In a recent interview on IFLScience's podcast The Big Questions, American paleontologist and science writer Riley Black discussed dinosaur mating behaviors. Despite progress in understanding how dinosaurs lived, what they ate, and the diversity of their species, one question remains largely unanswered: How did these ancient giants reproduce?
"Until we dig up a pair of preserved dinosaurs that were committed to the fossil record mid-mating, we have to get a bit creative when looking for clues about how dinosaurs had sex," Riley Black stated, according to IFLScience. Unlike creatures such as turtles and prehistoric sharks, which have been found fossilized in the act of copulation, no non-avian dinosaur fossils have been discovered in such a state. The lack of preserved soft tissue, particularly reproductive organs that do not fossilize well, adds to the complexity of uncovering their mating habits.
A fossil discovery offers some insight. A Psittacosaurus specimen, described by Riley Black as "sort of a reptilian parrot," has been preserved with soft tissues intact. This fossil exhibits a cloaca—a common cavity used for excretion and reproduction in modern birds, reptiles, amphibians, some fish, and monotremes. "It's almost certain that non-avian dinosaurs had the same kind of anatomy, that any genitals would be held behind that cloaca, and [the Psittacosaurus] is confirmation [of that]," she explained, as reported by IFLScience.
Comparisons with modern animals provide valuable clues. "There's no single modern analog that can act as a good representative for all of Dinosauria, but what we see in birds—and particularly crocodilians—is a good starting point," Black said. Birds, as descendants of theropod dinosaurs, exhibit a range of mating behaviors that might mirror those of their ancient relatives. However, she cautioned that birds' specific traits and behaviors may not be perfect models for all dinosaurs because some evolved after the mass extinction event at the end of the Cretaceous period.
Evidence suggests that at least some dinosaurs engaged in courtship rituals similar to those of modern birds. "We can't yet know if dinosaurs did exactly that, but even when we look to the birds (dinosaurs' other close relatives), we see that courtship displays are widespread," Black noted, as per IFLScience. Trace fossils, such as footprints and ground scratch marks, provide hints about these behaviors. In an area discovered in Colorado in 2016, large carnivorous dinosaurs made scratches on the ground with their feet as part of a courtship display to attract mates, according to Sozcu. This scratching behavior is akin to "prehistoric foreplay" and mirrors movements seen in birds today.
Despite these insights, the physical mechanics of dinosaur mating present challenges, particularly for species with formidable anatomical features. Many dinosaurs, like those of the Stegosaurus species, had large, pointed tails adorned with spikes and plates. "There's probably no non-awkward way for those non-avian dinosaurs to mate," Black admitted, according to IFLScience. The Kentrosaurus, a relative of the Stegosaurus from Tanzania, poses a particular puzzle. "There's a particular stegosaur that I don't understand how these animals managed to reproduce. Its name is Kentrosaurus," she said, noting the difficulty posed by its plates and spikes running from the neck to the tail.
These physical obstacles would have necessitated inventive mating strategies. Weight was another concern. A male dinosaur, sometimes weighing up to 80 tons, would keep mating brief to avoid spending too much time on top of the female, notes Perfil. Zoologist Luis Villazón suggested that very large dinosaurs may have needed the support of water to avoid instability on land during mating, according to Sozcu. This idea reflects the immense size and weight challenges these creatures faced.
Modern reptiles offer further parallels. Black explained that alligators and crocodiles engage in elaborate courtship displays. "Modern alligators and crocodiles have beautiful courtship displays where males lay in the water, rumble, make deep bellowing calls, and cause the water to dance on their backs," she stated, as per IFLScience. Such behaviors hint at the possibility that dinosaurs might have employed similar tactics to attract mates.
This article was written in collaboration with generative AI company Alchemiq