Scalloped hammerhead

Off Hawaiʻi, scalloped hammerheads dive deeper than 1,000 m and hold their breath to keep warm.

At a Gulf of California seamount, tracked sharks swam on very straight paths, perhaps following the Earth's magnetic field.

It is a different species from the great hammerhead.

Off Hawaiʻi, scalloped hammerheads hunt as deep as 1,044 m, where the water is about 5°C. There they close their gill slits, holding in body heat like a held breath.

Source: University of Hawaiʻi News, 2023, on Royer et al., Science: hammerheads hold their breath to stay warm

At a seamount in the Gulf of California, tracked scalloped hammerheads swam out and back on very straight paths. Scientists think they may follow the Earth's magnetic field.

Source: Klimley, 1993, Marine Biology, Highly directional swimming by scalloped hammerhead sharks

Of 84 scalloped hammerheads tagged at Cocos Island over nine years, only one was later found at another island in the region. Sharks from the Galápagos and Malpelo visited Cocos more often.

Source: Nalesso et al., 2019, PLOS ONE, island connectivity of scalloped hammerheads

At Darwin and Wolf in the Galápagos, surveys in 2013 and 2014 found 17.5 tonnes of fish per hectare, the largest reef fish biomass reported. Scalloped hammerheads made up 48% of it. Ecuador made the area a no-take sanctuary in March 2016.

Source: Salinas-de-León et al., 2016, PeerJ, Largest global shark biomass found in the northern Galápagos

At Madivaru off Rasdhoo Atoll, Maldives, divers once saw dozens or even hundreds of scalloped hammerheads early in the morning. Over the last decade, sightings have become rare.

Source: IUCN SSC Shark Specialist Group, Eastern Rasdhoo Atoll ISRA factsheet, 2023

Off Cape Irizaki on Yonaguni, Japan, groups of up to 200 scalloped hammerheads gather from December to March. Most are large females, and some look pregnant.

Source: IUCN SSC Shark Specialist Group, Yonaguni Island ISRA factsheet, 2024