Juvenile Tyrannosaurs and the Mystery of Dinosaur Diets
Season 1 Episode 11 · Whimsical Wavelengths
Episode overview
How do scientists reconstruct the behavior of animals that have been extinct for more than 65 million years? In this episode of Whimsical Wavelengths, geophysicist Jeffrey Zurek speaks with François Therrien, curator of dinosaur paleoecology at the Royal Tyrrell Museum, about an extraordinary fossil discovery that provides a rare window into the lives of young tyrannosaurs.
The conversation centers on a remarkably preserved juvenile Gorgosaurus libratus skeleton containing fossilized stomach contents—two small theropod dinosaurs preserved inside the rib cage. Published in Science Advances, this discovery reveals an unexpected dietary strategy in young tyrannosaurs and demonstrates how feeding behavior changed dramatically as these iconic predators grew.
Along the way, the episode explores how paleontologists interpret behavior from fossils, how ecosystems at the end of the Cretaceous were structured, and why tyrannosaurs in North America filled ecological niches unlike anything seen in modern ecosystems.
Listen to the episode on Apple here
Or
Listen to the episode on Spotify here
What this episode covers
-
How paleontologists infer behavior from fossil evidence
-
The discovery of preserved stomach contents in a juvenile Gorgosaurus
-
What an “ontogenetic dietary shift” means in evolutionary biology
-
Why young tyrannosaurs ate differently than adults
-
Evidence for selective feeding on the meatiest parts of prey
-
How prey abundance shapes predator behavior
-
Why North American tyrannosaur ecosystems were unusual
-
Comparisons between dinosaur ecosystems and modern predators
-
The role of CT scanning, synchrotron imaging, and AI in paleontology
-
Why most scientific work is slow, meticulous, and rarely glamorous
Why this discovery matters
Tyrannosaurs are often imagined as single-minded apex predators, but this fossil tells a more nuanced story. The juvenile Gorgosaurus examined in this study was between five and seven years old—large, powerful, and capable of hunting—yet it did not consume entire carcasses. Instead, it selectively ate the hind legs of two much smaller dinosaurs, swallowing them whole and leaving the rest behind.
This behavior suggests a combination of prey abundance, energetic efficiency, and ecological opportunity. Understanding these patterns helps scientists reconstruct ancient food webs, population dynamics, and how predators avoided competition by changing diets as they grew. It also shows that tyrannosaurs didn’t simply “become” apex predators overnight—they grew into that role.
The fossil: a juvenile Gorgosaurus libratus
This specimen represents the most complete juvenile tyrannosaur skeleton ever discovered in North America. During preparation at the Royal Tyrrell Museum, technicians uncovered tiny bones emerging from within the rib cage—far too small to belong to the Gorgosaurus itself.
Further preparation revealed the articulated hind legs of two small theropods (Citipes), preserved inside the stomach cavity. The condition of the bones showed they were swallowed whole, without crushing, providing direct evidence of feeding behavior rather than scavenging or coincidence.
Key concepts explained
Ontogenetic dietary shifts
“Ontogenetic” refers to changes that occur as an organism grows. In tyrannosaurs, this meant transitioning from hunting small, agile prey as juveniles to attacking large herbivores as adults. This episode shows how fossil evidence captures that transition in action.
Selective feeding
Rather than consuming entire prey animals, young tyrannosaurs targeted the most energy-rich parts—the hind limbs. This strategy mirrors modern predators that take advantage of abundant food sources when risk is low and energy efficiency is high.
Ecosystem structure
In Late Cretaceous North America, tyrannosaurs occupied multiple ecological niches throughout their lives. Juveniles filled the roles of mid-sized predators, while adults dominated the apex niche—an arrangement unlike most modern ecosystems.
Seasonal abundance and predator behavior
The episode explores the idea that prey availability may have been seasonal, similar to modern salmon runs. Citipes likely laid large clutches of eggs, producing an abundance of young dinosaurs across the landscape. For juvenile tyrannosaurs, this may have created brief windows of plentiful, low-risk food—making selective feeding both possible and advantageous.
Technology and the future of paleontology
Beyond the fossil itself, the discussion broadens to how paleontology is changing. François Therrien explains how CT scanning and synchrotron imaging allow scientists to study internal bone structures without damaging fossils. Artificial intelligence is increasingly used to automate tedious tasks like segmenting CT scan images, freeing researchers to focus on interpretation rather than manual data processing.
These tools are transforming paleontology from a largely descriptive science into a more quantitative and computational discipline.
The reality of scientific work
A recurring theme in the episode is the contrast between how science is portrayed and how it actually unfolds. Fossil discoveries are rare; most of the work involves careful preparation, data analysis, and long hours of meticulous effort. The episode reflects on how patience, specialization, and teamwork are essential—and why loving science often means loving its slowest parts.
Frequently asked questions
What did young tyrannosaurs eat?
They primarily hunted small animals and juvenile dinosaurs, often selecting specific parts rather than consuming entire carcasses.
Why didn’t they eat the whole animal?
High prey abundance and lower competition likely made selective feeding more efficient than full consumption.
What makes North American tyrannosaur ecosystems unusual?
Tyrannosaurs filled multiple predator roles throughout their lives, leaving few niches for other mid-sized predators.
How do scientists know what dinosaurs ate?
Direct evidence like stomach contents, tooth marks, and bone damage—combined with modern imaging techniques—allows detailed behavioral interpretations.
Episode context
This episode continues Whimsical Wavelengths’ focus on how science actually works: incomplete data, careful inference, and the gradual refinement of ideas. It highlights how a single fossil can reshape long-standing assumptions and how interdisciplinary tools—from geology to AI—contribute to understanding deep time.
Episode details
Podcast: Whimsical Wavelengths
Season: 1
Episode: 11
Format: Interview
Category: Paleontology · Evolution · Earth Science · Science Research
Enjoyed this episode?
Subscribe to Whimsical Wavelengths on your favorite podcast platform, leave a review, or share this episode with anyone curious about dinosaurs, ecosystems, or how scientists turn fragments of bone into stories about ancient lives.
