In this dissertation, I examined some of the factors that influence venom expenditure by viperid and elapid snakes in both predatory and defensive contexts. I also considered the consequences of venom delivery into human snakebite victims. In the first of four experiments, In the first experiment, I explored whether the Black-necked Spitting Cobra (Naja nigricollis) metered venom by differential venom gland contraction. Differences in duration of venom flow and venom expended confirmed that this species ejects markedly greater quantities of venom during biting than spitting by varying the duration of venom gland contraction. In the second experiment, I studied the effects of varying levels of perceived threat on how snakes bite defensively and allocate their venom. Two viperid snakes (Calloselasma rhodostoma, Bothrops atrox) and one elapid (Naja annulifera) demonstrated risk assessment by biting more quickly and expending more venom when biting model human limbs at higher levels of threat. In the third experiment, I examined whether rattlesnakes expend optimal quantities of venom when feeding on rodent prey. The results supported my prediction that the quantity of venom rattlesnakes typically inject into mice produces the most rapid incapacitation and death for the least amount of venom. Moreover, the optimum dose for securing larger rodent prey should be greater than that for smaller prey, In the fourth experiment, I explored the potential of denim cloth (i.e., blue jeans) to interfere with and reduce the amount of venom injected during a defensive bite to a human. When Southern Pacific rattlesnakes (Crotalus ore ganus hellen) were provoked to bite bare and denim-covered human limb models, the presence of denim reduced the amount of venom injected by approximately two-thirds for both small and large rattlesnakes. Thus, clothing can be considered a simple, low-cost, and potentially effective means of providing a measure of protection from snakebite when in the habitat of venomous snakes. Collectively, these studies add to a growing body of literature documenting the mechanisms, adaptive value, and human importance of venom expenditure by snakes.
School of Science and Technology
William K. Hayes
Sean P. Bush
Leonard R. Brand
Stephen G. Dunbar
Ernest R. Schawb
Doctor of Philosophy (PhD)
Year Degree Awarded
Date (Title Page)
Library of Congress/MESH Subject Headings
Poisonous snakes -- Behavior; Poisonous snakes -- Venom; Rattle snakes; Venom.
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, "Venom Expenditure by Viperid and Elapid Snakes: Mechanisms, Adaptation, and Application" (2007). Loma Linda University Electronic Theses, Dissertations & Projects. 576.
Loma Linda University Electronic Theses and Dissertations
Loma Linda University. Del E. Webb Memorial Library. University Archives