Defensive Tail Display by Snakes and Amphisbaenians

Seventy-six species of snakes and 2 species of amphisbaenians are reported to display the tail so that it becomes unusually conspicuous. This behavior is ordinarily a response to stress, such as a sudden tactile stimulus, and is probably an antipredator strategy. The snakes can be placed in 3 groups on the basis of coloration and caudal morphology. (1) Five species are obscurely patterned or unicolored and have short tails with blunt tips. (2) Fifty-four species have contrasting or brightly colored tails without stout, blunt tips. (3) Seveeen species have either blunt, brightly colored tails or tapered, dull colored tails. Display is correlated with a brightly colored, autotomizeable tail in one amphisbaenian and with a blunt, heavily reinforced tail tip in another. A study of injuries on the tails of 52 Eryx johnii and 63 Calabaria reinhardtii suggests that these snakes display their blunt tails to misdirect the attacks of predators. Skeletal peculiarities of several boids (Charina and Eryx) and of Amphisbaena alba might be adaptations for this function of tail display. The injury data for 156 pipe snakes (Cylindrophis rufus) imply that misdirection of attack is not an important function of the display of this brightly colored species. Bright colors associated with the tail displays of many snakes and of A. fuliginosa might serve as intimidating devices, aposematic signals, or mimetic signals. The display of A. fuliginosa probably also facilitates caudal autotomy. Different functions of tail display need not, of course, be mutually exclusive. A comprehensive bibliography of tail display behavior, new information for many species, a brief discussion of terminology, speculation on the origins of tail displays, and suggestions for future investigations are also presented.