From the evidence of “mass graves”, fossilized remains of hundreds of individuals found close together, we know that a number of plant-eating dinosaur species must have lived together in herds. Many modern herbivores live like this, too. So palaeontologists’ insight into why some dinosaurs herded together can be helped by studying the behaviour of modern herding animals.

Recognition

Many herding dinosaur species, for example hadrosaurs, had head crests or, in the case of ceratopsians, a neck frill and an array of horns. In both cases, these features probably had several uses. The distinctive shape and colours may have allowed members of the same family group to recognize one another, just as today’s antelopes do from the shape of their horns.

Sexual display

Because the sizes of the crests and horns in fossils vary quite a lot, we can assume that they were larger in males than females—a common feature in many present-day animals. It is therefore likely that males deliberately paraded their crests, horns or neck frills in attempt to win the attentions of females during the mating season. Male peacocks are a spectacular example among the many modern animals that demonstrate this pattern of behaviour, which is known as “sexual display”.

Calls

Parasaurolophus had a long, backwards-curving, bony crest. The hollow tubes inside were linked to its nasal passages. Air blown through the tubes would have made its calls loud and deep—useful for sounding an alarm to its herd, or for warning off rival males.