Long-term cognitive enrichment research provides insight into the change of dolphins' social organisation

We present results from a long-term, seven-year of cognitive enrichment study provided a unique insight into the social organisation of dolphins through cooperation or its absence. Two groups of Indo-Pacific bottlenose dolphins were involved in the study. The first group included five males, one of them replaced with a younger individual. The second group included eight dolphins (six females and two males). One male left the group and joined the first group, the other male joined with another male from the first group. Both groups were tested with three cognitive enrichment devices in four testing steps, before and after the membership changes. The membership change in the first group resulted in a drop in group-level cooperation but led to a higher rate of multi-partner play. These findings may reflect on the changes in the alliances of the male group. In the second, only-female group, interactions with the device increased, and the number of dolphins that were simultaneously involved in these events also increased. Increased activity in the absence of males may reflect on the social organisation of dolphin societies, where males tend to leave, while females stay within the group. The transition of the two young males showed a strong difference. One started cooperating with other males on his first session, while the other, who joined the first group, showed limited participation. These findings provide a valuable insight into the temporal changes of dolphin social organisation and bear further evidence for the value of cognitive enrichments, linking science and welfare.