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. ?

    This explains the OprahEatABagOfCheeseburgersasaures.

    April 14, 2011 at 8:45 pm | Report abuse |
  2. Nancy

    They do exist today - they are called birds. Brds ARE a type of dinosaur.

    April 14, 2011 at 8:48 pm | Report abuse |
    • Mmmmm

      So are alligators lizards and crocodilles...

      April 14, 2011 at 11:49 pm | Report abuse |
    • Mmmmm

      I hate it when your reply fails to link to the intened comment...what is up with that CNN?

      April 14, 2011 at 11:51 pm | Report abuse |
  3. Decro435

    Maybe they could finish off America together no matter what race. Everyone is sick of you.

    April 14, 2011 at 8:48 pm | Report abuse |


      April 14, 2011 at 11:30 pm | Report abuse |
  4. Anon

    not surprising
    some dinosaurs have to have hunted at night

    April 14, 2011 at 9:01 pm | Report abuse |
    • Anon

      must have*

      April 14, 2011 at 9:02 pm | Report abuse |
  5. Dino_man

    @Norm Dinosaurs were not reptiles. They share a common lineage with reptiles.

    April 14, 2011 at 9:04 pm | Report abuse |
    • Nancy

      Dinosaurs were reptiles. Birds, their descendants, are reptiles. Look up "nonavian dinosaur". The term refers to dinosaurs that were not birds. .

      April 14, 2011 at 10:01 pm | Report abuse |
    • amphiox

      The term "reptile" is a non-scientific term that does not actually have a completely precise definition. Archosaurs (Dinosaurs, crocodylians, pterosaurs, birds) and lepidosaurs (lizards, snakes, mosasaurs) are diapsids. Mammals and mammal-like reptiles are synapsids. Turtles are either anapsids or derived diapsids (still up in the air). All of these groups together are amniotes. The amniotes plus the amphibians are tetrapods.

      April 15, 2011 at 1:41 am | Report abuse |
  6. Dino_man

    @Andyvon the running theory (up until know i suppose, but I think most paleontologists would agree) was that dinosaurs were primarily active during the day as they were cold-blooded. The dinos that could have been active at night were gigantotherms like the apatosaur and other large creatures. What gave mammals an edge over dinosaurs was their enhanced eyesight (they were primarily nocturnal) and thus thrived after the late cretaceous mass extinction that occurred 65 million years ago

    April 14, 2011 at 9:08 pm | Report abuse |
    • Nancy

      "cold-blooded" is not an acceptable term. Poikilothermic.

      April 14, 2011 at 10:25 pm | Report abuse |
    • amphiox

      Poikilothermic is the proper scientific term. "Cold-blooded" is like "reptile", a colloquial term. Not as precise, but still acceptable to use, particularly if you're not talking to scientists.

      April 15, 2011 at 1:43 am | Report abuse |
  7. chirsto

    noooooooo really!!!!!! It took scientist to figure this out....
    oh but wait! what do I see. Is that a flying dinosaur. but but but but- I'm confused! I thought you guys told me all dinosaurs evolved to birds. why do i see a bird fossil ( a flying teratactil) on a rock. did it ever occur to u guys that maybe that specie of birds evolved to the birds we have today. noooo!!!!!!!!!!!! "all land dinosaurs evolved to birds". evolutionary impossible!

    "read this in my daughters 4th grade boo. "All dinosaurs evolved to birds" and in the back they have a teratactil. I know what some of u r going to say." teratactil r not birds" – maybe they evolved to birds.

    April 14, 2011 at 9:11 pm | Report abuse |
    • Dino_man

      I can only pray that you did not reproduce and that you were kidding when you siad you have a daughter. Not all dinos evolved into birds....things like the maniraptor and others that evolved feathers possibly did. The pterosaur is not a dinosaur. It evolved from thecodonts along with crocodiles and dinosaurs. They share a common lineage.

      April 14, 2011 at 9:21 pm | Report abuse |
    • Andrew

      1) 4th grade science books are rarely good sources of scientific information, they're generally better for highly distilled and oversimplified generalisations based on science, but lack any of the nuance regarding the issues.

      2) Not all dinosaurs evolved into birds, birds specifically come from theropods, meaning any dinosaurs to branch off from theropods, including all Ornithischia, did not become birds. They all died out. Again, 4th grade science books are not a very good source of information.

      3) Pterodactyl were not dinosaurs in the first place, they were winged reptiles, but they belonged to a very different group of organisms. Dinosauria (dinosaurs) is an order that came about long after the pterosaurs branched off.

      April 14, 2011 at 11:24 pm | Report abuse |
  8. Dino_man

    @Nancy mammals are not dinosaurs. Mammals have a synapsid skull and developed out of mammal-like reptiles like the cynodont. Birds are like you said dinosaurs (they have diapsid skulls)

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

      Dinos and mammals appeared at the same time in the fossil record 225 million years ago

      April 14, 2011 at 9:31 pm | Report abuse |
    • Nancy

      Read what I wrote. I never stated (and I don't believe) that dinosaurs are mammals.You must have me confused with someone else.

      April 14, 2011 at 10:03 pm | Report abuse |
  9. parag

    why do we care now if they had night vision? just feel some of the researches are just not worth doing...

    April 14, 2011 at 9:36 pm | Report abuse |
    • Dino_man

      It is nice to know our roots and whom we shared the planet with. And by "we" I mean eomaia scansoria...

      April 14, 2011 at 9:46 pm | Report abuse |
    • Nancy

      Dino-man. Poor answer. Dinosaurs are not our roots. They are not our ancestors. And we no longer share the planet with the creatures being studied. It is knowledg for knowledg sake. parag will never understand this idea.

      April 14, 2011 at 10:06 pm | Report abuse |
    • Dino_man

      I didn't day that dinosaurs are our roots. I said that our ancestors shared the planet with them. I guess you don't know who eomaia scansoria is....It was the first primate. Eomaia scansoria didn't live with the dinos but other mammals did that eventually lead to us. and lighten up jeez

      April 14, 2011 at 11:25 pm | Report abuse |
    • amphiox

      Eomaia I think was the first (or earliest currently known) placental mammal (hence the name, eomaia = "dawn mother"), rather than the first primate. The earliest known primate I think was Purgatorius (but perhaps that fossil is disputed?), though it too, did live contemporaneously with the very last of the dinosaurs.

      April 15, 2011 at 1:46 am | Report abuse |
    • amphiox

      Studying dinosaurs gives us a greater perspective on life in general and its history. This was a group of large, dominant land animals arising from a very different branch of the tree of life than modern mammals, filling many of the same niches, but using different sets of adaptions and body types. It is generally considered that understanding life is, over all, a good thing, since we ourselves are alive and depend on other lifeforms.

      April 15, 2011 at 1:49 am | Report abuse |
  10. dinuuuuusuuuur

    Some dinosaurs hunted in moring, some are in afternoon, some are in evening, and rest are in the night. Very effecient....good job for this research.

    April 14, 2011 at 10:46 pm | Report abuse |
  11. ed Bailey

    Whew, I can tell I missed a class. A finch isn't a cousin of a brontasauras? O boy. Of course divrsity around the clock must have been common or else the expressway would have been crowded!

    April 14, 2011 at 11:01 pm | Report abuse |
  12. D



    April 14, 2011 at 11:03 pm | Report abuse |
  13. Andrew


    I mean, I'm glad you mentioned it's on Science, cause I was able to find it myself, but proper science reporting shouldn't force the reader to have to search for the article, you should link it yourself.

    BBC does it, why don't you? It's really, REALLY not hard to do.
    Now put it in the article and prove you have a lick of competent science reporting.

    April 14, 2011 at 11:15 pm | Report abuse |
    • Andrew

      Well, now that the original paper has been linked, I really can't complain. I love seeing the original sources get listed.

      April 14, 2011 at 11:56 pm | Report abuse |
  14. cnnot

    here's an interesting theory, back in the dinosaur days they all ate at McDonalds and didn't have to go hunt at all.

    April 14, 2011 at 11:15 pm | Report abuse |
  15. Polaris

    I wonder what dinosaur in Congress gave thes scientists a grant to come up with this...just another waste of taxpayer dollars. Time to put the old dinosaurs in Congress on the extinct list.

    April 14, 2011 at 11:18 pm | Report abuse |
    • amphiox

      Firstly, we do not know how much of the funding for this research came from government (ie taxpayer) sources.

      Secondly, the acquisition of knowledge is NEVER a waste of money.

      Thirdly, the amount of money required to conduct research such as this is about equal to what would be spent in ONE MINUTE of battle action in Iraq or Afghanistan. So what is the waste again?

      April 15, 2011 at 1:53 am | Report abuse |
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