Crocodiles are drawn to the sounds of crying babies, new research suggests.
Nile crocodiles were found to react to the cries of baby bonobos, chimpanzees, and humans — and they appear to be able to detect the degree of distress, research published in Proceedings of the Royal Society B, the Royal Society’s main biological research journal, found.
Researchers played audio recordings of infants crying to the carnivorous crocodiles and discovered they were drawn to those in the most distress.
The researchers explained the reactions as predatory, by giant repitles. However, it could also indicate a maternal instinct among female crocodiles.
Around 300 Nile crocodiles at CrocoParc in Agadir, Morocco, were played the sounds of cries on loudspeakers, per The Independent, with many of the crocodiles responding quickly.
The more distressed the baby, the faster the crocodiles will respond.
“Our experiments obviously do not mean that crocodiles cannot be attracted by other signals than distress calls – they are opportunistic hunters,” the authors wrote in the study, “but they suggest that the readiness of these animals to react increases with the presence of acoustic features marking a level of distress.”
“It cannot be entirely ruled out that some individuals responded in a parental care context,” they said.
The researchers compared the findings to another study in which a group of humans were played the same cries. It revealed that humans and crocodiles use different criteria to judge distress in other species and that humans’ judgment is less accurate.
While crocodiles primarily respond to levels of “deterministic chaotic, harmonicity, or spectral prominents,” humans responded by focusing on the pitch.
The researchers noted that even species far removed from them could identify the level of distress.
Nile crocodiles can grow to about 20 feet long and can weigh up to 1,650 pounds, per National Geographic.
According to the publication, “the creatures live throughout sub-Saharan Africa and Madagascar, in freshwater swamps and rivers.”
According to the publication, Nile crocodiles generally live close to humans, meaning encounters happen relatively often. It estimates that up to 200 people a year die from Nile crocodile attacks.