Researchers in France discovered that the Nile crocodile responds to the distress calls of many different baby animals, including humans.
The predators’ response is sensitive to certain acoustic features, which could help them assess the level of distress in their prey.
Playing recordings of crying bonobosPan paniscus), chimpanzees (Pan troglodytesHumans and other animals are also included. The researchers found that Nile crocodiles prefer to feed on infants who appear in distress.
According to previous studies Crocodiles can be found in many placesThey become alert whenever a potential prey makes distress sounds, and often move towards the sound to try to grab a snack with little effort. Scientists wanted to know if primates and crocodiles were reacted similarly.
The vocalizations from infant primate primates aged 4 or less years were transmitted to Nile Crocodile groups (Crocodylus niloticus(via speakers placed near the pools where more than three hundred of these animals reside in a Moroccan Zoological Park. Behavioral ecologist Julie Thévenet from the University of Saint-Etienne in France and colleagues then studied the crocodiles’ reactions.
C. niloticusisIt is the largest predator of freshwater in Africa. Adult males typically weigh between 225-750 kilograms (500-1650 pounds) but records show they can reach 1,000 kilograms. They also have a frightening length of 6.1 metres (20 feet).
The sounds of primates infants recorded in the past were captured under a variety conditions to show a wide range emotions. Human babies may be in low-distress situations while bathing at home, compared to high-distress situations when receiving vaccinations.
Their cries have been classified according to 18 acoustic parameters and clustered based upon pitch, harmony, and deterministic disorder.
Thévenet and team assessed the crocodiles’ response based on the percentage of individuals in a group that responded to a recording. Thevenet’s team didn’t count the genders of the animals, but they did notice that both males or females turned to the sound when it was played. Some went so far as to bite at the speakers.
The researchers found that the reptiles’ reactions were dependent on the type of cries heard. Only a small percentage of crocodiles reacted to recordings of infants in mild distress.
Results of Study of Human SubjectsThe same stimuli exposed to crocodiles, humans and other animals use different acoustic criterion in assessing the level of distress in infant cries.
Humans often use the pitch to determine how their babies are feeling. Humans often mistakenly interpret high-pitched cries of bonobos as severe distress.
The study found that while pitch is often used to indicate distress, this varies from species to species. It’s also less reliable than other acoustic features like noise bursts and jitter. These are more likely for crocodiles.
These acoustic features are likely to be the cause of a crocodile’s reaction. There are more accurate indicators for distressHuman methods are more efficient. By not paying attention, their responses depend less on the species that is making the sound. This factor doesn’t affect whether or not the sound represents food. Generalist predators.
The team suggests that perhaps crocodiles are able to use this technique so they can target defenseless prey.
”Our experiments obviously do not mean that crocodiles cannot be attracted by other signals than distress calls – they are opportunistic hunters,” the Authors Note“But they suggest that these animals are more likely to react if there is an acoustic feature that indicates a certain level of distress.”
The study has appeared in Proceedings of the Royal Society A: Biological Sciences.
