T-rex: Babykiller? or Tank Buster?

The two most famous prehistoric combatants T-rex and Triceratops (Fig. 1), face off time and again in Charles Knight paintings and in the imaginations of every Montana paleontologist and grade-school kid. It’s worth a Google search of these two to see some really terrific recent iterations.

A recent challenge to this notion comes from Hone and Rauhut (2009) who conclude, “like modern predators, theropods preferentially hunted and ate juvenile animals leading to the absence of small, and especially young, dinosaurs in the fossil record.”

That’s an intriguing possibility. Doesn’t make such a dramatic painting or cartoon, and does this one behavior really reflect a lack of young dinosaurs in the fossil record?

From the perspective of an artist,
there’s a bit more to this picture that needs to be considered. What’s missing from the Knight painting (Fig. 1) are dozens more Triceratops of all ages and genders. Where’s the rest of the herd? They’re missing from the painting for two reasons, one dramatic and one practical.

The dramatic moment of the painting comes down to “man-to-man” here, “life or death” focusing the plight and fight on only these two combatants. Which will win? The backstory we don’t see is, how did this rogue bull Triceratops get separated from his herd?

The practical aspect, from an artist’s perspective, is the reduction to a one-on-one combat greatly simplifies not only the story line, but the layout and the amount of time needed to complete the painting. A working artist is successful when he can produce the most for the least and Knight produced THE iconic dinosaur painting of all time with just three characters.

The reality of the actual Late Cretaceous scene might have been more similar to a German wolfpack of U-boats surrounding an Allied flotilla, patiently waiting for the cover of night or the revelation of which herd member was lame, stuck in a muddy riverbank or protecting one too many juveniles. One downed prey Trike would have fed several pursuing tyrannosaurs.

Paul (2010) makes the point, “healed wounds on adult hadrosaurs and ceratopsids indicate that [T-rex] adults hunted similarly elephant-sized prey on a regular basis, using the tremendous head and teeth to lethally wound victims, such firepower and size was more than needed to hunt less dangerous juveniles.”

I’ll make the obvious point, reiterating Hone and Rauhut (2009), if every meal was a life-or-death scene for T-rex, very few would have survived to adulthood. For every meal that T-rex considered, it had to attack only those that offered the least risk and most reward.

Let’s also remember that juvenile T-rex did not have the firepower that robust adults had. Did juveniles pick off the smaller easier prey? Or did they follow in the footsteps of more powerful adults who provided to them already subdued prey? Or bits and pieces thereof?

Rauhut reports, “Juvenile dinosaurs are surprisingly rare – maybe because many of them have been eaten by predators.” Of course, juvenile dinosaur (including predatory dinosaur) fossils might be so rare because they grew up to become adults.

What about hadrosaurs?
It’s also instructive to Google search for hadrosaur + t-rex to see absolutely NO similar scenes involving hadrosaur fights. Clearly the dramatic moment with hadrosaurs cannot match the dramatic moment with horns and frills. If hadrosaurs were just slightly faster than giant theropods, they could have outrun them, unless the tyrannosaurs hunted cooperatively. Or were hadrosaurs just so easy to kill that the occasional attack against a Triceratops was born of desperation?

Alright, so, without our handy time machine, we’ll probably never know, but it seems the correct solution is an opportunistic combination of the two hypotheses, regulated by the age and health of the combatants. Artists will continue to portray T-rex and Triceratops as simply and economically as possible. The reality, pathos and chaos of the actual battle scene, filled with chicks, hens and bulls on both sides, changing meal to meal, day to day and year to year, will probably remain just out of reach of our most fertile imagination. Let’s not a priori mentally exclude all the possibilities before coming to conclusions.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Hone DWE and Rauhut OWM 2009. Feeding behaviour and bone utilization by theropod dinosaurs. Lethaia online, 3 August 2009.
Paul G 2010. The Princeton Field Guide to Dinosaurs. Princeton University Press, 320 pp.

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