Unlike Jurassic Park, real raptors may not have hunted in packs

New research suggests director Steven Spielberg used just a little bit of creative license when making Jurassic Park.

While the coordinated attacks of Velociraptor dinosaurs depicted in the 1993 blockbuster made for compelling movie viewing, a new study -- published this week in the journal Palaeogeography, Palaeoclimatology, Palaeoecology -- claims raptors most likely hunted solo, not in packs.

"Raptorial dinosaurs often are shown as hunting in packs similar to wolves," Joseph Frederickson, a vertebrate paleontologist and director of the University of Wisconsin's Weis Earth Science Museum, said in a news release. "The evidence for this behavior, however, is not altogether convincing. Since we can't watch these dinosaurs hunt in person, we must use indirect methods to determine their behavior in life."

According to Frederickson, the closest living relatives of dinosaurs, birds and crocodiles, don't hunt in packs nor target prey larger than themselves. What's more, evidence of coordinated hunting doesn't fossilize.

For the new study, Frederickson and his colleagues set out to identify similarities between the diet and hunting practices of raptors and Komodo dragons or crocodiles.

"We proposed in this study that there is a correlation between pack hunting and the diet of animals as they grow," Frederickson said.

When they're young, Komodo dragons are at risk of predation by adults. To protect themselves, baby Komodo dragons hide high in trees. Up in the canopy, these young dragons take advantage of a range of food sources not utilized by their older relatives.

According to authors of the new study, this dietary divergence is not seen in animals that hunt in packs.

"If we can look at the diet of young raptors versus old raptors, we can come up with a hypothesis for whether they hunted in groups," Frederickson said.

Researchers analyzed the teeth of Deinonychus raptors, which roamed North America between 115 and 108 million years ago.

"Stable isotopes of carbon and oxygen were used to get an idea of diet and water sources for these animals," Frederickson said. "We also looked at a crocodilian and an herbivorous dinosaur from the same geologic formation."

Their analysis revealed a divide between the isotopic composition of older and younger teeth, suggesting the raptors altered their diet as they matured.

"This is what we would expect for an animal where the parents do not provide food for their young," Frederickson said. "We also see the same pattern in the raptors, where the smallest teeth and the large teeth do not have the same average carbon isotope values, indicating they were eating different foods. This means the young were not being fed by the adults, which is why we believe Jurassic Park was wrong about raptor behavior."

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