Why do predatory dinosaurs have eyes on the sides of their head?
This week's question comes to us from Graham Richard from Haida Gwaii, who asks the following:
Eye orientation can reveal a lot about the niche terrestrial vertebrates occupy. Eyes of predators like mountain lions and pine martens have forward-facing eyes, whereas herbivores like Sitka deer or chipmunks tend to have eyes that are oriented temporally. This provides predators with greater depth-perception for pouncing on food, and gives prey a wider view of the landscape to survey the many dangers that may lurk just beyond their view.
Richard wants to know why predatory dinosaurs appear to have eyes on the sides of their head?
François Therrien, the Curator of Dinosaur Palaeoecology at The Royal Tyrrell Museum in Drumheller, Alberta, says that most meat-eating dinosaurs known as theropods, had laterally positioned eyes, but not all of them. Having eyes on the sides of their heads resulted in a limited amount of depth perception, similar to pigeons and crocodiles today. This was not ideal for locating prey. But theropods, including tyranosaurs such as the famous T-rex, had forward-facing eyes. This gave them a high degree of binocular field of view. This means that tyrannosaurs would have had excellent depth perception to estimate the distance to prey and the timing of their attack. Their vision was similar to today's falcon. It also means that T-rex would have been able to detect prey even if it stood still against the background. So Jurassic Park got it wrong! Smaller theropods, like Velociraptor and Troodon, had even better depth perception than T-rex. Their vision was similar to that of modern owls.