Sound production and behavior in red-bellied piranhas

Psychology

Animal Behaviour

The hypothesis of the article "Sound production in red-bellied piranhas (Pygocentrus nattereri, Kner): an acoustical, behavioural and morphofunctional study" by Millot, Vandewalle & Parmentier (2011), is that piranhas make sounds and these sounds are able to be associated with given behaviors like aggression, intimidation, food competition, and chasing and that these sounds were generated by rapid contractions of sonic muscles that insert on a broad tendon surrounding ventrally the cranial sac of the swimbladder.

One strength of the Experimental Design

A strength of the experimental design was that the researchers made direct underwater observations of the feeding and social interactions of red-bellied piranhas. They examined breeding behaviour, described how individual piranhas attacked goldfish and investigated piranha shoaling behaviour in a controlled environment.

One Weakness of the Experimental Design

A weakness of this experimental design was that there was no testing of the vibratory capacities of the cranial and caudal sacs to see if this might have been the source of the sounds being recorded. To date the exact role of both sacs in sound production remains poorly understood and really could use some further research in order to see what role, if any they play in the sound production of piranhas.

Follow up Study to Test the Same Hypothesis

A follow up study that could be done in order to test the same hypothesis would be to test the same type of fish in their natural environment instead of in a tank environment. The same variables of the cranial and caudal sacs would be observed in order to determine if the sounds being produced where indeed coming from these organs or not. It may be that these two organs are either the source of the sound or are in someway related to the sound that these researchers heard during the tank experiment coming from the swimbladder.

Did the newspaper article describe the research article correctly? Explain.

The newspaper article "Hearing the Repertoire of a Very Fearsome Fish" by Bhanoo (2011) did a good job in describing the research article correctly. It described how the researchers used piranhas to study and how they used a hydrophone to record underwater sounds coming from the piranhas. It described how the sounds made were recorded during fighting, charging and frontal display. The author explained how it was previously believed that piranhas produced only a single barking sound, but the these researchers also recorded a drumlike sound, made when the fish fought for food, and a croak the fish's jaws produced when it snapped at another piranha. The article also discussed the fact that the researchers discovered that piranhas make the barking and drumming sounds by rapidly contracting a muscle that is attached to the swim bladder.