Kinematics of Egg-Eating by the Specialized Taiwan Snake Oligodon formosanus (Colubridae)

• Published in: Journal of herpetology 1993-09, Vol.27 (3), p.320-327
• Main Authors: Coleman, Karen, Rothfuss, Leslie A., Ota, Hidetoshi, Kardong, Kenneth V.
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Capsules; Eggs; Eggshells; Feeding. Feeding behavior; Fundamental and applied biological sciences. Psychology; Jaw; Maxilla; Reptiles; Snakes; Swallowing; Teeth; Turtles; Vertebrates: anatomy and physiology, studies on body, several organs or systems
• ISSN: 0022-1511; 1937-2418
• DOI: 10.2307/1565154

The Taiwan colubrid snake Oligodon formosanus feeds almost exclusively upon the eggs of other reptiles. Snakes that specialize on the eggs of birds usually swallow eggs whole then crush them. Oligodon instead uses enlarged, blade-like rear maxillary teeth to make repeated slashes in the leathery egg shell, inserts its head, and swallows the yolk. The mechanics of cutting involve cycles of extreme displacement of the maxillary bone, whose blade-like teeth are swung in arcs to make ever deeper slashes in the shell until a slit is formed. The cycles during cutting involve protraction, engagement, and retraction of the palatomaxillary arch of one side while the contralateral jaws maintain a continuous hold on the egg surface. The slit is enlarged by repeated cutting motions until the snake can push its head through this opening and into the interior of the egg, where it swallows the yolk and young embryo. The basic feeding behavior of colubrids has been modified in O. formosanus in two ways. First, the reciprocating, unilateral pattern has become repeating and unilateral. Second, palatomaxillary arch displacements characteristically arising during deglutition in other colubrids arise earlier in feeding by O. formosanus during egg opening. The egg-eating specializations of O. formosanus give it access to an energy rich food (yolk) and to a wider range of foods (small to large eggs) than are available to generalized snakes of similar size.