Although the quantity of venom expended when biting is an important aspect of the natural history of snakes, little is known regarding the quantities of venom expended during bites. Recent studies have shown that rattlesnakes appear capable of selectively allocating their venom reserves during predatory strikes, metering more venom into certain prey types and less into others. Despite much speculation, the quantities of venom expended during defensive bites are poorly understood. The purpose of this study was to examine the factors that influence venom expenditure during defensive bites by cottonmouths (Agkistrodon piscivorus), western rattlesnakes (Crotalus viridis) and western diamondbacks (C. atrox). Defensive bites were elicited by models of human limbs (warm saline-filled gloves) and by voluntary venom extractions into a parafilmcovered beaker. Biting behavior of the snakes was analyzed via slow-motion videotape review. The mass of venom expended by snakes was measured by protein assay.
The amount of venom expended during defensive bites was positively correlated with snout-vent length of the snake. Agkistrodon piscivorus and C. viridis expended similar quantities of venom in the laboratory, but C. atrox tested under less-controlled field conditions expended somewhat less venom. Different body temperatures had no discernable effect on biting or venom delivery. Venom expenditure was also proportional to the duration of fang contact during the bite. Consequently, bites of brief duration may constrain delivery of venom during a bite and therefore contribute to the occasional occurrence of “dry bites” in human snakebite victims. Quantities of venom expended in the laboratory studies were substantially greater than amounts reported previously for predatory bites of mice. Because the duration of fang contact was similar for defensive and predatory bites, it appears that snakes have the intrinsic ability to meter their venom, allocating more during defensive bites and less during predatory bites.
William K. Hayes
Ronald L. Carter
David L. Cowles
Master of Science (MS)
Year Degree Awarded
Date (Title Page)
Library of Congress/MESH Subject Headings
Snake Bites; Snake Venoms; Agkistrodon; Crotalus.
Loma Linda University Libraries
This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.
Herbert, Shelton Scott, "Factors Influencing Venom Expenditure During Defensive Bites by Cottonmouths (AGKISTRODON PISCIVORUS) and Rattlesnakes (CROTALUS VIRIDIS, CROTALUS ATROX)" (1998). Loma Linda University Electronic Theses, Dissertations & Projects. 865.
Loma Linda University Electronic Theses and Dissertations
Loma Linda University. Del E. Webb Memorial Library. University Archives