Pre-copulatory bite wounds as evidence of aggressive competition for mating in the neotropical freshwater stingray Potamotrygon motoro

Reproductive aspects of Amazonian freshwater stingrays are still poorly studied, however, it is known that the copulatory behavior in some species is related to the hydrometric seasons (high and low water). In order to assess the reproductive activity prior to copulation, we examined bite wounds in Potamotrygon motoro of Catalao Lake, in Amazonas state, Brazil. Specimens of both sexes showed wounds on the pectoral fins. Males presented a large amount of bite wounds, distributed randomly throughout the body, while females had more bite wounds on the posterior region. The higher number of wounds in males is assumed to indicate aggressive interactions among males in competition for females, caused by attempts to prevent other males from mating with the target female. The behavior is likely owed to the confinement of the stingrays in the lake during the low-water period.

Automated summary

In this study, we examined bite wounds in Potamotrygon motoro of Catalao Lake in the Amazonas state of Brazil to assess reproductive activity prior to copulation. Both male and female individuals showed wounds on their pectoral fins. Males had a higher number of bite wounds distributed randomly throughout the body, while females had more bite wounds on the posterior region. This suggests aggressive interactions among males in competition for females.