DENVER, Jan. 7 (UPI) -- Foreplay is as old as the dinosaurs. New fossil evidence shows dinosaurs performed a mating ritual similar to those of modern birds.
Many modern bird species execute "nest scrape displays" or "scrape ceremonies" when attempting to recruit a mate. The precoital routine is supposed to demonstrate a male's abilities as a nest-builder and provider.
Researchers at the University of Colorado Denver say large scrapes fossilized in the prehistoric Dakota sandstone of western Colorado are proof that dinos employed similar rituals. The scraping sites are detailed in a new paper, published this week in the Scientific Reports.
"These are the first sites with evidence of dinosaur mating display rituals ever discovered, and the first physical evidence of courtship behavior," study author Martin Lockley, professor of geology at UC Denver, said in a press release. "These huge scrape displays fill in a missing gap in our understanding of dinosaur behavior."
Lockley and his colleagues found more than 50 scraping sites on federally managed conservation lands near Delta, Colo. Dinosaur tracks had been found in the area previously. Mating evidence was also discovered at nearby Dinosaur Ridge.
Over the course of natural history, the pressures of sexual selection have inspired a variety of unusual performances by both bird and mammal species. But until now, researchers could only speculate as to the mating rituals of dinosaurs.
"The scrape evidence has significant implications," said Lockley. "This is physical evidence of pre-historic foreplay that is very similar to birds today. Modern birds using scrape ceremony courtship usually do so near their final nesting sites. So the fossil scrape evidence offers a tantalizing clue that dinosaurs in 'heat' may have gathered here millions of years ago to breed and then nest nearby."