As many as 400 megalodon teeth were found at the sites, giving rise to this theory. The size of most of the teeth, about 0.6 to 2.8 inches, suggests that the majority had come from juveniles and embryonic sharks.

Juvenile teeth are different from the small teeth from adults or the dwarf species of the megalodon. In all, it is estimated that the teeth came from 21 juvenile megalodons and seven adults, possibly the mother sharks.

"It is amazing how we were able to reconstruct a behavioural strategy used by ancient sharks based on fossils," said researcher Catalina Pimiento, a biologist at the University of Florida and the Smithsonian Tropical Research Institute.

This is the first decisive evidence that the megalodon had nurseries.