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Pasha and Marius are at completely different junctures in their careers. Pasha van Bijlert's undergraduate research focused on the preferred speed of the Tyrannosaurus rex – his conclusions were quoted by media including NPO1, CNN and Reuters. He is currently pursuing a PhD in Geosciences. As a part of his research on movement, Van Bijlert creates 3D biomechanical models of various animals. The resulting movement models can then be applied to Tyrannosaurus rex. As a veterinarian, Marius Dwars observed the evolution of the poultry industry from up close. Having started his career at the Poultry Health Service in Doorn, he found his way to the Faculty of Veterinary Medicine where he taught for almost 40 years before retiring. His classes on chickens contained frequent references to dinosaurs. So what can movement teach us about behaviour? What can living animals teach us about extinct ones?

Most animal behaviour is rooted in movement. How can your 3D motion models of living animals help us gain a better understanding of Tyrannosaurus rex?

Pasha: "My PhD research over the next four years will focus on physics simulation models of different animal species. That includes elephants, horses (in collaboration with veterinary researcher Filipe Serra Bragança and PhD candidate Ineke Smit), humans, ostriches and a few smaller bird species. These simulation models have a wide range of applications: for example, you can use them for human-animal diagnostics, but they can also be applied to dinosaurs. I should point out that this isn't a "dinosaur project." It's more of an "animal-movement project" that also happens to involve dinosaurs."

A T. rex's mobility will change over the course of its lifespan, affecting its behaviour and hunting strategies. You can explain a lot on the basis of skeletons, which I aim to focus on over the coming period. Still, if you want to find concrete answers about behaviour, you can't exclusively rely on fossil skeletons.

I used to refer to dinosaurs a lot during my classes on chickens.

Dinosaur bones tend to have bite marks. They even found a rival's tooth in a T. rex jaw. So what does that tell us about the T. rex's hunting behaviour?

Pasha: "The nice thing about bite marks is that we now know multiple dinosaurs were bitten by a T. rex. Interestingly enough, many of those wounds also eventually healed: that tells you that this animal was hunted and caught by a T. rex, but ultimately survived. It also tells us those wounds eventually healed and the animal hopefully lived a long life before it died."

“Research has shown that T. rex individuals also frequently bit each other's faces. You could interpret that in several ways: it could be the result of a clash with a rival, it could have happened during mating, or both. We have clear evidence of facial bites, and while they're definitely indications of behaviour, we still don't know the causes of that behaviour."

Dinosaurs appeal to a broad audience, and that includes students. So how did you manage to work dinosaurs into your classes on chickens?

Marius: "In the words of palaeontologist Jelle Reumer: "hummingbirds are the pinnacle of creation". Birds are dinosaurs and that includes chickens. Air sacs and skeletal pneumatics (the presence of air in bones) originated in dinosaurs and evolved in birds."

"I used to refer to dinosaurs a lot during my classes on chickens. I wanted to challenge my students to see the 'ordinary' chicken in a different light. I'd tell them: "Do you realise this is an actual dinosaur we're dealing with here?". I was trying to get them to see things from a different perspective.

According to my simulations, the Tyrannosaurus rex has a top speed of 30 km/h, which is very fast for an animal weighing 7800 kg.

You can't just go around attributing behavioural traits to extinct species. So which behavioural traits have we wrongly attributed to T. rex?

Pasha: “Tyrannosaurus rex is known as a huge, charismatic carnivore: a hypercarnivore. That notion is reflected in all the imagery: a triumphant creature roaring with its jaws wide open or chasing prey at full speed. In reality, there's no way they could ever have run fifty km/hour. "According to my simulations, the Tyrannosaurus rex has a top speed of 30 km/h, which is very fast for an animal weighing 7,800 kg." You don't tend to see images of them sitting around, or just drinking some water – most predators spend most of the day doing absolutely nothing. But that's obviously less interesting in visual terms."

Humans created broilers and laying hens in order to maximise production. Do these chickens behave any differently from the ones we had 70 years ago?

Marius: "The chicks we farm today gain a lot of muscle really quickly, which increases mechanical forces on the skeleton. They're subjected to forces they'd never encounter in nature. As a result, the animal becomes disproportionately heavy and its centre of gravity shifts forward a lot. That affects aspects like their sense of balance, as you notice when the chickens try to turn around. If you compare a chicken from 1965 to the ones we have today, today's chickens are basically a 'work of art' created by humans."

"The combination of rapid growth and short breeding times has ended up making it more difficult for the animals to walk, which raises all kinds of issues. The poultry industry will need to monitor the situation and intervene if the animals end up suffering as a result. We also need to make sure the animals don't grow too much in too little time."

Do you have any tips for lecturers looking to incorporate dinosaurs in their veterinary education?

Marius: "Dinosaurs are a great way to spark debate, but lecturers could also use them to illustrate primal mechanisms. Some physiological functions, ratios and skeletal structures are more than a hundred million years old."

"If you take that comparison too far you quickly end up in the realm of anatomy, and the extent to which chickens differ from mammals. You'll lose the students' attention, so the extra information won't do much good. Just add a sprinkling of dinosaur to spice things up. Think of them as a kind of hot sauce."

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