An initial investigation of the Lunar cycle on the bottlenose dolphins of Montenegrin coastal waters

The lunar cycle’s influence over marine species has recently come under the scope of research. Many studies on organisms at each stage of the trophic levels have been recorded, however, research regarding the lunar cycle’s influence on megafauna within the Adriatic is limited. With a large amount of research investigating the tidal influence on marine life, peer-reviewed research regarding the irradiance of the moon is lacking. We hypothesized that there would be an increase in surface feeding behaviors when plankton and prey have migrated to a more accessible area in the water column with the diel vertical migration, thus attracting tertiary consumers. To investigate the influence of the lunar cycle and the Montenegrin bottlenose dolphin populations, 514 morning surveys were conducted between 2016-2023, with a total of 273 focal groups. Neither surface-feeding behavior nor dolphin presence was found to be associated with the moon phases nor illumination. Spearman’s rank correlation also showed no significant relationship between illumination and surface-feeding percentage. Although no significant relationship was found, surface-feeding behavior was most common during periods of reduced illumination. The findings of this study contradict many studies globally, as the lunar cycle has been seen to influence delphinid species around the world. Perhaps the results could be affected by the oceanic conditions within the Mediterranean, more specifically Montenegro’s neritic waters, due to the shallow bathymetry and low tidal range. Further research looking into the differences between the inside of the bay of Boka Kotorska and the coastal waters would be of interest.