Superpods of 600 dolphins are gathering off the coast of South Africa

Bottlenose dolphins are known for hanging out in large pods, but finding more than 50 or 60 in a group is unusual. Now, researchers studying Indo-Pacific bottlenose dolphins (Tursiops aduncus) off the coast of South Africa have found that populations there have skyrocketed, going from an average of just 18 dolphins per group in 2008 to 76 dolphins in 2016. And those are just the averages: Some superpods in Algoa Bay, a shallow inlet off the Eastern Cape, were as big as 600 members, they report this week in Marine Mammal Science . Dolphin pods were larger in the bay (average size 325), than they were offshore (average size 135).

The growth of the pods—and their location—is a mystery. Researchers expected larger groups to be found farther north in the Wild Coast region, where the water is deeper. But instead, the researchers say the dolphins may be gathering in the shallows in large groups for protection against sharks; many white sharks, which have been known to attack dolphins, live in the area.