25 June 2015

Leader of the pack: fleshing out Velociraptor behaviour in Jurassic World

“Do we know Velociraptors were pack hunters, or did the filmmakers just make that up?”

That question came up on the Nature “Backchat” podcast during discussion of Jurassic World. None of participants had a good answer, so here’s mine.

The first thing you have to understand is that the Velociraptor in Jurassic Park / Jurassic World is not the Velociraptor that actually lived. It’s Deinonychus in disguise.

It’s a shame that Velociraptor has stolen the thunder from Deinonychus. It’s hard to underestimate how important Deinonychus was to our current conception of dinosaurs. When Ostrom (1969) published his description of Deinonychus, people were still showing sauropods in the swamps and lakes. Dinosaurs were sluggish lizards.

The description of Deinonychus blew those ideas of dinosaurs out of the water. The claw on the legs was the feature that led Ostrom to suggest that Deinonychus must have been an agile, active hunter. The claw only made sense as a slashing appendage.

The frontispiece of the description is this reconstruction by Bob Bakker (who would go on to be a major proponent of “hot blooded” dinosaurs):

Badass, right?

And not at all far from what you see in Jurassic World! The main difference is that Ostrom estimated Deinonychus stood about one meter high, and was maybe three meters from nose to tail. It’s a lot smaller than the Jurassic World beasts.

Here’s where the idea of theropods as pack hunters all started, on page 144 of Ostrom’s monograph:

(A)t least three and perhaps four or five individuals are represented among the Deinonychus remains collected from just a small area at the Yale site. These remains were associated with fragments of only one other species — a moderate-sized ornithopod that weighed perhaps five or six times as much as Deinonychus. The multiple remains of the latter suggest that Deinonychus may have been gregarious and hunted in packs.

(Ornithopods, incidentally, are big herbivores like Iguanadon.)

 So Jurassic Park did not just pull the idea of pack hunting dinosaurs out of nowhere. It was a serious suggestion made by a proper scientist in the scientific literature.

For some reason, when Michael Crichton wrote the book Jurassic Park, he took that idea of Deinonychus as pack hunters and applied it to velociraptors. I’m guessing that the reason he did this was so he could call them “raptors,” which people knew as birds of prey. Crichton was very big on emphasizing the relationships between birds and dinosaurs. It comes up over and over again in the book, and was carried through to the movie. (When I rewatched Jurassic Park in the last month in preparation for Jurassic World, the “just like birds” didactic dialogue felt the most dated.)

Crichton’s decision was weird, though, because velociraptors were, um, way less badass than Deinonychus:

Velociraptors were pretty small. (Dan Telfer does a hysterical riff about this in his stand-up routine, “The best dinosaur.”)

When Steven Spielberg made Jurassic Park, he thought even Deinonychus was too small and made his theropods bigger than any that had been found at the time. He was vindicated, however: the same year, a Jurassic Park-sized dinosaur called Utahraptor was described (Britt et al. 1993).

A year later, Ostrom gave a talk where he described Deinonychus as “the ultimate killing machine,” which suggests he was still on board with the portrayal of theropods in Jurassic Park.

How has the pack hunting hypothesis held up since 1969? Maybe not that great. Roach and Brinkman (2007) reevaluated the pack hunting idea:

(W)e conclude that this hypothesis is both unparsimonious and unlikely for these taxa(.)

Sigh. There you go again, science, wrecking childhood dreams! Years from now, we’ll get adults saying, “What do you mean, raptors weren’t pack hunters?!” with the same indignation that we’ve seen over the loss of Pluto or Brontosaurus as names. (Though we might have gotten bronto back!)

The portrayal of pack hunting meat eating dinosaurs is so entrenched now that we’ll probably get movies showing us feathered theropods before we get solitary ones.

Update: Anthony Martin pointed out that there has been some more evidence on theropod group behaviour. A 2008 paper by Li and colleagues found six sets of footprints of Deinonychus-like animals, running in parallel and closely spaced, apparently made simultaneously.

They interpreted this as evidence for group behaviour. For instance, that they are parallel suggests that these weren’t just six animals walking along in the same direction because of some physical feature in the landscape. Then, the tracks might go in the same direction, but overlap when one animal walked behind another.

Of course, this doesn’t prove pack hunting. The fossil you’d want to find would be one big animal buried with a few theropods with their claws embedding in the prey’s body. Maybe that fossil exists, still waiting for someone to dig it up...


Britt B, Chure D, Stadtman K, Madsen J, Scheetz R, Burge D. 2001. New osteological data and the affinities of Utahraptor from the Cedar Mountain Fm. (Early Cretaceous) of Utah. Journal of Vertebrate Paleontology 21: 1-117. DOI: 10.1080/02724634.2001.10010852

Li R, Lockley M, Makovicky P, Matsukawa M, Norell M, Harris J, Liu M. 2008. Behavioral and faunal implications of Early Cretaceous deinonychosaur trackways from China. Naturwissenschaften 95(3): 185-191. DOI: http://dx.doi.org/10.1007/s00114-007-0310-7

Ostrom JH. 1969. Osteology of Deinonychus antirrhopus, an unusual theropod from the lower Cretaceous of Montana. Bulletin of the Peabody Museum of Natural History 30:1–165.

Ostrom JH. 1994. Deinonychus, the ultimate killing machine. In: Rosenberg GD, Wolberg DW, editors. eds. Dino Fest: proceedings of a conference for the general public, March 24, 1994. Knoxville, TN University of Tennessee, Department of Geological Sciences. pp. 127137. (The Paleontological Society, Special Publication 7.).

Roach BT, Brinkman DL. 2007. A reevaluation of cooperative pack hunting and gregariousness in Deinonychus antirrhopus and other nonavian theropod dinosaurs. Bulletin of the Peabody Museum of Natural History 48(1):103-138. DOI: http://dx.doi.org/10.3374/0079-032X(2007)48[103:AROCPH]2.0.CO;2

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