Carolina Hammerhead

• Maximum lengthNot reliably measured; confirmed specimens are pups and juveniles under 1 m
• WeightNo adult has been weighed
• LifespanUnknown; a preliminary growth model suggests about 21 years
• Depth rangeEstuaries and inner shelf, surface to about 50 m (165 ft)
• DietSmall fish, shrimp, crabs and squid (juveniles); adults unknown
• IUCN statusData Deficient (assessed 2020)

How to recognise a Carolina hammerhead

You cannot, at least not in the water. The Carolina hammerhead is what biologists call a cryptic species: it shares every visible feature of the scalloped hammerhead, Sphyrna lewini. Both have the wide, flattened head with a shallow notch at the centre of the front edge and two smaller notches either side, the scalloped outline that gives the commoner species its name. Both are grey-brown above and white below, with a tall, slightly curved first dorsal fin, a low second dorsal whose free rear tip almost reaches the tail, and an anal fin with a longer base than the second dorsal.

The one character that separates them is inside the animal. A Carolina hammerhead has 83 to 91 precaudal vertebrae, the bones between the head and the tail fin; a scalloped hammerhead has 92 to 99. That gap is what caught the eye of Carter Gilbert of the Florida Museum of Natural History in 1967, when he noted a "scalloped" hammerhead from South Carolina with an oddly low count. Four decades later mitochondrial DNA studies revealed a hidden lineage in the western Atlantic, and in 2013 Joe Quattro and colleagues at the University of South Carolina formally described Sphyrna gilberti, naming it after Gilbert. Genome work in 2023 dated the split between them to 3.8–10.8 million years ago.

A 2023 workshop that measured genetically confirmed pups side by side found no reliable difference in head width, tail-stalk depth or any body proportion. Field identification therefore depends on a tissue sample or an X-ray, and a rapid genetic test that observers could use on deck is the top research priority for the species.

How big does a Carolina hammerhead get?

Nobody knows, and any page that gives you a confident maximum is copying the scalloped hammerhead's figures. Every genetically confirmed Carolina hammerhead measured so far has been a young-of-the-year or a small juvenile from a nursery survey. Six pups examined at the Georgia Aquarium in 2023 measured 39 to 47 cm in stretched total length, and published survey records extend to roughly 70 cm. That is why the maximum length is left blank here rather than filled with a borrowed 3 or 4 m.

What the pups do show is a species that starts life a little smaller than its twin. In shared nurseries, newborn Carolina hammerheads average about 5 cm shorter than newborn scalloped hammerheads, and they gain mass per unit of length more slowly during their first summer. Against that, they are born with a proportionally larger liver, richer in lipid, which suggests that the mother invests more energy in each pup and may therefore carry fewer of them. Whether these differences carry through to smaller adults is an open question.

The reasonable assumption, until an adult is sampled, is that a mature Carolina hammerhead is a large coastal shark of broadly the scalloped hammerhead's build, well over 2 m, with females larger than males.

Where Carolina hammerheads live

Confirmed pups and juveniles come from estuaries and nearshore waters between North Carolina and the Atlantic coast of Florida, with Georgia in between. The heart of the species' distribution appears to be Bulls Bay, a shallow, marsh-fringed bay north of Charleston in South Carolina. It is the only nursery yet found where newborn Carolina hammerheads outnumber newborn scalloped hammerheads, and it is where the type specimens were collected.

Beyond the Carolinas the picture thins out fast. DNA work has picked up the species in a few sharks landed in Brazil, a cryptic lineage first flagged there in 2012, and in Trinidad and Tobago; a single specimen was reported from Campeche on the Gulf coast of Mexico in 2022. It has not otherwise been detected in the Gulf of Mexico or the Caribbean islands, which may simply reflect where the nets have been set.

Habitat, so far as it is known, is the same warm, turbid inshore water used by young scalloped hammerheads: estuaries, sounds and the inner continental shelf to about 50 m. Where adults spend the year is entirely unknown. Satellite tagging cannot begin until researchers can be sure which species they are tagging.

What Carolina hammerheads eat

The only stomachs examined belong to pups, and those tell a plain story. Young-of-the-year Carolina and scalloped hammerheads sharing the South Carolina nurseries eat the same generalist menu of small bony fish, penaeid shrimp, crabs and squid. The two species do not divide the food supply in their first year; they compete for it.

Adults are a different matter, and here the evidence is indirect but interesting. Because a newborn shark's muscle carries the chemical signature of what its mother ate during pregnancy, researchers compared the carbon and nitrogen isotopes of pups from each species. The values differed consistently, which means that mature female Carolina hammerheads either feed in a different food web from mature scalloped hammerheads or take the same prey in different places.

What that adult diet consists of is a guess informed by the relatives. A scalloped hammerhead of 2 to 3 m eats schooling fish such as sardines and mackerel, squid, and bottom-living rays and small sharks, and it uses the wide head to pin stingrays to the sand. The Carolina hammerhead's head is built the same way, with the same forward-facing electroreceptors along its leading edge (see ampullae of Lorenzini), so a similar diet is likely, but nobody has yet opened an adult to check.

Behaviour and adaptations

The hammer, or cephalofoil, is the family's great innovation, and the Carolina hammerhead carries the same model as its twin. Eyes on the tips of the blade give it a field of view that wraps almost fully around the body and, because the eyes are far apart, better depth perception straight ahead than any other shark. The underside of the head is studded with electroreceptive pores, and the flat head acts as a lifting surface that lets the shark turn tighter than a requiem shark of the same size.

Beyond that, the species' behaviour has to be read from its nursery habits. Pups appear in Bulls Bay and the neighbouring sounds each summer, and the timing of the peak is offset from the scalloped hammerhead's peak by some weeks, which suggests the two species give birth on slightly different schedules. Where the pups go after their first autumn is unknown.

One behaviour is documented and worrying: the two species interbreed. A 2019 study found first-generation hybrids between Carolina and scalloped hammerheads in the western North Atlantic, and one of the six pups examined at the 2023 workshop was such a hybrid, with a scalloped vertebral count and several fused vertebrae. For a species that may be far less numerous than its twin, hybridisation is a threat to its identity as well as its numbers.

Reproduction and lifespan

Like every hammerhead, the Carolina hammerhead is viviparous with a yolk-sac placenta: after the embryo has used up its yolk, the empty sac attaches to the uterine wall and the mother feeds it directly for the rest of the pregnancy. Litter size, gestation length and how often a female breeds have never been recorded for this species, because no pregnant female has been identified. In the scalloped hammerhead pregnancy lasts nine to twelve months and litters run from about 12 to 40 pups; the Carolina hammerhead's larger, fatter-livered newborns hint at fewer, better-provisioned pups, but that is a hypothesis awaiting a dissected adult.

Birth takes place in late spring and early summer in the estuaries of South Carolina and neighbouring states, with Bulls Bay the best-documented nursery. Newborns of roughly 40 to 50 cm spend their first summer in the shallows and move out as autumn cools the water.

Age is equally uncertain. A growth curve fitted for a 2021 stock-assessment workshop, from too few samples to be reliable, suggested a maximum age of about 21 years. If the species matures at a similar size to the scalloped hammerhead, at ten years or more for females, then each female may produce only a handful of litters in her life, the slow reproductive arithmetic that makes hammerheads vulnerable (see how long sharks live).

Is the Carolina hammerhead dangerous to people?

No incident has ever been attributed to it, and none could be: since no one can tell a Carolina hammerhead from a scalloped hammerhead without a laboratory, every hammerhead bite ever logged has been recorded as "hammerhead" or as one of the three big species. The SharkSider database holds 51 records attributed to hammerheads of any kind, three of them fatal, the last death in 1981; of the 13 records since 2000, most involve anglers, kayak fishers and spearfishers handling hooked or speared sharks, and none was fatal. Some of the Carolina records may in principle involve this species; there is no way to know.

What can be said is that the animals people actually meet, the pups and juveniles in the sounds of the South Carolina and North Carolina coasts, are under a metre long and harmless. Hammerheads as a family are shy of swimmers and the few serious incidents involve large adults provoked by fishing gear. Treat a hooked hammerhead of any species with respect and cut the line rather than dragging it up the beach, for its sake more than yours (the practical advice is on how to survive a shark encounter).

The SharkSider database has no incident attributed to this species. The database draws on the International Shark Attack File, the Global Shark Attack File and verified local reports, and is updated weekly.

Conservation status

The IUCN Red List assessed the Carolina hammerhead as Data Deficient in 2020: too little is known about its range, abundance and life history to place it in a threat category. Its twin, the scalloped hammerhead, is Critically Endangered, and every threat that drives that listing applies to a shark that is caught in the same nets on the same coast and cannot be sorted from it at the dock. Since November 2023 it has been covered by CITES Appendix II along with every other hammerhead, after the whole family Sphyrnidae was listed at CoP19 in 2022; scalloped hammerheads had been on Appendix II since 2014, and any Carolina hammerhead fin in trade falls under the same paperwork.

The main pressure is fishing. Scalloped hammerheads die on bottom longlines at a rate of about 63 per cent before the gear is even hauled, and roughly 69 per cent of those released alive die afterwards; the workshop that reviewed the Carolina hammerhead assumed the same figures. Pups and small juveniles are taken in gillnets and shrimp trawls, and outside US waters, in Trinidad and Brazil, artisanal fisheries land small hammerheads without distinguishing species. Coastal nurseries such as Bulls Bay are exposed to development and to warming, and hybridisation with the far more numerous scalloped hammerhead is a further, unusual risk.

In the United States the species is managed by default inside the hammerhead complex of the Atlantic shark fishery. Most Atlantic states ban gillnets in state waters, which gives the nurseries some refuge, and Florida has prohibited the landing of scalloped, great and smooth hammerheads from its waters since 2012, a rule that protects Carolina hammerheads in practice. A stock assessment specific to the species has so far been impossible for want of data (see why sharks are endangered).

Similar species and close relatives

The scalloped hammerhead is not merely similar; it is indistinguishable in the field, and the two share nurseries along the south-eastern United States. The great hammerhead is larger, with a nearly straight front edge to the head, a very tall sickle-shaped first dorsal fin and serrated teeth; the smooth hammerhead has a rounded head without the central notch and lives in cooler water. All three big species overlap with the Carolina hammerhead off the Carolinas and Florida.

The smaller members of the family are easier to separate. The bonnethead of the same estuaries has a spade-shaped head and rarely passes 1.2 m; the scoophead and smalleye hammerhead of the Caribbean and Brazil are small sharks with distinctive head shapes, and the smalleye is golden in colour. A general introduction to the family is on our hammerhead shark page. If you catch a scalloped-looking hammerhead in the sounds of South Carolina, the honest answer to "which species is it?" is a shrug, unless a biologist takes a fin clip.

• Scalloped Hammerhead Sharkspecies profile
• Great Hammerhead Sharkspecies profile
• Smooth Hammerheadspecies profile
• Bonnethead Sharkspecies profile
• Scoophead Sharkspecies profile
• Smalleye Hammerheadspecies profile

Written and reviewed by

SharkSider Editorial Team

A small team focused on researching sharks and making marine biology easy to understand. Every page is reviewed against current species records and the SharkSider attack database, and updated when new incidents or research appear.

Published August 24, 2022 · Last updated September 22, 2026 · No incident attributed to this species in the SharkSider attack database, which is updated weekly.