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Missouri Southern State University logo

Jillian Hackney

Biology Pre-Med Major
Physical and Biological Sciences Category


I am a Senior student in the Biology and Environmental Health Department. I have been a member of the Reptile Physiology Lab for 3 years. I have used snakes to study the relationships between constriction and striking. Most recently, I have focused on the Red-out effect in snakes. I will be graduating in May and attending medical school in the fall.  


There are numerous mechanisms that predators use during predator-prey interaction. Snakes use their limbless body in predation. The two most commonly used mechanisms during predation are constriction and striking. The mechanism of constriction, specifically, involves the wrapping or winding of the body around the prey while contracting muscles to produce high pressure. There are several hypotheses about how these high pressures impact the prey that are being constricted. Those hypotheses include suffocation, cardiac trauma and arrest, blunt force trauma, and neural damage. The Red-out effect is the most recently proposed hypothesis that aims to explain how constriction works.  It suggests that when snakes constrict their prey, they are able to drive blood and bodily fluids towards the head of their prey, quickly incapacitating them.  This eventually leads to the shutdown of the nervous system. However, to date, this has only been investigated in one snake species.  We quantified constriction pressures within both the chest and cranium of prey to find evidence for or against the newly proposed Red-out hypothesis.  We used many different snakes including pythons and boa species to measure the pressures experienced by prey in their chest and head during constriction.  

Poster Presentation