We’re not entirely sure. Studying marine mammals at sea is tricky at the best of times, let alone during bad weather.
It has been suggested that coastal dolphins can sense changes in atmospheric pressure, heading for deeper, less turbulent waters before the bad weather hits. Cetaceans exhale explosively and then inhale again very quickly, requiring them to spend relatively little time at the surface.
Nevertheless, heading for the deep is probably wise, as very strong storms can have devastating effects – one bottlenose population in the Gulf of Mexico decreased by a third after Hurricane Katrina in 2005.
We’re only just beginning to understand how these mammals recuperate in the aftermath of such weather events. One study showed that dolphins can restructure their social groups, replacing lost members with new ones entering the community. Another noted decreased levels of aggression between bottlenose and Atlantic spotted dolphins, the males of which fight to establish dominance. Long-term implications are still unknown.