Dinosaur courtship: traces, display and uncertainty

Courtship leaves few unambiguous fossils. A skeleton can preserve a crest, horn or unusually shaped bone, but not the social signal an animal produced with it. A footprint records a step, not its purpose. Even a striking cluster of traces can admit more than one explanation. The best-supported account of dinosaur display therefore begins with what is physically preserved and treats mating behaviour as an interpretation.

Scrape marks that may record display

At several Cretaceous sites in Colorado, researchers described broad scrape marks made by the feet of large theropods. The traces consist of paired grooves and displaced sediment on ancient surfaces. Some show repeated scratching in one place. Their authors proposed that the animals created display arenas, drawing a cautious comparison with ground-scraping displays by living birds.

The trace maker was not preserved beside every mark, so assigning a precise dinosaur species is difficult. A theropod attribution is based on the size, shape and movement implied by the traces and the geological context. The proposed “lek” interpretation is plausible, but not uniquely demonstrated: digging, nest preparation or another repeated activity could produce some scraping patterns. The site records contact between feet and sediment. It does not record an audience, mating, vocalisation or a successful courtship.

Living birds are useful comparisons because they are the only surviving dinosaur lineage, and crocodilians offer another living archosaur perspective. But modern behaviour is an analogy, not a time machine. Similar structures can serve different functions in different species. The history of early birds shows how many display-related features evolved within the avian branch; it does not establish the behaviour of every non-avian theropod.

What body structures can and cannot tell us

Head crests, horns, frills and elaborate feathers may have helped animals recognise, signal or compete with one another. Their distribution can support a display function when a structure varies greatly between close relatives or develops as an animal matures. If a structure changes little across species and appears mechanically useful, other functions may be more likely. Multiple functions are also possible.

Bone texture, growth series and rare skin or feather impressions help test these ideas. A hollow crest may have altered sound resonance, but an air passage does not by itself prove a particular call. A tall ornament may have been visible at a distance, yet visibility alone cannot distinguish courtship from species recognition or threat. Colour is especially uncertain unless preserved pigment structures or chemical residues provide direct clues.

Some dinosaurs have been found with vivid preserved feather patterns, and the fossil record shows that feathers served functions beyond flight. Those data demonstrate that visual display was biologically available. They do not tell us the exact seasonal ritual, partner choice or social rules of an animal from a single impression.

Tracks and groups are ambiguous evidence

Trackways can show that animals walked or ran across a surface, how their feet contacted the ground and whether several individuals passed nearby. Parallel tracks may indicate animals moving in the same direction around the same time. They do not necessarily show that the animals travelled as a family, formed a mating group or repeated the route each year.

Likewise, a bonebed with many animals can arise from a drought, flood, trap, transport or accumulation over a long period. It should not be treated as proof of a herd or courtship gathering without sedimentological and age-distribution evidence. The distinction between an association at death and a living social group is central to reconstructing dinosaur behaviour.

How strong behavioural claims are tested

Researchers compare several independent observations: the geometry of the trace, its position in the sediment, repeated patterns, known foot anatomy, associated tracks and the way the site formed. For body structures, they compare close relatives, growth stages, internal anatomy and mechanical demands. A hypothesis becomes stronger when one explanation accounts for several features and alternatives fit less well.

Even then, fossils rarely preserve the full event. A mark might be made during courtship, territorial display or nest preparation; each claim carries a different level of confidence. The most responsible wording reflects that ladder of evidence. “Consistent with a display scrape” is more accurate than “dinosaurs performed a mating dance here.”

A cautious picture of courtship

Dinosaurs almost certainly communicated and competed, as living animals do, and their varied anatomy supplied possible visual, acoustic and tactile signals. Fossils give particularly suggestive clues from ornaments and the Colorado scrape traces. They cannot reconstruct a universal dinosaur courtship season or prove elaborate pair-bonding systems.

The best answer is therefore specific and provisional: some trace surfaces may preserve repeated display-like scraping, while crests and feathers could have contributed to signalling. The exact behaviour remains unknown. Further discoveries with tracks, sediment context and associated remains may narrow the possibilities, but interpretation must keep the evidence visible alongside the story.