A study conducted by scientists from the University of Lyon in France has found that crocodiles have a surprising ability to detect distress in the cries of human and primate infants. These reptiles can recognize distress better than humans can, thanks to their sensitivity to changes in frequency. While most crocodiles may be inclined to attack the source of the crying, some individuals may actually try to protect the infants.
To test the crocodiles’ responses, the researchers played recorded cries of 24 human, bonobo, and chimpanzee infants to groups of Nile crocodiles at a zoo in Morocco. The crocodiles responded by turning their heads, swimming towards the sound, and even biting the speakers. This strong reaction indicates that crocodiles are not typically known for their mobility and that the cries of infant primates prompt them to move.
The crocodiles’ reactions were particularly strong when the recordings had non-linear acoustic characteristics and more intense energy in higher frequencies, which are associated with higher emotional arousal. In contrast, humans tend to assess distress levels based on the pitch of the cry, a characteristic that crocodiles seem to ignore. As a result, humans may misinterpret the distress levels of infants with naturally higher-pitched cries, while crocodiles are less likely to be confused.
It is suggested that crocodiles, which were abundant in the area where human ancestors first evolved, could have posed a significant threat to early human settlements. Although most crocodiles reacted in a predatory manner to the cries, one individual, likely a female, exhibited protective behavior towards the speakers. This behavior is similar to how female crocodiles defend their young from cannibalistic males.
The study’s findings not only shed light on the remarkable ability of crocodiles to detect distress in infant cries but also reveal an ancient danger that early humans may have faced. It is interesting to note that the attractiveness of babies’ cries to crocodiles has long been known and even utilized by European hunters in the past to lure crocodiles into shooting range.
