---
title: "What the sources say about the Great Hammerhead Shark | AnimalTracks.wiki"
description: "64 claims from the Great Hammerhead Shark profile, each beside the words of the source that backs it."
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# What the sources say about the Great Hammerhead Shark (*Sphyrna mokarran*)

> 64 claims from the Great Hammerhead Shark profile, each beside the words of the source that backs it. A "..." marks a cut in a quote and [brackets] an insertion.

Profile: [Great Hammerhead Shark](https://animaltracks.wiki/animals/great-hammerhead/)

## Sphyrna mokarran. Florida Museum of Natural History, Discover Fishes.

https://www.floridamuseum.ufl.edu/discover-fish/species-profiles/sphyrna-mokarran/

| The page says | The source says |
| :--- | :--- |
| wired with electric sensors | hammerheads have small pores or “ampullae of Lorenzini”, distributed along the ventral surface of their head. The pores are gel-filled and serve as highly sensitive electrical receptors |
| Warm temperate and tropical coastal waters, coral reefs, and continental shelves worldwide | found in coastal warm temperate and tropical waters within 40°N – 35°S latitude ... commonly in shallow coastal areas such as over continental shelves and lagoons |
| Stingrays and other rays | known to prefer stingrays and other batoids when available (Compagno et al., 2005) |
| bony fish | eats bony fishes and invertebrates, as well as other sharks and rays (Denham et al., 2007) |
| other sharks | eats bony fishes and invertebrates, as well as other sharks and rays (Denham et al., 2007) |
| Ampullae of Lorenzini, gel-filled pores under its head that sense the electrical signals of prey, even prey buried in sand | hammerheads have small pores or “ampullae of Lorenzini”, distributed along the ventral surface of their head. The pores are gel-filled and serve as highly sensitive electrical receptors that are used, among other things, to detect the electrical signals that are emitted by potential prey items – including those that are buried under the sand such as stingrays |
| The Largest of the Hammerheads | The great hammerhead is the largest of the hammerheads in the family Sphyrnidae |
| is the largest of the hammerhead sharks | The great hammerhead is the largest of the hammerheads in the family Sphyrnidae |
| It can reach a maximum length of 18 to 20 feet | They can reach a maximum length of 18-20 feet (Compagno et al., 2005) |
| averages over 500 pounds (230 kg) | the great hammerhead averages over 500 pounds (230 kg) (note: The current Florida Museum page overrides ADW's older, heavier 350 to 500 kg range, which the page does not use) |
| One caught off Sarasota, Florida, weighed 991 pounds (450 kg) | The world record great hammerhead was caught off Sarasota, Florida (US) weighing 991 pounds (450 kg) (note: The page states the individual's weight, not that it is still the world record: a current record needs a source dated after the latest catch, and the page is undated) |
| Great hammerheads are expected to live 20 to 30 years | Expected life span of the species is 20-30 years of age |
| from the Gulf of Mexico and the Caribbean to the Mediterranean, the Indo-Pacific and the Pacific coasts of Mexico and Peru | it ranges from North Carolina (US) south to Uruguay, including the Gulf of Mexico and Caribbean regions ... from Morocco to Senegal, including the Mediterranean Sea ... from the Ryukyu Islands to New Caledonia and French Polynesia. In the eastern Pacific it ranges from southern Baja, California (US) through Mexico, south to Peru |
| It is often found in shallow water down to 80 meters, over continental shelves (the shallow seabed that borders the land) and in lagoons, but it also ranges far offshore as deep as 300 meters | This large coastal/semi-oceanic shark is found far offshore to depths of 300m (Myers, 1999), but are commonly in shallow coastal areas such as over continental shelves and lagoons to depths of 80 m (note: The parenthesis defines 'continental shelf' in plain words; it states nothing about the shark) |
| Some populations move toward cooler water each summer | The great hammerhead migrates seasonally, with some populations moving poleward to cooler waters during the summer months |
| Sensing Buried Prey | detect the electrical signals that are emitted by potential prey items – including those that are buried under the sand such as stingrays |
| Its hammer-shaped head is called a cephalofoil | Anterior margin of cephalofoil straight and hammer-shaped |
| Like all sharks and rays, it has small gel-filled pores called ampullae of Lorenzini along the underside of its head | As with all sharks and rays, hammerheads have small pores or “ampullae of Lorenzini”, distributed along the ventral surface of their head. The pores are gel-filled |
| They work as highly sensitive electrical sensors, picking up the signals given off by prey, even a stingray buried under sand | serve as highly sensitive electrical receptors that are used, among other things, to detect the electrical signals that are emitted by potential prey items – including those that are buried under the sand such as stingrays |
| Great hammerheads are known to prefer stingrays and other rays when they can find them | They are known to prefer stingrays and other batoids when available (Compagno et al., 2005) (note: Batoids are the rays; 'when they can find them' is the source's 'when available') |
| Great hammerheads also eat bony fish, squid and other sharks | eats bony fishes and invertebrates, as well as other sharks and rays (Denham et al., 2007) (note: Squid is ADW's (claim 'squid': 'invertebrates such as squid and octopus')) |
| The underside of its hammer-shaped head is dotted with ampullae of Lorenzini, small gel-filled pores that act as highly sensitive electrical receptors | hammerheads have small pores or “ampullae of Lorenzini”, distributed along the ventral surface of their head. The pores are gel-filled and serve as highly sensitive electrical receptors |
| All sharks and rays have them | As with all sharks and rays, hammerheads have small pores or “ampullae of Lorenzini” |
| They pick up the electrical signals given off by prey, including stingrays buried under the sand | used, among other things, to detect the electrical signals that are emitted by potential prey items – including those that are buried under the sand such as stingrays |
| The Florida Museum counts 17 unprovoked attacks on people by hammerheads of all species, none fatal | According to the International Shark Attack File, there have been 17 unprovoked attacks with no fatalities for all species of the genus Sphyrna (note: body; the sentence stats.dangerLevel: High rests on. The page is undated, so the count is attributed to the museum rather than stated as current (#218)) |
| says few can be pinned on this one because hammerheads are hard to tell apart | However, few of the attacks can be directly attributed to this species as it is generally difficult to distinguish among species of hammerheads involved in attacks (note: body; stats.dangerLevel) |

## Sphyrna mokarran (great hammerhead). Animal Diversity Web, University of Michigan.

https://animaldiversity.org/accounts/Sphyrna_mokarran/

| The page says | The source says |
| :--- | :--- |
| coral reefs | These sharks inhabit both the pelagic and coastal regions in coral reefs, inland seas, lagoons, and bays in tropical and subtropical environments |
| squid | invertebrates such as squid and octopus (note: Florida Museum says only 'invertebrates'; ADW names squid. No disagreement between the two) |

## Piercy, Carlson & Passerotti (2010). Age and growth of the great hammerhead shark, Sphyrna mokarran, in the north-western Atlantic Ocean and Gulf of Mexico. Marine and Freshwater Research.

https://doi.org/10.1071/mf09227

| The page says | The source says |
| :--- | :--- |
| A 2010 study aged 216 sharks from the Gulf of Mexico and the northwest Atlantic by counting yearly growth bands in their backbones, and the oldest was 44 | age and growth estimates for the great hammerhead were determined from sharks (n = 216) ranging in size from 54- to 315-cm fork length (FL), captured in the Gulf of Mexico and north-western Atlantic Ocean ... Annual band pair deposition was confirmed ... Great hammerheads have one of the oldest reported ages for any elasmobranch (44 years) ... The present study is the first to provide vertebral ages for great hammerheads (note: Vertebral ages = growth bands counted in the backbone. The 2010 comparison 'one of the oldest reported ages for any elasmobranch' was cut: it is a record dated 2010, and later shark ages exceed it) |

## Rigby et al. (2019). Sphyrna mokarran. The IUCN Red List of Threatened Species 2019: e.T39386A2920499.

https://doi.org/10.2305/iucn.uk.2019-3.rlts.t39386a2920499.en

| The page says | The source says |
| :--- | :--- |
| Critically Endangered | IUCN Red List category: Critically Endangered (CR) |
| The great hammerhead is listed as Critically Endangered on the IUCN Red List | IUCN Red List category: Critically Endangered (CR) (note: Read through GBIF's current copy of the Red List) |

## Payne et al. (2016). Great hammerhead sharks swim on their side to reduce transport costs. Nature Communications.

https://doi.org/10.1038/ncomms12289

| The page says | The source says |
| :--- | :--- |
| Swimming on Its Side | Great hammerhead sharks swim on their side to reduce transport costs |
| It Swims on Its Side to Save Energy | Great hammerhead sharks swim on their side to reduce transport costs |
| A wild great hammerhead tagged on the Great Barrier Reef spent about 90% of an 18-hour tracking period | the shark tagged at the Great Barrier Reef spent ∼90% of the 18 h deployment period (which was from early evening till late morning) swimming on its side at absolute roll angles between 50° and 75° (note: Matches the body and FAQ 3. Two sharks were tagged; the abstract's 'up to 90%' is this one shark's figure) |
| tilted 50 to 75 degrees onto one side | swimming on its side at absolute roll angles between 50° and 75° |
| rolled 50 to 75 degrees onto one side | swimming on its side at absolute roll angles between 50° and 75° |
| Almost all sharks get lift, the upward push that stops them sinking, from the pectoral fins on their sides | Almost all sharks are negatively buoyant ... and use their pectoral fins to generate vertical hydrodynamic force that counteracts gravity |
| A great hammerhead's dorsal fin, on its back, is longer than those side fins, the opposite of every other shark measured | the dorsal fin of a great hammerhead is longer than its pectoral fins; the opposite is true for all other sharks for which we have data |
| Tilting lets the dorsal fin share the work of making lift | Rolling on its side, a shark gradually transfers some of the lift from its pectoral fins to the dorsal fin (note: Replaces 'instead of their pectoral fins': Fig. 2 has lift from 'the combination of the pectoral and dorsal fins at greater roll angles') |
| Its dorsal fin is longer than its pectoral fins, so tilting lets the dorsal fin help make lift | the dorsal fin of a great hammerhead is longer than its pectoral fins ... Rolling to its side, a great hammerhead therefore increases the horizontal span of its lift-generating surfaces |
| In wind tunnel tests on a model shark, tilting cut drag, the force that slows a swimmer down, by more than 10% | we built a morphologically accurate model of a great hammerhead ... and conducted a series of experiments in a wind tunnel ... At the relevant range of lift coefficients, the reduction in drag is more than 10% |
| In wind tunnel tests on a model shark, tilting cut drag by more than 10% | we built a morphologically accurate model of a great hammerhead ... and conducted a series of experiments in a wind tunnel ... At the relevant range of lift coefficients, the reduction in drag is more than 10% |
| The researchers estimate it uses about 8% less energy to cover the same distance | the COT estimates are shown in Fig. 3c,d ... ∼8% less energy is used to travel a given distance when swimming rolled than when swimming upright |
| To save energy | Great hammerhead sharks swim on their side to reduce transport costs |
| swims tilted 50 to 75 degrees onto its side | swimming on its side at absolute roll angles between 50° and 75° (note: vibe.reason; replaces 'panoramic ocean resonance', a place word (#218)) |
| a roll estimated to save about 8% of the energy of swimming upright | ∼8% less energy is used to travel a given distance when swimming rolled than when swimming upright (note: vibe.reason; the 8% is the researchers' estimate from the model, hence 'estimated') |

## Roemer, Gallagher & Hammerschlag (2016). Shallow water tidal flat use and associated specialized foraging behavior of the great hammerhead shark (Sphyrna mokarran). Marine and Freshwater Behaviour and Physiology.

https://doi.org/10.1080/10236244.2016.1168089

| The page says | The source says |
| :--- | :--- |
| used to pin stingrays to the seafloor | Specialized prey handling behavior of a great hammerhead was first described in detail by Strong et al. (1990). During this observation, a great hammerhead (~3.0 m TL) utilized its ... cephalofoil to pin a southern stingray, Dasyatis americana to the substrate (termed ‘pin and pivot’). A similar behavior was observed by Chapman and Gruber (2002) of a single great hammerhead (~3.6 m) capturing and consuming a spotted eagle ray (note: Two described events (1990 stingray, 2002 eagle ray); the reviewer replaced 'built to pin', which claimed a design purpose no source gives) |
| In 1990, scientists first described in detail how one used its head to pin a southern stingray to the seafloor, a move called "pin and pivot." | Specialized prey handling behavior of a great hammerhead was first described in detail by Strong et al. (1990). During this observation, a great hammerhead (~3.0 m TL) utilized its ... cephalofoil to pin a southern stingray, Dasyatis americana to the substrate (termed ‘pin and pivot’) |
| In 1990, scientists first described in detail how one great hammerhead used its head to pin a southern stingray to the seafloor, a move called "pin and pivot." | Specialized prey handling behavior of a great hammerhead was first described in detail by Strong et al. (1990). During this observation, a great hammerhead (~3.0 m TL) utilized its ... cephalofoil to pin a southern stingray, Dasyatis americana to the substrate (termed ‘pin and pivot’) |
| In 2002, scientists reported a similar move by a great hammerhead catching and eating a spotted eagle ray | A similar behavior was observed by Chapman and Gruber (2002) of a single great hammerhead (~3.6 m) capturing and consuming a spotted eagle ray |

## Stanhope et al. (2023). Genomes of endangered great hammerhead and shortfin mako sharks reveal historic population declines and high levels of inbreeding in great hammerhead. iScience.

https://doi.org/10.1016/j.isci.2022.105815

| The page says | The source says |
| :--- | :--- |
| worldwide | It has a worldwide distribution, found in coastal tropical and warm temperate seas |
| It lives in warm coastal seas around the world | It has a worldwide distribution, found in coastal tropical and warm temperate seas |
| mainly because it is fished heavily for its large fins | Its critically endangered status is primarily due to heavy fishing for its large fins, which are highly valued in the shark fin trade |
| Its global population is estimated to have fallen by more than 80% over the last three generations | global population reduction was recently estimated at >80% over the last 3 generations (note: The genome paper cites this estimate (its ref 30, Sherley et al., the JARA Red List tool); it is not the study's own, so 'The same study estimated' was cut) |
| A 2023 study read the genome, the full set of DNA, | Here, we present chromosome-level genome assemblies for the Critically Endangered great hammerhead (note: 2023 is the paper's publication year (iScience 26, 2023), as in the reference list) |
| of one great hammerhead from the North Atlantic | The North Atlantic population, from which our individual arose |
| It had low genetic variety | The great hammerhead exhibited low genetic variation |
| at the bottom of a broad list of fish species | Genome-wide heterozygosity estimates for white shark, whale shark, and hammerhead were at the bottom of those of a broad list of fish species (note: The source's 'below the majority of all but a selected few endangered species of mammals' is ambiguous, so the mammal comparison was cut) |
| signs of inbreeding (when parents are close relatives) as high as in some critically endangered animals | The inbreeding coefficient for hammerhead (FROH >1Mbp) was almost 9%, comparable to or exceeding other examples of critically endangered taxa |
| more sharks must be sampled before drawing firm conclusions about the whole species | Heterozygosity and ROH of the reference individual suggest low diversity and inbreeding even in this population; however, sampling additional individuals would be necessary before making any more definitive population- or species-level conclusions |
| Critically Endangered, mainly due to heavy fishing for its fins | chromosome-level genome assemblies for the Critically Endangered great hammerhead ... Its critically endangered status is primarily due to heavy fishing for its large fins, which are highly valued in the shark fin trade |
| A 2023 study of one great hammerhead's genome found low genetic variety | The great hammerhead exhibited low genetic variation (note: 2023 is the paper's publication year; 'one great hammerhead' is the study's single reference individual (next claim)) |
| and signs of inbreeding, though its authors say | Heterozygosity and ROH of the reference individual suggest low diversity and inbreeding even in this population; however, sampling additional individuals would be necessary |

## Doan & Kajiura (2020). Adult blacktip sharks (Carcharhinus limbatus) use shallow water as a refuge from great hammerheads (Sphyrna mokarran). Journal of Fish Biology.

https://doi.org/10.1111/jfb.14342

| The page says | The source says |
| :--- | :--- |
| Drone footage from southeast Florida shows adult blacktip sharks fleeing into shallow water when a great hammerhead comes after them | Aerial drone footage of blacktip sharks, Carcharhinus limbatus, along the coast of southeast Florida, USA, shows adult blacktips fleeing to the shallow water adjacent to the beach when confronted with or chased by a predatory great hammerhead shark |