Agonistic behavior and feeding competition in the largest piranha species, Pygocentrus piraya, in a zoo

Publication Type:
Journal Article
Year of Publication:
Ronald G Oldfield, Josie E Thal, Praanjal Das, Nick J Zarlinga, Kristen E Lukas, Jason D Wark
Journal of Ethology
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In the wild, piranhas are thought to feed in groups. Previous studies on piranhas in aquariums have variously observed either social attraction or aggressive dominance. The Rio São Francisco piranha (Pygocentrus piraya) is the largest species of piranha. It is rare in aquarium collections and its social and feeding behaviors have never been studied. To better understand behavior in this species, we observed a group of individuals housed in a zoo. We did not observe social attraction or grouping behavior. Individuals generally remained inactive except during aggressive interactions, or to consume food when available. They were organized in a weakly linear dominance hierachy. Dominant individuals performed more aggressive bouts and fewer retreats than subordinate individuals. We also found differences among individuals in the number of pieces consumed and in contesting other individuals for food. Social behavior in animals is known to vary plastically according to available space and number of competitors, and these factors might have influenced behavior in the current study. This study highlights the value of zoos for studying species that would otherwise be inaccessible, and it provides fundamental information that can later be used to enhance welfare of piranhas in aquariums.


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