Whitebellied wormlizard

Amphisbaena alba

TAXONOMY

Amphisbaena alba Linné, 1758, "America." OTHER COMMON NAMES

French: Amphisbène blanche; German: Rote Doppelschleiche.

PHYSICAL CHARACTERISTICS

Amphisbaena alba is the largest South American amphis-baenian, with a total length of 15.7-33.4 in (400-850 mm) and a midbody diameter ranging from 1-2 in (20-25 mm). Amphisbaena alba The tail is approximately 6% of total length. It has smooth, square scales arranged in annular rings that are separated by grooves. The species is uniformly pale-

colored, although some specimens are white ventrally. The head is more or less rounded in shape. Caudal autotomy is absent in this species. Dentition is pleurodont, with conical, sharply pointed, and slightly recurved teeth. It has a large, median premaxillary tooth flanked by six smaller premaxillary teeth. Five teeth occur on the maxilla; seven teeth on the l ower jaw.

DISTRIBUTION

Throughout South America east of the Andes, Panama, and the West Indies.

HABITAT

The white-bellied wormlizard inhabits forested lowlands, soil, and leaf litter. Amphisbaena alba is rarely seen on the surface.

BEHAVIOR

Amphisbaena alba is well known to herpetologists for several unusual and interesting behavioral traits, one of which involves a unique ecological relationship with leaf-cutter ants (genus Atta). A. alba apparently follows the pheromone-marked trails of these ants to their nests, where it then takes up residence in one of the nest chambers, feeding primarily on beetle larvae and other arthropods that are also inhabitants of Atta nests.

The defensive behavior of Amphisbaena alba when threatened is also of scientific interest to behavioral biologists. When disturbed, A. alba raises its tail off the ground and waves it, while simultaneously raising its head with an open, gaping mouth. The head and tail are close together, the body held almost in a circle, which almost gives the impression of a two-headed animal. This stereotyped behavior has led to the common name "two-headed snake" applied by people who live near these animals.

FEEDING ECOLOGY AND DIET

Only a few studies examining the natural diet of Amphisbaena alba exist. These have documented that A. alba feeds primarily on small arthropods such as beetles, ants, termites, spiders, crickets, and the larvae of various insects. On the other hand, laboratory-based behavioral studies indicate that, when offered larger vertebrate prey items such as rodents, A. alba will prey on them with enthusiasm, even biting and tearing pieces out of them.

REPRODUCTIVE BIOLOGY

Amphisbaena alba is oviparous, laying eggs in clutches of eight to 16. This is the largest known clutch size for any amphis-baenian and may possibly be related to the large body size of this species. According to some studies, reproduction is seasonal and primarily restricted to the dry season.

CONSERVATION STATUS Not listed by the IUCN.

SIGNIFICANCE TO HUMANS None known. ♦

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