You’ve heard of “never smile at a crocodile”? You may not want to cry around one either.

A new study of Nile crocodiles has found they respond to the sound of human babies crying, as well as infant chimpanzees and bonobos.

Researchers played cries from human, chimpanzee and bonobo infants to a group of Nile crocodiles at a zoo, recording how many of the crocodiles turned their heads or moved toward the speaker. Two contexts were used for human babies: during bath time at home with their parents, which resulted in a low-intensity crying, and vaccination at the doctor’s office, which resulted in higher-intensity crying. The crocs responded most to crying sounds with more energy in higher sound frequencies, as well as crying sounds with some irregularities in the sound patterns; both types could be associated with higher levels of distress.

Is this behavior motivated by trying to find vulnerable prey? Or are they confusing infants’ cries with those of juvenile crocodiles, which can sound like squeaking or cooing? Or are they just curious? The reason isn’t clear.

The interesting part is these crocs may be even better at picking up the level of distress in those cries than we are. In any event, these results give researchers more insight into how these reptilian giants perceive the world.

Taken from “Crocodiles are Drawn to the Wails of Crying Human Babies and Infant Primates” by Ethan Freedman (https://www.livescience.com/animals/alligators-crocodiles/crocodiles-are-drawn-to-the-wails-of-crying-human-babies-and-infant-primates?). The study was published Aug. 8 in the journal Proceedings of the Royal Society B.