It was long unclear how Oviraptor, a bird-like but flightless dinosaur, hatched its eggs. Did they rely on heat from their surroundings, like crocodiles, or did they directly incubate their eggs, like birds? new research in Frontiers of ecology and evolution explore this question by examining the nesting behavior and hatching patterns of Oviraptors.
Researchers in Taiwan combined heat transfer simulations with physical experiments to better understand how these dinosaurs hatched their eggs. They also compared their discovery to the hatching of modern birds. To do this, they built a life-size model of an oviraptor and a realistic nest to test how heat moves through the eggs.
“We showed that differences in oviraptor hatching patterns were caused by the relative positions of the adults and eggs during hatching,” said lead author Dr. Tzu-Ruei Yang, associate curator of vertebrate paleontology at the National Museum of Natural Science, Taiwan.
“We also obtained an estimate of the hatching efficiency of Oviraptor, which is much lower than that of modern birds,” added lead author Chun Yu-Su, who was attending Washington High School in Taichung at the time the study was conducted.
Rebuild the oviraptor nest
The model was based on Huangyuanniaa type of oviraptor that lived in what is now China between 70 and 66 million years ago. This dinosaur was about 1.5 meters long and weighed about 20 kilograms. Builds a semi-open nest in which multiple eggs are placed in a ring.
To recreate this animal, researchers constructed a torso using expanded polystyrene and a wooden frame and added cotton, bubble paper, and fabric to mimic soft tissue. The eggs were made from cast resin. In the experiment, two clutches were placed in a double ring, consistent with fossil evidence.
“Part of the difficulty lies in realistically reconstructing oviraptor hatching,” Hsu said. “For example, oviraptor eggs are different from eggs of modern species, so we invented resin eggs to get as close as possible to real oviraptor eggs.”
Heat, nest design, hatching pattern
The research team tested how both the presence of adults and environmental conditions affected egg temperature and hatching outcomes.
In colder conditions, the temperature of the egg outer ring varied by up to 6°C in the presence of a brooding adult. Such differences can lead to asynchronous hatching, where eggs within the same nest hatch at different times. In warmer environments, the variation decreased to about 0.6°C. This suggests that in warmer climates, sunlight may have helped equalize temperatures and influenced hatching patterns.
“It is unlikely that large dinosaurs were sitting on clutches. Like turtles, they would have used heat from the sun or the soil to incubate their eggs. Oviraptor’s clutches are open to the air, so heat from the sun was likely much more important than heat from the soil,” Yang explained.
Dinosaur and bird hatching efficiency
The researchers also compared Oviraptor’s hatching to that of modern birds. Most birds rely on thermoregulatory contact incubation (TCI), where the adult sits directly on the egg and provides heat. For TCI to work, the adults must touch all the eggs and act as the main heat source, keeping the temperature constant.
Oviraptor probably could not meet these conditions. The ring-shaped arrangement of eggs prevents adults from maintaining contact with all eggs at once.
“Oviraptor may not have been able to perform TCI like modern birds,” Hsu said. Rather, it’s more likely that these dinosaurs and the heat of the environment worked together to become co-incubators. Although this method was less efficient than that of modern birds, it may have been well suited to their nesting style, which appears to have transitioned from buried to semi-open nests.
“Modern birds are not ‘good’ at incubating their eggs. On the contrary, modern birds and oviraptors have very different methods of incubation, and more specifically, incubation,” Yang pointed out. “There’s no good or bad. It depends on the environment.”
What does this mean for dinosaur parenting?
The researchers cautioned that their results are based on reconstructed nests and modern environmental conditions, which are different from those from the Late Cretaceous. These differences may influence the findings. They also note that Oviraptor likely had a longer incubation period than modern birds.
Despite these limitations, the study provides new insight into how oviraptors cared for their eggs. By combining physical models and simulations, this study opens new possibilities for dinosaur reproduction research.
“This is really encouraging for all students, especially in Taiwan,” Yang concluded. “There are no dinosaur fossils in Taiwan, but that doesn’t mean we can’t study dinosaurs.”
