I’ve seen a few videos pop up on Youtube talking about the “if you don’t move, they can’t see you” bit in the original Jurassic Park. They have all attempted to “debunk” the idea, pointing to the behaviour of contemporary predators. While the real T-Rex, like most predators, could very likely see motionless prey, the “don’t move” advice comes from something different.

SPOILERS AHEAD: this piece discusses scenes from the original 1993 Jurassic Park motion picture, as well as elements from the Michael Crichton novel it is based on.

The Movie

At one point in the movie, the power in the park goes out during a storm (way to go Dennis Nedry), rendering all the electric fences inert. The animals can now move between enclosures, no longer staying in their carefully designed zones with the intended separation. The hero, palaeontologist Alan Grant is in a battery-electric Ford Explorer with the two children, Tim and Lex. A T-Rex breaks through the fence of its enclosure, and attacks the truck. Grant and Lex end up outside the vehicle, with the T-Rex bearing down on them. Grant grabs Lexi, telling her to not move. His explanation is that the T-Rex’s tracking is based on movement, and by standing still, they are basically invisible.

The movie T-Rex, of course, conforms to this. After a series of exciting maneuvers, the T-Rex moves off. Things spiral from there as we are now firmly in the movie’s second act.

The De-bunking

The de-bunking videos go to great lengths to explain that a predator that relied entirely on their prey moving wouldn’t be a very good predator. And they are right. While we don’t have the details of the T-Rex’s internal design for sight, smell, taste, and hearing, we do know some things. First, it had binocular vision. Both eyes were forward facing, and based on the size of the eye socket opening, they would have been reasonably large. The olfactory regions in the skull were quite large, allowing for significant airflow and presumably very sensitive odour detection. Hearing might have been its weakest element, with the lack of external “ears” to help focus and amplify sound. The T-Rex, though, likely had a very good sense of smell, as well as good vision with accurate depth perception.

Even if standing still would impair a T-Rex’s ability to see prey (and that happens today. It’s called camouflage), it would still be able to smell. Of course, it might not know what it’s smelling. A hominid covered in cloth and leather would be a novel experience. But smell would have also been a potential issue when it came to hiding.

The Book Explains It

The movie does make reference to something from the book: frog DNA was used to fill out the resurrected dinosaur’s DNA. The book goes deeper, though, explaining it includes specific parts around visual processing which, in some frogs, is based on movement to track prey. This made basically all the dinosaurs in the park subject to this weakness.  It wasn’t by entirely by design, though. It was a side effect that the designers didn’t think was critical. They were creating zoo animals, not attempting to repopulate the planet with dinosaurs.

This detail wasn’t described in the movie. It may have been something that occurred off-screen. The palaeontologists in the group likely understood the implications (they did in the book). This knowledge, though, wasn’t shared with the movie audience. But readers of the book would know.

It Was a Plot Device

The whole “tracking based on movement” was a plot device. This is clear based on the fact it was spelled out explicitly and carefully in the book. It was meant to give the predators a weakness that the humans could exploit. Having carnivorous dinosaurs run rampant and eat all the actors wouldn’t be all that entertaining, at least for most people. Maybe you’d be on Team Dinosaur.

Could this really happen? Maybe, on paper, hypothetically. As with any piece of fiction, a certain amount of suspension of disbelief is required. It’s a movie, not a documentary or instructional video. The point is to sit back, eat popcorn, and enjoy the story. The consequence of using frog DNA sounds plausible. Whether it actually is, or not, is irrelevant. Maybe someone watching the movie will use the whole “dino resurrection” as inspiration for something in real-life. Science fiction can do that.

I’m sure that debunking something from a piece of fiction is satisfying. It is a chance to learn something new. At least the debunkers aren’t swanning around yelling about their “superiority”.