Predator dinosaurs may have been night-hunters
April 14th, 2011
02:20 PM ET

Predator dinosaurs may have been night-hunters

Following on the heels of the discovery of a new dinosaur species, another interesting piece of research has come out about these prehistoric monsters: Many carnivorous species were nocturnal.

The study, published in the journal Science, casts doubt upon the idea that hundreds millions of years ago (up until about 65 million years ago), most dinosaurs were active only during the day, leading mammals to hide from them in the shade. In fact, several carnivorous dinosaur species were probably sleeping during the day, and would hunt at night, new research suggests.

"It gives us a new view of how to reconstruct the dinosaur era and how the environment in the Mesozoic, the dinosaur era, was actually used," said Lars Schmitz, a postdoctoral researcher in the Department of Evolution and Ecology at the University of California, Davis, and co-author of the study. "That's a totally new component of paleontology."

One such species that the researchers studied is the velociraptor, a feathered predator that lived about 71 million to 75 million years ago.

Nocturnal species would be expected to have eyes that function well in really dim light, Schmitz says. There's a key eye structure that we mammals lack, but that dinosaurs, lizards and birds all share:  the scleral ring. Researchers wanted to find out how big this bony ring was, and generally the size of the eye socket, in living species and their ancestors. They examined 33 fossils of extinct creatures (dinosaurs, ancestral birds and pterosaurs) and 164 species that are alive today.

In the living species, the researchers found a clear pattern: Animals that are active during the day have a small opening in the center of the scleral ring, while the nocturnal ones have a much larger opening to collect as much light as possible. Those that are active during both time periods have a ring opening that's between the average size of those two.

For example, most geckos have large scleral ring openings and are active at night; monitor lizards, on the other hand, are active in the daytime and have much smaller scleral ring openings. Small carnivores in the study that were found to be nocturnal have scleral rings with a wide opening, Schmitz said.

The researchers then applied their insights about living species to the extinct ancestors of today's animals. Their findings suggest that predators were likely to be active during the night, and that large plant eaters were likely to be active both day and night. The mix of day-active, night-active, and day-and-night-active was comparable to what we see today, he said.

"It actually fits well with how the velociraptor was reconstructed in 'Jurassic Park,' " Schmitz said. "The night attack - actually, we can confirm that now by looking at its eye structure."

At some point down the line, this research may have something to say about extinction itself: Do nocturnal and diurnal species have different extinction patterns? This is an open question, Schmitz says.

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Filed under: Animals • Dinosaurs
soundoff (86 Responses)
  1. Cesar

    And all this time I thought T-Rex hunted in the day time. This new theory makes sense; that's what lions do.

    April 14, 2011 at 3:39 pm | Report abuse |
    • Nancy

      No real surprise. But the fossil image they show is of a pterosaur, neither a dinosaur nor a noctural creature - they flew.

      April 14, 2011 at 8:36 pm | Report abuse |
    • Dino_man

      T-Rex was actually a scavenger and an opportunist hunter. He also had very poor eyesight and overly an overly developed occipital lobe. I also find it funny that the picture that accompanies this article is a pterosaur and is not a dinosaur at all.

      April 14, 2011 at 9:02 pm | Report abuse |
    • michael

      Bats fly.

      April 14, 2011 at 10:33 pm | Report abuse |
    • michael

      The bottom line is you have no idea what any of them did because you weren't there........hence, the reason why so many theories keep coming along......they hunted during the, at night.....keep guessing and one day, you will still not know if you are right or not.....never will....

      April 14, 2011 at 10:38 pm | Report abuse |
    • Andrew

      michael, just like I don't need to see a person get shot to know that a person coming into a hospital yelling "I've been shot" with a bullet wound in his gut was probably shot, scientists don't need to have been there to provide evidence supporting various theories about dinosaur behaviour.
      If you doubt the validity of the findings, explain what's wrong with the actual paper.

      Linked here cause CNN doesn't link to peer reviewed literature... because CNN doesn't know how to do science reporting.

      April 14, 2011 at 11:28 pm | Report abuse |
    • elandau

      The link to the original research paper is now in my article above. Thanks for reading!

      Elizabeth Landau, CNN

      April 14, 2011 at 11:40 pm | Report abuse |
    • Mmmmm

      Man, she gets a CNN logo..?

      April 14, 2011 at 11:47 pm | Report abuse |
    • Andrew

      Wow, screaming for the original paper to be linked actually worked! I'm amazed, awesome!

      Thanks! Sorry I was rude it's just I have noticed that often when CNN does science reporting that tends to be omitted, and as a science student myself, it's one of those things I feel shouldn't be neglected. I sincerely doubt, after all, that I'm the only reader who likes seeing the original source. 🙂

      April 14, 2011 at 11:52 pm | Report abuse |
    • Logan

      I love a good debate...

      April 15, 2011 at 12:38 am | Report abuse |
    • amphiox

      T-rex was likely both a scavenger and a hunter, but it is not yet clear which it did more of, or which it preferred. T-rex's vision was most likely not poor at all – it had relatively large optic lobes in its brain, based on endocasts. It's just that's its olfactory bulbs were even more impressive, relatively speaking, which suggests that it a good vision, and stupendous sense of smell.

      April 15, 2011 at 1:27 am | Report abuse |
  2. banasy

    Most predators *today* prey at night....and predators of the animal kingdom also; makes sense that predator dinosaurs did too. Fascinating.

    April 14, 2011 at 3:45 pm | Report abuse |
    • Nerd

      No, it's not facinating. It's boring.

      April 14, 2011 at 5:24 pm | Report abuse |
    • Norm

      That's a very general and broad assumption there. The main thing here is, Dinosaurs were reptiles. Though it was warmer millions of years ago, these animals still need the sun for energy.

      April 14, 2011 at 8:16 pm | Report abuse |
    • Nancy

      Norm. Dinosaurs are indeed reptiles, but it is pretty clear that they were not uniformly ectotherms (deriving energy from the sun). Some were too big to have a body warm up in the sun; they maintained a constant metabolic body temperature like mammals and birds (which, believe it or not, are ALSO dinosaurs).

      April 14, 2011 at 8:46 pm | Report abuse |
    • Dino_man

      Nancy, the term you are looking for is exotherms and mammals are definitely not dinosaurs. We have a different skull type and a neocortex

      April 14, 2011 at 9:15 pm | Report abuse |
    • Dino_man

      Oh, and nancy....the ones that are "too big" were called gigantotherms and DID NOT maintain a constant body temp. They had a heck of a time shedding heat....

      April 14, 2011 at 9:17 pm | Report abuse |
    • amphiox

      Dinosaurs were archosaurs. Archosaurs today include crocodilians and birds. In other words, the family includes both warm blooded and cold blooded creatures. The small and medium theropods were probably warm blooded, or at least partly so.

      April 15, 2011 at 1:29 am | Report abuse |
  3. Jazzzzzzzz

    Wish I had a libarary at my fingertips for info as well like Banasy 🙂

    April 14, 2011 at 3:54 pm | Report abuse |
  4. Jazzzzzzzz

    Bahhhh bahhhh hello. I'm a sheep-asaurs

    April 14, 2011 at 4:43 pm | Report abuse |
  5. banasy


    It's not like I've read *every* book!

    If you want to know who probably has, it's Philip. Hands down! 🙂

    April 14, 2011 at 4:43 pm | Report abuse |
  6. Doogle

    Where there's a niche, there is a way...

    April 14, 2011 at 5:03 pm | Report abuse |
    • michael

      And, a nerd......

      April 14, 2011 at 10:35 pm | Report abuse |
  7. jazzzzzzzzz

    Blah blah blah. What's next: we find out dino learned to wipe their botties with leaves after they're done number duo?

    April 14, 2011 at 5:23 pm | Report abuse |
    • Arran Webb


      April 14, 2011 at 6:05 pm | Report abuse |
  8. Nerd

    Yes, it's fascinating. I'm boring.

    April 14, 2011 at 5:26 pm | Report abuse |
  9. just to p iss you off

    Evolution is real. Dinosaurs evolved into the new breeds of Exxon, BP, Shell and Citgo. Now with the price of the Dino's oily decedents, nature once again proves the world can't support them... at $4 a gallon.

    April 14, 2011 at 5:33 pm | Report abuse |
    • Amanda

      Are you aware that oil does not derive from Dinosaurs? Oil comes from tiny sea creatures, mostly planktonic, who make oils to help them mobilize through the water... do some research.

      April 14, 2011 at 9:29 pm | Report abuse |
    • Amanda

      I'm a student of geology, that's how I know that little bit of info. Although I don't agree with extraction of oil and other hydrocarbons at all.

      April 14, 2011 at 9:33 pm | Report abuse |
    • amphiox

      However, several of the major oil-producing geologic eras occurred during the Mesozoic. (For example, late Cretaceous). So, while dinosaurs did not directly become oil, a lot of today's oil formed from organisms that lived with or near dinosaurs.

      April 15, 2011 at 1:32 am | Report abuse |
  10. ElephentNutts

    I wish i had banasy at my finger tips..! I'd love to hose her down 4 a 4-min. Body treatment ....... For FREE ! Of course !! Wheres little ruffnutt these days ! Send me a tweet Jazz7 /twitter ... Gotta go boy i got a gusher coming on

    April 14, 2011 at 6:08 pm | Report abuse |
  11. Arran Webb

    It's a nice story. Large flying lizards and egg laying bats and crocodiles with feathers. It is a wonderful story. I like the dragon stories better. Fire breathing! We pay a lot of money to have dirt diggers find these impressions in the ground. The Greeks found the pictures in the sly.

    April 14, 2011 at 6:09 pm | Report abuse |
    • Nancy

      Do i detect a note of skepticism?

      April 14, 2011 at 8:49 pm | Report abuse |
    • Noah

      You're an idiot...

      April 14, 2011 at 8:50 pm | Report abuse |
    • FactsOnlyPlease

      A "story" that is supported by the facts. I feel sorry for you

      April 15, 2011 at 1:17 am | Report abuse |
    • amphiox

      Large flying lizards? No, pterosaurs were archosaurs, while lizards a lepidosaurs. Pterosaurs are more closely related to birds than they are to lizards.

      Egg laying bats? No. All bats are placental mammals.

      Crocodiles with feathers? Not as far as we yet know. Feathers appear to have evolved in dinosaurs (probably the theropods) after their lineage split from their common ancestor with the crocodylians.

      If you want to make fun of something, you ought to at least know something about it. Otherwise you just come across as a fool.

      April 15, 2011 at 1:38 am | Report abuse |
  12. raven

    Pretty cool how such information can still be gleaned. First the feathers, now night vision. So many things yet to learn about our world ,past and present.

    April 14, 2011 at 6:14 pm | Report abuse |
  13. Andyvon

    I agree with Nerd, although I wouldn't use the word 'boring'.

    I'm just surprised that this has just been announced as a finding. Many modern animals, both herbivorous and predatory, are active at night as the hours of darkness confer many benefits on those able to take advantage. The advantages of darkness were the same for the dinosaurs so why should anyone have considered them to be any different to today's animals?

    April 14, 2011 at 6:23 pm | Report abuse |
    • par for the course

      it was published in Science, not "announced as a finding". And publication in Science means nothing more than it's been peer reviewed for not being total crackpot and being a technically sound study. That is a LONG way from there being any kind of agreement among scientists about the validity of the conclusion. In fact, it's the FIRST step to presenting the idea for debate, not the last. This is how other paleontologists will find out about the work. The media tends to shortcut the whole process and announce hypothesis and theory as fact.

      April 14, 2011 at 7:37 pm | Report abuse |
  14. Tony Gerards (The Other Side Of Things)

    Hey – banasy and jazz7 ,philip does'nt know SH – IT ..! He justs downloads and prints out the knowledge , then copys whats written and posts it as if he knows what he is talking about like an internet-junkie ... Get with program half the nonesense he posts he knows nothing about !!!

    April 14, 2011 at 6:27 pm | Report abuse |
  15. banasy

    Hi, Tony Gerards (The Other Side Of Things). Interesting statement. You know this because...?

    April 14, 2011 at 8:12 pm | Report abuse |
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