# T-Rex vision **URL:** \ **Category:** Factual Questions\ **Created:** [September 26, 2006, 12:14pm UTC](https://boards.straightdope.com/t/t-rex-vision/374197 "2006-09-26T12:14:36Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Don\_t\_Call\_Me\_Shirley](https://avatars.discourse-cdn.com/v4/letter/d/f4b2a3/32.png) [@Don\_t\_Call\_Me\_Shirley](https://boards.straightdope.com/u/Don_t_Call_Me_Shirley)\ **Post date:** [September 26, 2006, 12:14pm UTC](https://boards.straightdope.com/t/t-rex-vision/374197/1 "2006-09-26T12:14:36Z")
**"T-Rex vision is based on movement. If you stand perfectly still, he won’t be able to see you."** Of course we’ve all heard this in Jurassic Park, and this morning I heard it again while my daughter was watching Dora (and we all know Dora is very scientifically accurate!) Is this true? It sounds like an urban legend. And if it is true, how could we possibly know this from studying fossils? We don’t have any T-Rex eyes to study. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [September 26, 2006, 12:28pm UTC](https://boards.straightdope.com/t/t-rex-vision/374197/2 "2006-09-26T12:28:25Z")
If you read the book, the reason given for dinosaur vision is that they “filled in the gaps” in the DNA by taking some from frogs, and frogs are wired to respond to changes in motion rather than to simply views of objects themselves. This was too complex to try to present in a swift action movie, so they simply planted the idea early on, in the Montana segment, by having sam Neill’s character toss out a line about how the Velociraptor vision worked that way, then had him say the same thing about the T. Rex later when they’re being attacked. I’ll bet Jack Horner and the other advisors were giggling their heads off. It makes for an interesting scene, and suggests that dinosaurs are more complex and deeper than we thought (as do the poisonous saliva of the Dilophosaur and its neck frill), but there’s not a lick of evidence for it, and I doubt if any palaeontologist believes it. One thing I do like is that they show the T. Rex with a _round_ pupil (and one that reacts to light), rather than a slit pupil. Slit pupils may look cool, but I have reasons to believe it wasn’t used by a carnivore as big as T. Rex. Consider, for instance, that lions and tigers, big cats both, nevertheless have round pupils. And as for the idea of “filling in” dino DNA with amphibian DNA – HAH! BrundleRex. ---
**Author:** ![BMalion](https://avatars.discourse-cdn.com/v4/letter/b/e274bd/32.png) [@BMalion](https://boards.straightdope.com/u/BMalion)\ **Post date:** [September 26, 2006, 1:16pm UTC](https://boards.straightdope.com/t/t-rex-vision/374197/3 "2006-09-26T13:16:36Z")
Their biggest limitation was never being able to get their glasses on straight owing to those tiny, little arms. ---
**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\ **Post date:** [September 26, 2006, 1:30pm UTC](https://boards.straightdope.com/t/t-rex-vision/374197/4 "2006-09-26T13:30:12Z")
[QUOTE=BMalion] Their biggest limitation was never being able to get their glasses on straight owing to those tiny, little arms. [/QUOTE] Which of course explains the popularity of [these](http://www.eyeglasseswarehouse.com/scissor.html) during the Jurrasic. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [September 26, 2006, 1:37pm UTC](https://boards.straightdope.com/t/t-rex-vision/374197/5 "2006-09-26T13:37:59Z")
> [@](#): > > Which of course explains the popularity of these during the Jurrasic. Oh, yeah – and T. Rex and Triceratops were _Cretaceous_, not Jurassic. Horner and company must’ve been perpetually biting their hats. ---
**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\ **Post date:** [September 26, 2006, 2:34pm UTC](https://boards.straightdope.com/t/t-rex-vision/374197/6 "2006-09-26T14:34:13Z")
You know how those fashion fads persist over time. ---
**Author:** ![RickJay](https://avatars.discourse-cdn.com/v4/letter/r/bb73d2/32.png) [@RickJay](https://boards.straightdope.com/u/RickJay)\ **Post date:** [September 26, 2006, 3:10pm UTC](https://boards.straightdope.com/t/t-rex-vision/374197/7 "2006-09-26T15:10:23Z")
[QUOTE=CalMeacham] If you read the book, the reason given for dinosaur vision is that they “filled in the gaps” in the DNA by taking some from frogs, and frogs are wired to respond to changes in motion rather than to simply views of objects themselves. [/QUOTE] I believe you are confusing two separate technical issues presented in the book. The theory Dr. Grant presents about T-Rex vision is based on paleontological evidence and comparing the T-Rex to modern animals with similar cranial structures, etc. I believe it was in fact a new theory at the time Crichton wrote the book. The frog-DNA issue is presented later. > [@](#): > > This was too complex to try to present in a swift action movie, so they simply planted the idea early on, in the Montana segment, by having sam Neill’s character toss out a line about how the Velociraptor vision worked that way No; his character, Grant, specifically says Velociraptor vision DOESN’T work that way. He describes his scenario with the proposed victim (the ugly little kid) standing still because he assumes Velociraptor sees by movement, “like T-Rex,” but then gets eaten anyway because they’re more clever than that. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [September 26, 2006, 3:49pm UTC](https://boards.straightdope.com/t/t-rex-vision/374197/8 "2006-09-26T15:49:38Z")
Gotta disagree with you **RickJay**. My recollection is that, although they bring in ther frog DNA when they’re talking about the reconstruction, they _do_ use that explanation for why the T. Rex sees that way. There’s _no way_ you can glean information about the T. Rex motion vs. non-motion viewing from palaeontological evidence. It’s spinning dramatic action for the book (and movie out of some far-fetched science. As for the Montana scene, my point about his introducing the point about the T. Rex only seeing moving things _was_ introduced at that point, as I said. It’s _foreshadowing_. I might’ve gotten it wrong about velociraptos being that way, but that’s minor, and not the point I was making. ---
**Author:** ![Bryan\_Ekers](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bryan_ekers/32/183_2.png) [@Bryan\_Ekers](https://boards.straightdope.com/u/Bryan_Ekers)\ **Post date:** [September 26, 2006, 4:04pm UTC](https://boards.straightdope.com/t/t-rex-vision/374197/9 "2006-09-26T16:04:41Z")
Is the calorie content of three humans, two of them immature, worth the energy investment required to chase them for extended periods? There were apatosauruses and triceratopses on that island - why was the T-Rex wasting time and energy running after morsels? ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [September 26, 2006, 4:09pm UTC](https://boards.straightdope.com/t/t-rex-vision/374197/10 "2006-09-26T16:09:15Z")
[QUOTE=RickJay] I believe you are confusing two separate technical issues presented in the book. The theory Dr. Grant presents about T-Rex vision is based on paleontological evidence and comparing the T-Rex to modern animals with similar cranial structures, etc. I believe it was in fact a new theory at the time Crichton wrote the book. [/QUOTE] I’ve got to agree with **Cal** on that. I’ve never heard the slightest suggestion in the paleontological literature that T-rex vision would work like that of a frog, and since the closest relatives of T-rex, crocodilians and birds, are perfectly capable of seeing non-moving prey there’s no reason to think T-rex couldn’t. T-rex also had some degree of binocular vision. ---
**Author:** ![Freddy\_the\_Pig](https://avatars.discourse-cdn.com/v4/letter/f/a587f6/32.png) [@Freddy\_the\_Pig](https://boards.straightdope.com/u/Freddy_the_Pig)\ **Post date:** [September 26, 2006, 4:38pm UTC](https://boards.straightdope.com/t/t-rex-vision/374197/11 "2006-09-26T16:38:53Z")
[QUOTE=Colibri] I’ve got to agree with **Cal** on that. I’ve never heard the slightest suggestion in the paleontological literature that T-rex vision would work like that of a frog . . . [/QUOTE] **Do** frogs in fact have motion-based vision? More broadly, isn’t motion sensitivity more of a spectrum than an either/or? I know, just from formerly owning a cat, that they’re _more_ sensitive to movement than we are, presumably because they hunt small prey. If you want to get a cat’s attention, it helps to move something–it helps with a human, too, but it seems like even more so for a cat. And the instinct of a hamster, if you frighten it, is to freeze, so they must think that their predators have motion-based vision. But of course, that’s not to say that a cat _can’t_ see a stationary object. I believe there is some debate as to whether TRex hunted live prey, no? If they did, wouldn’t it be likely that their vision was _more_ motion-sensitive than otherwise? ---
**Author:** ![Astroboy14](https://avatars.discourse-cdn.com/v4/letter/a/df705f/32.png) [@Astroboy14](https://boards.straightdope.com/u/Astroboy14)\ **Post date:** [September 26, 2006, 4:56pm UTC](https://boards.straightdope.com/t/t-rex-vision/374197/12 "2006-09-26T16:56:40Z")
[QUOTE=Bryan Ekers] Is the calorie content of three humans, two of them immature, worth the energy investment required to chase them for extended periods? There were apatosauruses and triceratopses on that island - why was the T-Rex wasting time and energy running after morsels? [/QUOTE] One of those morsels was [Laura Dern](http://en.wikipedia.org/wiki/Laura_Dern). I understand, Mr. T-Rex… I understand. ---
**Author:** ![Don\_t\_Call\_Me\_Shirley](https://avatars.discourse-cdn.com/v4/letter/d/f4b2a3/32.png) [@Don\_t\_Call\_Me\_Shirley](https://boards.straightdope.com/u/Don_t_Call_Me_Shirley)\ **Post date:** [September 26, 2006, 5:02pm UTC](https://boards.straightdope.com/t/t-rex-vision/374197/13 "2006-09-26T17:02:48Z")
[QUOTE=CalMeacham] Gotta disagree with you **RickJay**. My recollection is that, although they bring in ther frog DNA when they’re talking about the reconstruction, they _do_ use that explanation for why the T. Rex sees that way. There’s _no way_ you can glean information about the T. Rex motion vs. non-motion viewing from palaeontological evidence. It’s spinning dramatic action for the book (and movie out of some far-fetched science. As for the Montana scene, my point about his introducing the point about the T. Rex only seeing moving things _was_ introduced at that point, as I said. It’s _foreshadowing_. I might’ve gotten it wrong about velociraptos being that way, but that’s minor, and not the point I was making. [/QUOTE] Hey Cal- You recollection, in addition to being incorrect according to my recollection, does not even make logical sense. If the T-Rex as bred for Jurrasic Park has limited vision due to the frog DNA, then how would the doctor know about it at the beginning of the movie, before he has heard of Jurassic Park or even contemplated cloning dinosaurs? ---
**Author:** ![Don\_t\_Call\_Me\_Shirley](https://avatars.discourse-cdn.com/v4/letter/d/f4b2a3/32.png) [@Don\_t\_Call\_Me\_Shirley](https://boards.straightdope.com/u/Don_t_Call_Me_Shirley)\ **Post date:** [September 26, 2006, 5:09pm UTC](https://boards.straightdope.com/t/t-rex-vision/374197/14 "2006-09-26T17:09:36Z")
:smack: **Your** recollection. Carry on… ---
**Author:** ![Darwins\_Finch](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darwins_finch/32/20304_2.png) [@Darwins\_Finch](https://boards.straightdope.com/u/Darwins_Finch)\ **Post date:** [September 26, 2006, 5:10pm UTC](https://boards.straightdope.com/t/t-rex-vision/374197/15 "2006-09-26T17:10:30Z")
In the book, during the _T. rex_ attack on the road, Grant realizes that the _T. rex_ couldn’t see him: > [@Jurassic Park](#): > > No, the tyrannosaur couldn’t see him. Not if he stood motionless. And in a detached academic corner of his mind he found an explanation for that, a reason why – Unfortunately, after a quick skim, I couldn’t find the explanation for that… I do recall the frog DNA being implicated (it was also explicitly mentioned as the cause for the supposedly-all-female dinosaurs beginning to breed), but I can’t find the exact passage in the book. I also seem to recall the idea was retracted in the sequal, _The Lost World_. In the movie version, the whole “vision based on movement” thing was just presented as fact, without explanation. It is, perhaps, also worth noting that in the book, it is explained that they did occassionally use avian DNA to fill in the gaps: > [@](#): > > “When you made your dinosaur DNA,” Grant said, “you were working with fragmentary pieces, is that right?” > “Yes,” Wu said. > “In order to make a complete strand, were you ever required to include DNA fragments from other species?” > “Occassionally, yes,” Wu said. “It’s the only way to accomplish the job. Sometimes we included avian DNA, from a variety of brids, and sometimes reptilian DNA.” > “Any amphibian DNA? Specifically, frog DNA?” After Wu checks his records, he finds that they did, in fact, use frog DNA. So it’s not the case that they _only_ used frog DNA to fill in DNA gaps, at least in the book. In the movie, I think they just went for all-frog DNA for filling in the missing pieces. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [September 26, 2006, 5:14pm UTC](https://boards.straightdope.com/t/t-rex-vision/374197/16 "2006-09-26T17:14:33Z")
> [@](#): > > Hey Cal- > You recollection, in addition to being incorrect according to my recollection, does not even make logical sense. If the T-Rex as bred for Jurrasic Park has limited vision due to the frog DNA, then how would the doctor know about it at the beginning of the movie, before he has heard of Jurassic Park or even contemplated cloning dinosaurs? In the book, he didn’t, and it wasn’t a tenet of Palaeontological belief, either. It emerged that the T. Rexes in Jurassic Park had this frog-based limitation on its vision because of the frog DNA, but he didn’t know that until they observed the bahavior in the T. Rex. For the m,ovie, they simplified it by making the weird motion-based T. Rex vision thing a well-known fact so they could introduce it early. I guess they thought it would be too much information for the audience if they threw it all at them at once. It may be illogiocal, but it ain’t my doing – blame Crichton and the script. Actually, there’s even more in the script that smacks of hasty revision. They make a big deal out of using frog DNA to fill in gaps in the dino DNA (just as in the book), but then they fail to use this detail to explain the two unexpected dinosaur behaviors that result. One is the motion-based vision. The other is the way some dinosaurs change sex spontaneously – just as some lower life forms do under stress – this allowing the dinosaursd (who were all cloned as females) to obtain males and mate. In the book this is made clear. In the movie they simply pass it off asc “Life Will Find a Way”. I don’t recommend you try that explanation when all of humanity consists of ten guys on a desert island. To sum up: Book: Dinosaurs reconstructed with frog DNA, which gives them frog motion-sensitivity (and insensitive to unmoving things), and allows some of them to change sex. Nobody’s aware of these features until they encounter them among the living dinosaurs. Movie: T. rex is known to be insensitive to stationary items, but tracks movement. It’s simply asserted that this is known. Later on, it’s discovered that some dinosaurs are reproducing, but it’s not explained how. They do make a deal about the dinosaurs having gaps filled in with frog DNA, but no conclusions or results are drawn from this (just like the lysine deficiency, which gets mentioned in the film, but has even fewer consequences tha in the book). The practical result of filling in Dinosaur DNA wwith frog DNA seems to me likely to produce unworkable creatures, at best. The only plausible reason for Crichton introducuing the idea is to get a toehold of plausibility for both the motion vision and the sex change. Otherwise, you’d think they’d use reptile or bird DNA, as something a lot close than frog. But it’s a real reach. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [September 26, 2006, 5:18pm UTC](https://boards.straightdope.com/t/t-rex-vision/374197/17 "2006-09-26T17:18:57Z")
Regarding the movie, as has been noted, Dr. Grant does bring up the issue of T-rex vision in the Montana scene, but does not give a reason for it: From [IMDB](http://www.imdb.com/title/tt0107290/quotes) > [@](#): > > Dr. Alan Grant: Try to imagine yourself in the Cretaceous Period. You get your first look at this “six foot turkey” as you enter a clearing. He moves like a bird, lightly, bobbing his head. And you keep still because you think that maybe his visual acuity is based on movement like T-Rex, he’ll lose you if you don’t move. But no, not Velociraptor. You stare at him, and he just stares right back. And that’s when the attack comes. Not from the front, but from the side, from the other two 'raptors you didn’t even know were there. Because Velociraptor’s a pack hunter, you see, he uses coordinated attack patterns and he is out in force today. And he slashes at you with this… a six-inch retractable claw, like a razor, on the the middle toe. He doesn’t bother to bite your jugular like a lion, say… no no. He slashes at you here… or here… or maybe across the belly, spilling your intestines. The point is… you are alive when they start to eat you. So you know… try to show a little respect. ---
**Author:** ![Darwins\_Finch](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darwins_finch/32/20304_2.png) [@Darwins\_Finch](https://boards.straightdope.com/u/Darwins_Finch)\ **Post date:** [September 26, 2006, 5:58pm UTC](https://boards.straightdope.com/t/t-rex-vision/374197/18 "2006-09-26T17:58:30Z")
For what it’s worth, I was correct about the diea being retracted in _The Lost World_: > [@The Lost World (Michael Crichton version)](#): > > Sara Harding said, “Why did Dodgson just stand around like that? That’s not the way to act around predators. You get caught around lion, you make a lot of noise, wave your hands, throw things at them. Try to scare them off. You don’t just stand there.” > > "He probably read the wrong research paper, "Malcom said, shaking his head. “There’s been a theory going around that tyrannosaurs can only see movement. A guy named Roxton made casts of rex braincases, and concluded that tyrannosaurs had the brain of a frog.” > […] > “Roxton,” Levin said, “believed that tyrannosaurs had a visual system like an amphibian: like a frog. A frog sees motion but doesn’t see stillness. But it is quite impossible that a predator such as a tyrannosaur would have a visual system that worked that way. Quite impossible. Because the most common defense of prey animals is to freeze. A deer or something like that, it senses danger, and it freezes. A predator has to be able to see them anyway. And of course a tyrannosaur could.” > > Over the radio, Levine snorted with disgust. “It’s just like the other idiotic theory put forth by Grant a few years back that a tyrannosaur could be confused by a driving rainstorm, because it was not adapted to wet climates. That’s equally absurd.[…]I’m quite sure tyrannosaurs saw plenty of rain, and the evolved to deal with it.” > > “So is there any reason why a tyrannosaur might not attack somebody?” Malcom said. > > “Yes, of course. The most obvious one,” Levine said. > > “Which is?” > > “If it wasn’t hungry. If it had just eaten another animal. Anything larger than a goat qwould take care of its hunger for hours to come. No, no. The tyrannosaur sees fine, moving or still.” That passage also implicates Grant as theorizing that the tyrannosaur could not see him, not because of frog DNA, but because of the rainstorm during that initial attack in _Jurassic Park_. I’m not sure if this is a case of revisionism on the part of Crichton, or if that’s what he really had in mind regarding Grant’s explanation in that academic corner of his mind, and somehow readers made the non-implicit connection with the frog DNA thing. ---
**Author:** ![Don\_t\_Call\_Me\_Shirley](https://avatars.discourse-cdn.com/v4/letter/d/f4b2a3/32.png) [@Don\_t\_Call\_Me\_Shirley](https://boards.straightdope.com/u/Don_t_Call_Me_Shirley)\ **Post date:** [September 26, 2006, 5:59pm UTC](https://boards.straightdope.com/t/t-rex-vision/374197/19 "2006-09-26T17:59:51Z")
> [@Cal Meacham](#): > > They do make a deal about the dinosaurs having gaps filled in with frog DNA, but no conclusions or results are drawn from this In the movie, the frog DNA is used to conclusively explain the gender change. If not for this, there would have been no reason for the movie to even bring it up. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [September 26, 2006, 6:02pm UTC](https://boards.straightdope.com/t/t-rex-vision/374197/20 "2006-09-26T18:02:02Z")
[QUOTE=Freddy the Pig] **Do** frogs in fact have motion-based vision? More broadly, isn’t motion sensitivity more of a spectrum than an either/or? I know, just from formerly owning a cat, that they’re _more_ sensitive to movement than we are, presumably because they hunt small prey. If you want to get a cat’s attention, it helps to move something–it helps with a human, too, but it seems like even more so for a cat. And the instinct of a hamster, if you frighten it, is to freeze, so they must think that their predators have motion-based vision. But of course, that’s not to say that a cat _can’t_ see a stationary object. [/quote] The wiring of a frog’s retina enables it to detect small moving objects at that level; it has “bug detectors.” In higher vertebrates that integration is done at the level of the brain, rather than in the retina. Frogs can detect both small and large moving objects (prey and predators) and large stationary objects (rocks, water); they are not so good at detecting small stationary objects. Most reptiles and higher vertebrates have no problem with the latter. > [@](#): > > I believe there is some debate as to whether TRex hunted live prey, no? If they did, wouldn’t it be likely that their vision was _more_ motion-sensitive than otherwise? Some allege T-rex was a scavenger (unlikely IMO for ecological reasons). If so it _might_ be less sensitive to movement (although there is no actual reason to suppose it was, since this is not true of other scavengers), but of course then it wouldn’t be chasing people around. [Next page](https://boards.straightdope.com/t/t-rex-vision/374197.md?page=2)