How close was the Jurassic Park version of the Tyrannosaurus rex to the real-life version?



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    If you’re anything like me, you “oohed” and “ahhed” during every appearance of the deadly monster, the “King of the Terrible Lizards”, the T-Rex of 1993’s Jurassic Park. But how close was the on-screen version to how it might have appeared and behaved in real life? This answer looks to contrast the beast’s two incarnations, spotlighting the two principal discrepancies: the film’s representation of Rex’s sensory perception, and the film’s representation of Rex’s top speed.

    Sensory Perception

    In one memorable movie scene, the film’s hero, Doctor Alan Grant, attempts to elude the newly-freed Rex. He stands perfectly still in front of the close-by Rex, and waits it for divert its attention elsewhere. Grant is relying upon this belief: if he stays still, Rex will not be able to see him. According to Grant (and the creators of Jurassic Park – especially author Michael Crichton), Rex can only see movement. 

    Scientific evidence contradicts this claim. In particular, a 2006 study by University of Oregon scientist Kent A. Stevens revealed that Rex “had some of the best vision in animal history”. It had a large binocular range of 55 degrees; it also possibly could have had a limiting far point (the farthest point of its vision) of 6 kilometers. In total, the Rex’s vision could have been up to thirteen times as sharp as human vision. According to Stevens, this “very sophisticated visual apparatus” meant that the Rex had almost no chance of missing Grant, if he were to be positioned in such close proximity. In fact, that very scene from Jurassic Park inspired Stevens to conduct his study. 


    Later on in the movie, Rex charges after a fleeing Jeep, maintaining a sprint speed of over 40 mph for a considerable amount of time. But would a real-life Rex have been able to reach that speed? Again, science says “no”.

    In this case, “science” comes in the form of Dr. John Hutchinson, of Stanford and more recently England’s Royal Veterinary College. Hutchinson, a biologist who specializes in evolutionary biomechanics, set up a computer model in 2002 to learn how fast Rex really could run. The model revealed that Rex would have needed to have over 80% of its muscle mass be in its legs in order to reach and maintain Jeep speed. This, of course, would have been a “physical impossibility”. Hutchinson himself said, “it would leave very little room for anything else in the body — a skeleton, other muscles, et cetera!”

    Hitchinson’s estimates placed Rex’s upper speed at somewhere between 10 and 25 mph. So, Rex was no sloth. But he certainly wasn’t quick enough to run behind a Jeep, much less maintain that speed for a period of time. Rex just did not have the leg muscle to pull that off.  


    The movie version of Rex differs from the real-life understanding of the creature in two important ways. First, Alan Grant erred in his assumption that Rex could only detect movement. Rex in fact had precise, acute vision and would have almost undoubtedly been able to spot Grant at such close range. And second, when the Rex sprinted after the Jeep, it was moving much too quickly. It was about ten to fifteen miles over its biological “speed limit”.


    Photo credit: Grafixar from

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