Her deadly teamwork has made her famous: In films like “Jurassic Park”, the so-called raptors are portrayed as social predators, who hunted in a pack like wolves. But what is it about this image? Paleontologists are now questioning it because, according to them, indications of nutritional differences between young and adult animals are more against the thesis of the Cretaceous pack animal.
In addition to Tyrannosaurus rex and Co, they have caused a lot of tension in the cinema: the so-called raptors. They are representatives of the dinosaur group of the dromaeosaurids – medium-sized predatory dinosaurs walking on the hind legs. The up to 3.4 meter long Deinonychus antirrhopus, which belonged to the subgroup of Velociraptorinae, served as the model for the terrifying film stars. It is already clear that one feature of the raptors was always misrepresented in the films: they were not naked or covered with scales. Because probably all Dromaeosauriden had a plumage, as is known from numerous finds.
Speculations about pack behavior
But what about the behavior that shapes the role of the raptors in the films? “Since we cannot observe these dinosaurs while hunting, we have to use indirect methods to draw conclusions about their behavior,” said Joseph Frederickson from the University of Wisconsin in Oshkosh. “The clues as to what these predatory dinosaurs hunt in the pack are only vague,” emphasizes the paleontologist. Finds of fossilized specimens have so far been regarded as evidence of appropriate behavior. Petrifications of traces of the predatory dinosaurs that run side by side were also considered as evidence that the raptors lived in groups and possibly hunted together.
However, as Frederickson and his colleagues explain, there are other causes for these finds. Basically, they point out that the hunting behavior in the pack is typical for some mammals, but not for the closest relatives of the raptors still alive today – the birds. In their study, the scientists now clarify that it is also possible that the predatory dinosaurs behaved similarly to today’s Komodo dragons or crocodiles: Often, several specimens of these animals attack a victim at the same time, but this does not lead to complex cooperation such as in a pack.
Behavior in the mirror of isotope analyzes
“As part of our study, we are now showing that there is a link between the pack hunting behavior of animals and their diet during their development,” says Frederickson. At Wolf and Co, adult animals bring their young to the hunt – so all ages in principle feed on the same food. In the case of Komodo dragons or crocodiles, on the other hand, the young are not fed, but look for their own, mostly smaller prey animals. This clearly differentiates their food from that of adult animals, the scientists explain.
In order to draw conclusions about the behavior of the raptors, they have now carried out chemical analyzes of fossil teeth of young and older specimens of Deinonychus. As they explain, a living being’s diet leaves characteristic traces in its material when teeth grow. Comparisons of the isotope signatures of carbon and oxygen thus allow conclusions to be drawn as to whether the menu varied between young and old specimens.
As Frederickson and his colleagues report, the results of the investigation showed that, similar to crocodiles, there was a difference in diet among the raptors between the young and the adult animals. This could reflect that these predatory dinosaurs did not bring any food to their offspring, as is common in today’s animals with social hunting behavior. “That’s why we believe that the representation of the behavior of the raptors in Jurassic Park is not realistic,” concludes Frederickson. The fearsome Velociraptor and his relatives may have shown less sophisticated hunting behavior than Hollywood depicts.
Source: University of Wisconsin at Oshkosh, technical article: Palaeogeography, Palaeoclimatology, Palaeoecology, doi: 10.1016 / j.palaeo.2020.109780