Scalloped Hammerhead

Fascinating facts about the Scalloped Hammerhead

• Males reach sexual maturity at just 1.5-1.8 m long and about 29 kg, while females need a bigger frame, 2.5 m and roughly 36 kg, before they can reproduce, and the biggest individuals can stretch to 4.3 m and weigh 152 kg. A rare gravid female off Miami measured 3.26 m and tipped the scales at 200 kg, showing that even the "maximum" weight can be exceeded when a shark is full of pups. These size thresholds dictate who can join the breeding pool and shape the species' slow-growing, late-maturing life history.
• Adult scalloped hammerheads leave the open ocean around Cocos Island and travel to the mangrove-lined fjord of Golfo Dulce, where females give birth and pups hide among tangled roots for about three years. After this nursery stint the youngsters head back to Cocos Island to join the pelagic feeding grounds.
• At night the species can form massive schools that sometimes number in the hundreds, a tactic that lets them herd and capture tricky prey more efficiently than solitary hunters. Females dominate these groups, with larger, more mature individuals in the center while smaller sharks stay on the edges, a structure that reduces each shark's chance of being singled out by predators. The sheer size of these aggregations also makes them easy targets for fisheries, linking social behavior directly to conservation risk.
• In the Atlantic, populations have plummeted by more than 95 % over the last three decades, and worldwide an estimated 1.3-2.7 million hammerhead fins are harvested each year for the fin trade. The species was the first shark listed under the U.S. Endangered Species Act and, as of 2019, the IUCN classifies it as Critically Endangered. These stark numbers highlight how overfishing and fin demand have pushed a once-common predator to the brink of extinction.
• Scalloped hammerheads navigate using the Earth's magnetic field, sensed by the Ampullae of Lorenzini on the underside of their "hammer". In the Pacific, they even follow magnetic signatures of cooled magma along ocean-floor fault lines to locate feeding and mating hotspots.

Sources

Every fact above was checked against these pages, and kept only where one of them states it.

• Wikipedia

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