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http://www.chester.ac.uk/origin/2001/2.pdf

An investigation of behavioural interaction
within a group of freshwater stingrays
Potamotrygon motoro
Sara Wren
Module: Dissertation ¥ Supervising Tutor: Dr Alison Fletcher
Abstract
The courtship and mating behaviour of stingrays is complex with few direct observations
documented either in the wild or in captivity. It is known that during the mating
season male stingrays bite a femaleÕs disc during copulation leaving visible marks, but
other visible wounds may be present due to non-copulatory biting or aggression. This
study investigated the behavioural interaction of a group of freshwater stingrays,
Potamotrygon motoro, consisting of two females (FA and FB) and one male (MC) at
Chester Zoo. Female B and MC had both sustained bite marks to the posterior area of
their discs and the study aimed to suggest reasons for these bites through investigation
of group dynamics. Focal subject sampling was used to observe the behaviour patterns,
proximity and approach and departure of the stingrays. There was a signiÞcant
difference in MCÕs relationship with FA and FB. Male C glided over, approached and
rested in contact more often with FB than he did with FA. Investigation of the relationship
between the two females showed that FA glided over and approached FB
more often than FB glided over and approached FA. Whilst there was no evidence of
a clear dominance hierarchy within the group, it was observed that FA completely
covered FB (ÔtoppingÕ) when they rested in contact which might be interpreted as
dominant behaviour on the part of FA. It is suggested that FBÕs wounds may have
been caused by courtship bites inßicted by MC or perhaps as a result of aggression
from FA. It is unclear how MC received his wounds, but it would seem unlikely that it
was due to FB due to her passive part in their relationship. To fully understand behavioural
interaction in captive stingrays, further research is required.