Researchers from the University of Saint-Etienne and University Lyon in France have shown that Nile crocodiles respond to a variety of young mammal screams, including human cries. In their study, reported in the journal Proceedings of the Royal Society B: Biological Sciences, the group tested crocodile reactions to recordings of babies crying at CrocoParc in Agadir, Morocco.
According to earlier studies, when crocodiles hear their prey in distress, they often perk up and move toward the sound in pursuit of a quick and simple meal. The research team questioned whether crocodiles would react similarly to other species that are not necessarily prey in this new study.
They gathered a number of recordings of infants from various species crying or shrieking in distress in order to find out. These infant sounds, made by chimpanzee, bonobo, and human neonates under varied levels of stress, were captured on tape. Human recordings included wailing babies receiving immunizations at a pediatric clinic and at home.
The researchers next traveled to CrocoParc, an outdoor facility built to host more than 300 crocodiles, in Morocco. The crocs in the park are free to explore the grounds and act nearly as though they were wild animals. The researchers placed up speakers there and played the recordings while capturing the crocodiles’ responses.
The team found that most of the crocs responded to the recordings. They also observed that when hearing cries that were incredibly stressed out, replies tended to be more urgent. Additionally, they discovered that most people responded quickly, particularly when the sounds suggested that an infant of some kind might be in danger.
Notably, after approaching the speaker from which baby screams were coming, one crocodile, probably a female, abruptly turned around and confronted the other crocodiles who had replied. According to the researchers, such a reaction was comparable to how a mother would react to defend her children.
The study team comes to the conclusion that newborn cries are universal and that infants who stray too far from parental protection have a lengthy history of being eaten by crocodiles.
