The effect of changes in group composition on social dynamics in marabou storks (Leptoptilos crumeniferus)

The reduction of aggressive behaviors can be a concern whenever animals are socially housed, but for some species, such as marabou storks, zoos are still unsure of the best management strategies. To learn more about marabou behavior and how dynamics change as group composition changes, we monitored a total of 3.5 marabous as individuals were added and removed over 2 years. We found that, in mixed-sex groups, males were more likely to be the initiators of displacements and females were more likely to be the recipients. Most contact aggression was intra-sexual, and females engaged in contact aggression more often than males. The highest levels of aggression were seen in our all-female groups, which was unexpected given the high number of male attacks on females reported in zoos. Because females were being added and removed but our males remained the same throughout the study, we are unsure whether this was due to a higher level of instability among females or a true sex difference; regardless, these data highlight the need to monitor aggression even within all female stork groups. Overall, we observed low levels of inter-sexual aggression, suggesting that some fatal attacks may be due, in part, to non-social factors, such as enclosure design. Social birds like marabous may benefit from the same type of group management approach that is commonly utilized with other social taxa. A two-pronged approach of observation and management of marabou social dynamics and some modification of their enclosure structure may limit injurious aggression in the future.