The Dynamic Diet of Dinosaurs

According to Dr. Jordan Mallon, paleontologist and research scientist at Canadian Museum of Nature, dinosaurs had varying diets: some ate plants, some ate meat, and some ate both, but most were actually plant eaters. 

“If every dinosaur were a meat eater, their environment would be unable to support them,” he says. “You need your herbivores feeding on ferns or other plants and your carnivores going after the herbivores.” 

As Dr. Mallon explains, dinosaurs, like all species that have roamed the earth, had to adapt to fill different niches in their environment in order to take advantage of all the ecological opportunities available. 

Over the course of the dinosaurs’ reign, some carnivorous dinosaurs did evolve to become herbivorous or omnivorous. But for herbivores it was harder to make that switch because of how specialized their digestive systems were, says Dr. Donald Henderson, a paleontologist and curator of dinosaurs at the Royal Tyrrell Museum of Palaeontology (RTMP) in Alberta. 

“The plant eaters have always outnumbered carnivores in any ecosystem,” Dr. Henderson says, adding that most dinosaurs were herbivores because of how abundant plant life is.  

Many plants we see today were eaten by herbivorous dinosaurs. Soft and spongy moss, spindly and fragrant pine trees, and Ginkgo biloba, one of the oldest living tree species in the world, made it onto their plates. 

Dinosaurs like Stegosaurus, Triceratops, Ankylosaurus, and hadrosaurs (duck-billed dinosaurs) dined on plants. In fact, paleontologist Dr. Albert Prieto-Márquez found that some hadrosaurs survived primarily on pine trees. 

However, being a herbivore was not without its difficulties. Dr. Mallon says that while being a herbivore was advantageous because you never had to catch your prey—“they’re always standing still”—most plant cells have a feature that animal cells don’t have: a cell wall. This makes plants hard to digest. 

As a response, many herbivorous dinosaurs had to evolve various ways of circumventing plant defenses, such as specialized teeth and broader guts. And some swallowed gizzard stones to help with digestion. 

Meat, on the other hand, was considerably easier to digest. While some carnivorous dinosaurs feasted on lizards, turtles, early mammals, and dead animals, others like the hulking Tyrannosaurus rex also went after living herbivorous and carnivorous dinosaurs.  

“A dinosaur like T. rex was likely at the top of the food chain so it wouldn’t be going after small animals which were no bigger than rats or cats at the time, you know?” says Dr. Philip Currie, a paleontologist who helped found the RTMP. 

“It makes sense that it went after big animals and other types of dinosaurs,” he adds.  

According to Dr. Mallon, paleontologists have even found a hadrosaur bone with a broken T. rex tooth in it. The bone had also healed around the tooth, revealing that T. rex hunted this dinosaur while it was still alive. 

Sauropod bones have also been discovered in the western United States with tooth marks from an Allosaurus (a top carnivore like T. rex) on it, recalls Dr. Henderson.  

As Dr. Currie puts it, “it was a dog-eat-dog world.” 

Some dinosaurs even ate insects, fish and crustaceans—including the herbivorous dinosaurs, indicating that even the plant-eating dinosaurs mixed things up.  

Everyone's favourite anthropomorphic fictional dinosaur, Barney the T. rex, had an unusual diet: His favourite food was a peanut butter and jelly sandwich with a glass of milk.  

Barney’s dinosaur friends—Baby Bop, a ballet-dancing Triceratops and BJ, a basketball-playing Protoceratops—were partial to an ice cream sundae. 

Peanut butter was not accessible in the Age of the Dinosaurs and neither were unlimited sundae toppings, but that didn't stop some dinosaurs from making interesting dietary choices, like the plant-eating dinosaurs that ate rotting wood. 

Whether the menu listed decaying wood or decaying flesh, Dr. Mallon says that at the end of the day the choice different dinosaurs made usually came down to two main reasons: “their environment and their evolutionary ancestry.”  

And while they were here, their choices seemed to have served them well. 

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Learn more about the dino-mite life of the T. rex.

Our current feature exhibition, T. rex: The Ultimate Predator, presented by RBC and White Spot Restaurants, takes visitors back in time to encounter the prehistoric wonders of the late Cretaceous period and come face-to-face with a 66-million-year-old marvel!