tunnel and passing back along their own bodies. The feeding behavior of pipe snakes is unusual in that it depends on two distinct mechanisms for moving prey through the mouth. The initial swallowing is done by tiny movements of the upper jaws that also involve slight movements of the lower snout bones. Once the prey reaches the rear of the head, the snakes switch to a mechanism in which the anterior trunk compresses by tight curves of the vertebral column within the skin while the mouth is held closed. The mouth then opens and the vertebral column straightens, shooting the snake's head forward over the prey. This mechanism is very similar to one proposed for burrowing in uropeltids, and it is possible that cylindrophiids use this mechanism during burrowing (although it has not yet been reported).

Feeding ecology and diet

Most observations of feeding have been made in C. ruffus, but probably apply to the other species. Cylindrophiids appear to feed on a variety of small vertebrates, predominantly elongate vertebrates such as other snakes, elongate lizards, and eels. In captivity C. ruffus readily take small mice and fish. Prey are restrained or killed by constriction or crushed by the jaws.

Reproductive biology

Pipe snakes are viviparous, with the number of young correlated with the size of the mother. Litters tend to be small (two to three, possibly five) and the young are relatively large, approximately one-third to nearly one-half the length of the mother.

Conservation status

These snakes are not commonly encountered, and, like most fossorial groups, the status of their populations remains very poorly known. No species are listed by the IUCN.

Significance to humans

None known.

Resources

Books

Mattison, C. The Encyclopedia of Snakes. New York: Facts on File, 1995.

Zug, G. R., L. J. Vitt, and J. P. Caldwell. Herpetology: An Introductory Biology of Amphibians and Reptiles. 2nd ed. San Diego: Academic Press, 2001.

Periodicals

Cundall, D. "Feeding Behaviour in Cylindrophis and Its Bearing on the Evolution of Alethinophidian Snakes." Journal of Zoology (London) 237 (1995): 353–376.

Cundall, D., D. A. Rossman, and V. Wallach. "The Systematic Relationships of the Snake Genus Anomochilus." Zoological Journal of the Linnean Society 109 (1993): 275–299.

McDowell S. B., Jr. "A Catalogue of the Snakes of New Guinea and the Solomons, with Special Reference to Those in the Bernice P. Bishop Museum. Part 2, Anilioidea and Pythoninae." Journal of Herpetology 9 (1975): 1–79.

Steubing, R. "A New Species of Cylindrophis (Serpentes: Cylindrophiidae) from Sarawak, Western Borneo." Raffles Bulletin of Zoology 42 (1994): 967–973.

David Cundall, PhD