Many of us may have been moved yesterday when we saw the giant blue moon, but perhaps we will do the same now if we find out that hammerhead sharks also stare at the moon! or not. However, it is certain that female hammerhead sharks gather in large numbers during the summer, during the full moon, on the reefs of Rangiroa and Tikihau in French Polynesia. Life Science.
What is the purpose of these somewhat mystical and feminist meetings? Researchers have put forward several hypotheses, but they do not yet know which one is the real explanation.
A lake in the Tuamotu archipelago hosts the strange encounter, during which researchers counted 54 female hammerhead sharks (in the summer of 2020 and 2021).
More than half of the sharks were non-permanent local residents, staying no more than six days a month, for up to five months.
The great hammerhead is a solitary species, so the large number of females spotted at the same time around the Rangiroa and Tikihau reef rings indicates that they congregate directly here.
The animals may not be related to each other, but external factors may have drawn them here. This can also be the phase of the Moon, because a full moon that shines with great light makes hunting easier and sharks can also react to changes in the Earth’s geomagnetic field (which is associated with the growth of the Moon).
Or, the spontaneous assembly is connected to the eagle ray, which is the sharks’ favorite prey and comes to the lakes to breed.
But it is also possible that the high temperature of the lakes will attract them here. The researchers compared their observations with long-term data collected from the atolls, which revealed that some sharks have returned every summer for 12 years.
The team identified an additional 30 male and female sharks from these records, and found that the males were primarily spotted from August to October, rather than during the summer. Why do the males stay away? Perhaps because the females that emerge in the warm, shallow coastal waters of the lakes congregate here to give birth and raise their offspring.
So either the moon, or the heat, or the stingrays, or perhaps the offspring, are the reasons why the girls have come together for this interesting coastal conference on the coral reefs of French Polynesia.
