Triceratops was a plant-eater, and most of what it ate was tough, fibrous vegetation. Its mouth worked like a cutting tool, with a sharp beak up front and teeth intricate enough to rival those of mammals.1PubMed Central. Wear biomechanics in the slicing dentition of the giant horned dinosaur Triceratops Much of what we know about its diet comes from reading those teeth and jaws, backed by a few rare traces of what it actually swallowed.
The Plants on the Triceratops Menu
Most Triceratops fossils come from the Hell Creek Formation, a stack of rocks in Montana and the Dakotas laid down about 66 million years ago. Fossil leaves from the base of the Hell Creek rocks show flowering plants made up 13 of 17 plant types found.2Through the End of the Cretaceous in the Type Locality of the Hell Creek Formation in Montana and Adjacent Areas. A florule from the base of the Hell Creek Formation in the type area of eastern Montana: Implications for vegetation and climate Another site from the same era shows forests dominated by flowering trees, with plenty of conifers and fewer ginkgoes and ferns.3Cretaceous Research. Seafood Salad: A diverse latest Cretaceous flora from eastern Montana Plant communities differed from place to place and shifted quickly, so one herd’s menu could differ from another’s.4Cretaceous Research. Seafood Salad: A diverse latest Cretaceous flora from eastern Montana
That count needs careful reading. It measures variety, meaning how many kinds of plant were present, and says nothing about how much ground flowering plants covered. Leaves also fossilise best where they fell into mud near ponds and rivers, so the record is a good but incomplete sample of the landscape. Scientists therefore say flowering plants were diverse, and that Triceratops eating them is an inference.
These were not the gardens or lawns you might picture. Cretaceous flowering plants were mostly broadleaf shrubs and trees. Grass was not yet a common food, so Triceratops was not a grazer like a cow.
Triceratops ate a wide range of what grew around it:
- Flowering plants: likely most of its diet.5Redpath Museum. A triceratopsian diet
- Ferns and palms: growing near the ground.6Extinct Atlas. What Did Triceratops Eat? Diet, Teeth, and Feeding Behaviour Explained
- Cycads: stiff, palm-like plants with tough leaves.7Extinct Atlas. What Did Triceratops Eat? Diet, Teeth, and Feeding Behaviour Explained
- Conifers: relatives of today’s pines.8Extinct Atlas. What Did Triceratops Eat? Diet, Teeth, and Feeding Behaviour Explained
- Other parts: possibly fruits, seeds, twigs and roots as well as leaves.9Redpath Museum. A triceratopsian diet
Fibrous, tough vegetation likely formed most of the menu.10Extinct Atlas. What Did Triceratops Eat? Diet, Teeth, and Feeding Behaviour Explained
How Its Beak and Teeth Handled Tough Plants
The front of the mouth was a toothless, parrot-like beak used to grab and clip plants. Its edge stayed useful because it was a hard keratin sheath, the same material as a fingernail or a bird’s bill. But beaks alone can do little to break food down,11PubMed Central. The coevolution of rostral keratin and tooth distribution in dinosaurs so the chopping happened further back, in the cheek teeth.
Those cheek teeth were packed into stacked rows that formed one long cutting edge.12PubMed. Incremental lines of von Ebner in dinosaurs and the assessment of tooth replacement rates using growth line counts Each tooth position held several teeth, one behind another, so a worn tooth was always backed up by a fresh one below.
During feeding, the teeth wore into blades with a hollowed centre that reduced friction.13PubMed Central. Wear biomechanics in the slicing dentition of the giant horned dinosaur Triceratops That happened because each tooth was built from five tissues that wore at different speeds.14PubMed Central. Wear biomechanics in the slicing dentition of the giant horned dinosaur Triceratops Enamel, the hardest and slowest-wearing, wore about six times more slowly than the softest tissue.15PubMed Central. Wear biomechanics in the slicing dentition of the giant horned dinosaur Triceratops So the harder tissues stayed as raised cutting edges while softer tissue wore into a basin.16PubMed Central. Wear biomechanics in the slicing dentition of the giant horned dinosaur Triceratops The result suited fracturing the toughest plant tissues.17PubMed Central. Competition structured a Late Cretaceous megaherbivorous dinosaur assemblage
This is slicing, not grinding. Cows and horses grind side to side with flat molars, while Triceratops cut with a scissor-like up-and-down action. Slicing suits stiff, fibrous plants better than soft leaves. Huge muscles anchored under the frill powered the bite, enough to cut woody stems and even small trees.
All that rough chewing wore teeth down fast.18PubMed. Incremental lines of von Ebner in dinosaurs and the assessment of tooth replacement rates using growth line counts Triceratops kept replacing them quickly throughout its life.19PubMed. Incremental lines of von Ebner in dinosaurs and the assessment of tooth replacement rates using growth line counts
How High a Triceratops Could Reach
Its short front legs tilted the head toward the ground, which suited low-growing plants.20Extinct Atlas. What Did a Triceratops Eat? Diet, Teeth, and Feeding Behaviour Explained A heavy skull and frill also made it costly to hold the head high for long, so the head hung low when it stood normally. Horned dinosaurs most likely browsed no higher than about 1 metre, roughly hip height on an adult person.21PubMed Central. Feeding height stratification among the herbivorous dinosaurs from the Dinosaur Park Formation (upper Campanian) of Alberta, Canada Even one of the largest Triceratops known could not reach above 1.2 metres.22PubMed Central. Feeding height stratification among the herbivorous dinosaurs from the Dinosaur Park Formation (upper Campanian) of Alberta, Canada It could tilt its head up somewhat to reach a little higher.23Extinct Atlas. What Did a Triceratops Eat? Diet, Teeth, and Feeding Behaviour Explained
Some older claims gave it a 2-metre reach with no real evidence. Low feeding was no weakness. Ferns, cycads and shrubs grew thickly near the ground, and feeding there left taller plants to other dinosaurs, much as a rhino does today.
For higher food, Triceratops may have eaten whole trees, trunk and all.24Redpath Museum. A triceratopsian diet It likely pushed over or broke saplings to bring the leaves within reach.
How Scientists Know What Triceratops Ate
A nearly complete Triceratops skeleton from Montana kept fossilised plant remains inside its gut cavity.25Geological Society of America Abstracts with Programs. Surprising Preservation of Herbivorous Dinosaur Gut Contents Through Replacement With Clay The remains form a layer about 3.5 cm thick of finely chopped plant tissue.26Geological Society of America Abstracts with Programs. Surprising Preservation of Herbivorous Dinosaur Gut Contents Through Replacement With Clay That matches what the teeth suggest: the plants were cut into small pieces before swallowing.
Stomach contents normally rot within days, so preserving them takes quick burial, here in river sand. Some plant tissue was replaced by clay, which preserved it.27Geological Society of America Abstracts with Programs. Surprising Preservation of Herbivorous Dinosaur Gut Contents Through Replacement With Clay The clay kept cell outlines visible after the original material had gone, and scientists examined the bits under magnification to see how finely they had been cut. A single find confirms the picture but cannot show everything the animal ate.
Tooth chemistry adds another clue. Carbon in tooth enamel records the plants an animal ate, since different plants leave slightly different carbon signatures, and oxygen records the water it drank.28Paleobiology. Stable isotope evidence for changes in dietary niche partitioning among hadrosaurian and ceratopsian dinosaurs of the Hell Creek Formation, North Dakota Because water varies with where an animal lived, such signals also reveal habitat and possible migration in Triceratops herds.29Palaeogeography, Palaeoclimatology, Palaeoecology. Stable Isotope Record of Triceratops from a Mass Accumulation (Lance Formation, Wyoming, USA) Provides Insights into Triceratops Behaviour and Ecology Enamel is hard and resists change, so these signals survive far better than soft tissue.
Sharing Food With Other Plant-Eaters
Horned dinosaur fossils turn up more often in mudstone, while duck-billed dinosaurs favour sandstone.30PubMed Central. Spatial niche partitioning in dinosaurs from the latest cretaceous (Maastrichtian) of North America Mudstone usually forms in quiet settings and sandstone near active river channels, suggesting Triceratops tended to live farther from rivers and duck-bills closer to them.31PubMed Central. Spatial niche partitioning in dinosaurs from the latest cretaceous (Maastrichtian) of North America Where fossils lie depends on where bodies were buried as well as where animals lived, so this is a pattern across many finds, not a rule for each animal. Competition helped shape which plant-eaters lived together.32PubMed Central. Competition structured a Late Cretaceous megaherbivorous dinosaur assemblage
Different places meant different plants. Vegetation near rivers differs from that on drier, flatter ground, so moving a few kilometres could change the menu more than an animal’s preferences did. Neither group had to fight over the same patch.
The common duck-billed neighbour was Edmontosaurus. It ground food rather than slicing it, another reason the two ate differently.
Tooth chemistry suggests that horned and duck-billed dinosaurs ate different plants.33Paleobiology. Stable isotope evidence for changes in dietary niche partitioning among hadrosaurian and ceratopsian dinosaurs of the Hell Creek Formation, North Dakota But the horned dinosaurs’ own menu moved: at some times they preferred open coastal plants, at others forest understory plants.34Paleobiology. Stable isotope evidence for changes in dietary niche partitioning among hadrosaurian and ceratopsian dinosaurs of the Hell Creek Formation, North Dakota Triceratops adjusted to whatever its surroundings offered.
What Young Triceratops Ate and How Much Adults Needed
Young horned dinosaurs likely ate softer, lower-growing plants than adults.35Carleton University Institutional Repository. Ontogenetic Niche Shifts in Megaherbivorous Dinosaurs of Late Cretaceous North America and their Ecological Implications Young and old therefore competed less for the same food.36Carleton University Institutional Repository. Ontogenetic Niche Shifts in Megaherbivorous Dinosaurs of Late Cretaceous North America and their Ecological Implications A baby had a small skull, growing horns, and a smaller beak and teeth, and small jaws couldn’t slice tough stems. Growing bodies also needed easy-to-digest food, and the diet shifted as the skull and teeth grew. The evidence for exact food choices in youngsters is limited, but the idea fits the changing skull and tooth size.
Adults reached about 9 metres long.37PubMed Central. Wear biomechanics in the slicing dentition of the giant horned dinosaur Triceratops They weighed about 3 to 5 tonnes, similar to an elephant,38Redpath Museum. A triceratopsian diet so they needed far more than a few leaves each day.39Redpath Museum. A triceratopsian diet A Triceratops likely spent much of its day feeding, as an elephant does for many hours. Tough plants give little energy per bite, so volume mattered, and the constant tooth wear followed from this nonstop eating.