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Shieldtail Snakes (Uropeltidae)

Shieldtail snakes

(Uropeltidae)

Class Reptilia

Order Squamata

Suborder Serpentes

Family Uropeltidae


Thumbnail description
Small, cylindrical, smooth-scaled snakes; many species have conical, pointed heads smaller than the anterior trunk and a blunt or even an obliquely flattened tail covered with one or more enlarged scales decorated with keels or spines

Size
7–23 in (18–58 cm) total length

Number of genera, species
8 genera; 47 species

Habitat
Moist soils of lowland and upland forests, under logs and loose cover, and among roots of trees and shrubs; many species occur in relatively compacted clay soils in which they actively burrow

Conservation status
Not classified by IUCN

Distribution
Sri Lanka and southern India

Evolution and systematics

No fossil uropeltids are known. Their current distribution suggests a relict pattern except that their phylogenetic relationships appear to be with the most basal of living alethinophidian ("true," or large-jawed) snakes. Both molecular and morphological features support affinity with cylindrophiids. No subfamilies are recognized.

Physical characteristics

Uropeltids display a surprising diversity of external features despite their superficial resemblance. All are relatively small snakes, most having adult sizes below 12 in (30 cm) total length. A few species (e.g., Rhinophis oxyrhynchus, Uropeltis ocellatus) attain sizes nearly twice this length. In all uropeltids the eye is covered by an ocular shield with no separate spectacle. Instead, the region of the ocular shield overlying the eye is transparent. In species other than Platyplectrurus, the head tapers from a wider anterior trunk, and the snout is flattened either horizontally (dorsoventrally), as in Melanophidium and Platyplectrurus, or vertically (mediolaterally), as in most species of Rhinophis. Species with pointed snouts have modified rostral scales with thickened keratinized layers. In Rhinophis, one of the largest members of the family, the rostral scale is greatly enlarged and forms a prominent ridge over the dorsal surface of the snout. At the caudal end of these snakes, the tail has a variety of scale shapes, from pointed (Teretrurus sanguineus, Brachyophidium rhodogaster) to an obliquely flattened, very blunt end (most species of Rhinophis and Uropeltis). Uropeltids are designated "shieldtail" snakes because many species have a greatly enlarged terminal scale that has numerous spines or keels. The terminal scale in many is preceded by a region of thickened, keeled scales that form an oval, obliquely flattened surface. The keels and spines on these scales become encrusted with soil particles and, in wet soils, an appreciable plug of soil several millimeters thick may tightly adhere to the modified scales of the tail tip. Carl Gans has suggested that the soil plug may serve in defense against some types of burrowing predators.

Uropeltid skin colors vary from browns, grays, and black, often with light yellow or white scale edges on the ventral surface (many species), to dark, iridescent blue dorsally and a bright yellow with darker spots ventrally (Uropeltis myhendrae). A number of species are brown with dark bands rising from the

ventral surface and appear superficially similar to some species of large centipedes. Gans suggested that some Sri Lankan species may mimic small snakes of the family Elapidae, and tests with domestic chickens suggested that some ground-feeding birds, like jungle fowl, may avoid exposed uropeltids.

Among the more unusual features of uropeltids is the modification of their trunk musculature into an anterior region of red fibers rich in myoglobin and mitochondria, whereas the remainder of the trunk muscles are white. These snakes burrow by forcing their heads through the soil, anchoring the anterior trunk with tight bends of the vertebral column, then straightening the trunk anterior to these bends. Much of the work during burrowing is thus apparently done by the anterior trunk and its fatigue-resistant red muscles.

Although uropeltids retain many primitive features in skeletal and muscle arrangements, they have no pelvic vestiges, no premaxillary teeth, and reduced left lungs. Among uropeltid genera considered derived for the group (Rhinophis and Uropeltis), the maxilla is firmly anchored to the premaxilla, and many of the bones at the rear of the skull are fused. In more basal uropeltids, the maxilla is free of the premaxilla, and there is less fusion of skull elements.

Distribution

Shieldtail snakes are found in western and eastern Ghats, and the Anaimalai and Nilgiri Hills of southern and west-central India; some species reach the lowlands on the western coast of India near Bombay, and the lowlands and hills of Sri Lanka. Three of the eight genera have representatives in both India and Sri Lanka, but only one of the 47 species (Platyplectrurus madurensis) is reported from both.

Habitat

Shieldtail snakes are assumed to have originally inhabited moist soils of montane forests. Most species now occur in soils of tea plantations, kitchen gardens, and irrigated agricultural lands. It has been suggested that ranges of most species have been diminished by widespread deforestation of southern India and Sri Lanka. Although a few species are widespread and occur in lowlands, most appear to be limited to montane areas in which the temperature rarely exceeds 77°F (25°C). Many species are active at temperatures below 68°F (20°C) and appear to be intolerant of both temperature and humidity fluctuations.

Behavior

These small snakes are most often seen after rains when they emerge from their burrows. When caught, they tend to coil the anterior trunk around whatever is holding them and wave the caudal trunk around as though it were a head. When placed on the ground, they move rapidly with the head pointed downward until a soft area is found. They then burrow rapidly into the soil.

Feeding ecology and diet

All species appear to feed primarily on worms; a few species also eat caterpillars and termites. At least one species, Uropeltis rubromaculata, has been seen to emerge during rain to feed on earthworms. Although some species feed readily in captivity, there are no published details on how they feed, although different species of Uropeltis have been seen catching worms either at one end or in the middle. Worms caught in the middle were folded in half as they were dragged backward into a burrow. Feeding trials in captive specimens of seven or eight species showed that all ate earthworms and one, U. maculatus, also ate termites.

Reproductive biology

Shieldtail snakes are viviparous, producing relatively small numbers of relatively large young. The largest clutch size recorded is nine for oviductal eggs in Uropeltis, but litter sizes for most species range from two to five, depending on the size of the female. Reproductive seasons and reproductive behavior are poorly known. Young for different species have been recorded as being found anywhere from March to September, and females with embryos have been collected in most of the intervening months. In most species embryos are found in the right oviduct, but in a few species (e.g., U. phipsonii) embryos have been found in the left oviduct.

Conservation status

Many species would appear to be threatened by habitat destruction, but there are no detailed population studies.

Significance to humans

None known.

Species accounts

List of Species

Nilgiri burrowing snake
Phipson's shieldtail snake

Nilgiri burrowing snake

Plectrurus perrotetii

taxonomy

Plectrurus perrotetii Dumeril, 1851, Nilgiri Hills, Tamil Nadu State, southwestern India. No subspecies are recognized.

other common names

None known.

physical characteristics

Moderate to large uropeltids, reaching a length of 17.3 in (44 cm), either uniformly brown or purplish above and yellowish or paler brown below, or with paler spots in the center of every scale. Head slightly compressed dorsoventrally, tail compressed laterally. Tail tip formed by a laterally compressed, cup-shaped single scale with two larger spines one above the other and smaller spines on the lateral surfaces. The body is cylindrical, with ventrals about one and one-half times the width of the dorsal scales. Like species of Platyplectrurus and Teretrurus, Plectrurus perrotetii has supraocular scales separating the ocular shield from the frontal.

distribution

Nilgiri and Anamalai Hills at high elevations.

habitat

Most specimens have come from cultivated areas or gardens. Common in heavily manured soils at depths of 4–6 in (10–15 cm).

behavior

Rajendran reports that P. perrotetii will move out of their burrows into heaps of dung left on the soil by farmers, particularly when air temperatures fall.

feeding ecology and diet

This species feeds primarily on worms.

reproductive biology

Viviparous, producing three to six young born in July or August.

conservation status

Not listed by IUCN.

significance to humans

None known.


Phipson's shieldtail snake

Uropeltis phipsonii

taxonomy

Uropeltis phipsonii Mason, 1888, "Bombay Ghats." No subspecies are recognized.

other common names

None known.

physical characteristics

One of the larger species of uropeltids, reaching over 11.8 in (30 cm) in length. These snakes are dark brown above, paler below, with yellow stripes on the tail that meet ventrally at the anal scales and a variable number of yellowish triangles that extend upward from the ventral scales in the anterior trunk. The ventral and adjacent scale rows have dark brown bases (anterior half) and yellow edges. The ventrals are nearly twice the width of the adjacent scales. The head is distinctly smaller than the neck (anterior trunk). The rostral scale is large, caps the entire front of the snout, and extends caudally between the nasal scales. The eye is relatively large, occupying half or more of the ocular shield, which meets the frontal scale. There are no supraocular scales. The caudal shield is large and either flat or depressed, composed of about 40 strongly bicarinate scales and a large terminal scute.

distribution

From sea level to about 1,640 ft (500 m) in the Western Ghats of southern India.

habitat

Originally thick forest but replaced by rubber plantations. The soils these snakes live in become extremely hard during the dry season (which lasts about three months).

behavior

Uropeltis phipsonii burrows well and has been seen in captivity to move both forward and backward in its tunnels.

feeding ecology and diet

Stomach contents of wild-caught specimens contained only earthworms and humus, but captive specimens may eat earwigs as well. In captivity, this species will emerge from tunnels at night to forage on the surface. Earthworms thrown on the surface are immediately grasped and pulled back into the tunnel.

reproductive biology

Gives birth in March or April. Largest number of oviductal embryos found in a uropeltid was nine, in this species.

conservation status

Not listed by IUCN.

significance to humans

None known.


Resources

Books

Deraniyagala, P. E. P. A Colored Atlas of Some Vertebrates from Ceylon. Vol. 3, Serpentoid Reptilia. Colombo, Sri Lanka: Government Press, 1955.

Frank, N., and E. Ramus. A Complete Guide to Scientific and Common Names of Reptiles and Amphibians of the World. Pottsville, PA: NG Publishing, 1996.

McDiarmid, R. W., J. A. Campbell, and T. A. Toure. Snake Species of the World, Vol. 1. Washington, DC: The Herpetologists' League, 1999.

Pough, F. H., R. M. Andrews, J. E. Cadle, M. L. Crump, A. H. Savitzky, and K. D. Wells. Herpetology, 2nd ed. Upper Saddle River, NJ: Prentice Hall, 2001.

Rajendran, M. V. Studies in Uropeltid Snakes. Madurai, India: Madurai Kamaraj University Publications, 1985.

Smith, M. A. The Fauna of British India, Ceylon and Burma, Including the Whole of the Indo-Chinese Sub-Region. Reptilia and Amphibia. Vol. 3, Serpentes. London: Taylor and Francis, 1943.

Periodicals

Cadle, J. E., H. C. Dessauer, C. Gans, and D. F. Gartside. "Phylogenetic Relationships and Molecular Evolution in Uropeltid Snakes (Serpentes: Uropeltidae): Allozymes and Albumin Immunology." Biological Journal of the Linnean Society 40 (1990): 293–320.

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

Gans, Carl. "Aspects of the Biology of Uropeltid Snakes." Linnean Society Symposia 3 (1976): 191–204.

Gans, C., H. C. Dessauer, and D. Baic. "Axial Differences in the Musculature of Uropeltid Snakes: The Freight-Train Approach to Burrowing." Science 199 (1978): 189–192.

David Cundall, PhD

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