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What the sources say

Bull SharkCarcharhinus leucas

Every figure, record and mechanism on the Bull Shark profile was written from a source, and this is the working table behind it: 40 claims checked word for word against these sources. The left column is what the page says. The right column is the source's own words, copied, not paraphrased; a ... marks a cut and[brackets] an insertion. Open any source and check it yourself.

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Source
01

Florida Museum of Natural History, Ichthyology

Carcharhinus leucas. Florida Museum of Natural History, Ichthyology.

The page saysFreshwater river invader
The source saysIt is one of very few species that readily move into freshwater
The page saysnamed for its stout build and a reputation for aggression
The source saysThe bull shark name derives from its stout appearance and reputation for aggressive behavior.
The page saysWarm coastal shallows, murky estuaries, tropical harbors
The source saysBull sharks occur in tropical to subtropical coastal waters, worldwide. ... The bull shark prefers to live in shallow coastal waters less than 100 feet deep (30 m) ... It commonly enters estuaries, bays, harbors, lagoons, and river mouths. ... vision may not be as important for this species which often occurs in turbid waters.
The page saysrivers such as the Amazon and Mississippi, up which it has been reported more than 1,800 miles
The source saysThey have been reported 3700 km (2220 mi) up the Amazon River in Peru, and over 3000 km (1800 mi) up the Mississippi River, in Illinois.Note: stats.habitat. 3,000 km is about 1,860 miles and 3,700 km about 2,300 miles, so 'more than 1,800 miles' holds for both rivers.
The page saysMostly bony fish and small sharks, plus stingrays, with sea turtles, dolphins, crabs, shrimp, sea birds and even dogs occasionally reported
The source saysBony fishes and small sharks make up the vast majority ... They also consume stingrays and juvenile sharks including small individuals of their own species in their inshore nursery habitats. Other food items occasionally reported in bull sharks include sea turtles, dolphins, crabs, shrimp, sea birds, squid, and dogs.
The page saysBull sharks (Carcharhinus leucas) live in tropical to subtropical coastal waters around the world, preferring shallows less than 30 meters (100 feet) deep
The source saysBull sharks occur in tropical to subtropical coastal waters, worldwide. ... The bull shark prefers to live in shallow coastal waters less than 100 feet deep (30 m)
The page saysThey commonly push into estuaries, bays, harbors, lagoons and river mouths, and they are one of very few sharks that readily move into freshwater
The source saysIt commonly enters estuaries, bays, harbors, lagoons, and river mouths. It is one of very few species that readily move into freshwater
The page saysThey have been reported 3,700 kilometers (about 2,300 miles) up the Amazon River in Peru and more than 3,000 kilometers (1,800 miles) up the Mississippi, in Illinois
The source saysThey have been reported 3700 km (2220 mi) up the Amazon River in Peru, and over 3000 km (1800 mi) up the Mississippi River, in Illinois.Note: The museum's '2220 mi' is a conversion slip: 3,700 km is about 2,300 miles. The page gives the kilometer figure the museum reports and its correct conversion.
The page saysThe bull sharks of Lake Nicaragua were once thought to be trapped there, until researchers found they reach the ocean through a system of rivers and estuaries
The source saysA population in Lake Nicaragua (Central America) was once thought to be landlocked, but it was subsequently determined that they gain access to the ocean through a system of rivers and estuaries.
The page saysBull sharks are found in both salt and fresh water
The source saysThese large stout sharks are found in both salt and fresh water.
The page saysthey can also tolerate hypersaline water, saltier than the sea, as high as 53 parts per thousand
The source saysBull sharks can also tolerate hypersaline water as high as 53 parts per thousandNote: 'Saltier than the sea' glosses 'hypersaline', which means saltier than seawater.
The page saysThe name comes from the shark's stout build and its reputation for aggressive behavior
The source saysThe bull shark name derives from its stout appearance and reputation for aggressive behavior.
The page saysBull sharks are thick-bodied with a blunt, rounded snout
The source saysBull sharks are very stout-bodied and have a blunt, rounded snout.
The page sayscan grow to about 3.4 meters (11 feet) long
The source saysBull sharks can grow to a total length of about 340 cm.Note: 340 cm = 3.4 m, about 11.2 feet.
The page saysthe longest reported measured 4 meters (13 feet)
The source saysThe maximum reported length of the bull shark is 400 cm (~13 ft)Note: 400 cm = 4 m. The 2023 FRDC report card also gives a maximum of 400 cm TL (McCord and Lamberth 2009).
The page saysTheir eyes are smaller than those of most other requiem sharks, which suggests vision may matter less to a species that often lives in murky water
The source saysBull sharks have small eyes relative to most other carcharhinid sharks which suggests that vision may not be as important for this species which often occurs in turbid waters.Note: Carcharhinids (family Carcharhinidae) are the requiem sharks.
The page saysBony fish and small sharks make up the vast majority of the diet, and in inshore nurseries they also eat stingrays and young sharks, including small bull sharks
The source saysBony fishes and small sharks make up the vast majority ... They also consume stingrays and juvenile sharks including small individuals of their own species in their inshore nursery habitats.
The page saysThey look sluggish cruising along the bottom, and have been recorded moving at over 19 km/h (11 mph) in short bursts
The source saysBull sharks appear sluggish as they cruise slowly along the bottom, but are capable of quick bursts that allow them to capture smaller, agile prey. They have been recorded to move at over 11 mph (19 km/h) over short distances.
The page saysThe Florida Museum's bull shark profile notes it is harder to identify than a white or tiger shark, so it may be behind a large fraction of the attacks that go unassigned to a species
The source saysThe Bull shark is also not as readily identified as is the white shark or the tiger shark, and so may be responsible for a large fraction of the of the attacks that go unassigned to species
The page saysIt also says the bull shark is considered by many to be the most dangerous shark in the world, and that its large size, liking for freshwater, abundance and closeness to people, especially in the tropics, make it more of a potential threat than the white or tiger shark
The source saysIt is considered by many to be the most dangerous shark in the world. It’s large size, proclivity for freshwater, abundance and proximity to human populations, particularly in the tropics, makes it more of a potential threat than is either the White shark or the Tiger shark.

Source
02

Habegger et al. 2012

Habegger et al. (2012). Feeding biomechanics and theoretical calculations of bite force in bull sharks (Carcharhinus leucas) during ontogeny. Zoology.

The page sayswith a harder bite for its weight than a great white's
The source saysWhen the bite force of C. leucas was compared to those of 12 other cartilaginous fishes, bull sharks presented the highest mass-specific bite force, greater than that of the white shark or the great hammerhead shark.Note: Tagline. Mass-specific (per body mass) theoretical bite force, compared across 13 cartilaginous fishes.
The page saysA 2012 study calculated the bite force of bull sharks 73 to 285 centimeters long
The source sayswe investigated biting performance and feeding biomechanics of immature and mature individuals from an ontogenetic series of an apex predator, the bull shark, Carcharhinus leucas (73-285cm total length). Theoretical bite force ranged from 36 to 2128N at the most anterior bite point, and 170 to 5914N at the most posterior bite point over the ontogenetic series.Note: 2012 is the paper's publication year (Habegger et al. 2012, Zoology). Body and FAQ 3 use the same sentence.
The page saysAt the back of the jaws, the theoretical bite ranged from 170 to 5,914 newtons, about 1,330 pounds of force at the top end
The source saysTheoretical bite force ranged from 36 to 2128N at the most anterior bite point, and 170 to 5914N at the most posterior bite point over the ontogenetic series.Note: 5,914 N / 4.448 = 1,330 pounds of force. Body and FAQ 3 use the same sentence.
The page saysCompared with 12 other cartilaginous fishes, bull sharks had the highest bite force for their body mass, beating the great white and the great hammerhead
The source saysWhen the bite force of C. leucas was compared to those of 12 other cartilaginous fishes, bull sharks presented the highest mass-specific bite force, greater than that of the white shark or the great hammerhead shark.
The page saysCompared with 12 other cartilaginous fishes, bull sharks had the highest bite force for their body mass, greater than that of the great white or the great hammerhead
The source saysWhen the bite force of C. leucas was compared to those of 12 other cartilaginous fishes, bull sharks presented the highest mass-specific bite force, greater than that of the white shark or the great hammerhead shark.

Source
03

Pillans & Franklin 2004

Pillans & Franklin (2004). Plasma osmolyte concentrations and rectal gland mass of bull sharks Carcharhinus leucas, captured along a salinity gradient. Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology.

The page saysBlood chemistry that shifts with the water: bull sharks caught in freshwater carried about half the blood urea of those caught at sea
The source saysBull sharks (Carcharhinus leucas) were captured across a salinity gradient from freshwater (FW) to seawater (SW). ... In FW animals, sodium, chloride and urea were 208 +/- 3, 203 +/- 3 and 192 +/- 2 mmol l(-1), respectively. Plasma sodium, chloride and urea in SW-captured C. leucas were 289 +/- 3, 296 +/- 6 and 370 +/- 10 mmol l(-1), respectively.Note: stats.superpower. 192 / 370 = 52%, so 'about half'.
The page saysA study that caught bull sharks along a gradient from freshwater to seawater found the freshwater sharks carried about half as much urea in their blood: 192 millimoles per liter, against 370 in sharks from the sea
The source saysBull sharks (Carcharhinus leucas) were captured across a salinity gradient from freshwater (FW) to seawater (SW). ... In FW animals, sodium, chloride and urea were 208 +/- 3, 203 +/- 3 and 192 +/- 2 mmol l(-1), respectively. Plasma sodium, chloride and urea in SW-captured C. leucas were 289 +/- 3, 296 +/- 6 and 370 +/- 10 mmol l(-1), respectively.Note: 192 / 370 = 52%.
The page saysTheir sodium and chloride were lower too, yet at every salinity their blood stayed more concentrated than the water outside
The source saysAcross all salinities, C. leucas were hyperosmotic to the environment. ... In FW animals, sodium, chloride and urea were 208 +/- 3, 203 +/- 3 and 192 +/- 2 mmol l(-1), respectively. Plasma sodium, chloride and urea in SW-captured C. leucas were 289 +/- 3, 296 +/- 6 and 370 +/- 10 mmol l(-1), respectively.
The page saysUrea rose sharply between 28 and 33 parts per thousand of salt
The source sayslargely due to a sharp increase in plasma urea between 28 per thousand and 33 per thousand
The page saysa study that sampled them from freshwater to seawater measured plasma urea of about 192 millimoles per liter in freshwater sharks against 370 in sharks caught at sea, with sodium and chloride lower in freshwater too
The source saysBull sharks (Carcharhinus leucas) were captured across a salinity gradient from freshwater (FW) to seawater (SW). ... In FW animals, sodium, chloride and urea were 208 +/- 3, 203 +/- 3 and 192 +/- 2 mmol l(-1), respectively. Plasma sodium, chloride and urea in SW-captured C. leucas were 289 +/- 3, 296 +/- 6 and 370 +/- 10 mmol l(-1), respectively.
The page saysEven in freshwater, their blood stayed more concentrated than the water around them
The source saysAcross all salinities, C. leucas were hyperosmotic to the environment.

Source
04

Reilly et al. 2011

Reilly et al. (2011). Branchial osmoregulation in the euryhaline bull shark, Carcharhinus leucas: a molecular analysis of ion transporters. Journal of Experimental Biology.

The page saysIn sharks and rays that move between salt and fresh water, the kidneys, rectal gland and liver work together to handle the change
The source saysOsmoregulation in euryhaline elasmobranchs is achieved through the control and integration of various organs (kidney, rectal gland and liver) in response to changes in environmental salinity.Note: 'Sharks and rays that move between salt and fresh water' for euryhaline elasmobranchs.
The page saysIn the gills of bull sharks caught in freshwater, the genes for two sodium-handling transporters were more active than in sharks from saltier water, which may help the gills take up sodium in freshwater
The source saysquantitative real-time PCR showed that the mRNA expression of NHE3 and NKA was significantly upregulated in gills of FW-captured C. leucas relative to EST/SW-captured animals. These data suggest that NHE3 and NKA together may be important in mediating branchial Na(+) uptake in freshwater environmentsNote: NKA is the Na+/K+-ATPase and NHE3 the Na+/H+ exchanger 3, both named for the sodium they move. 'Genes ... more active' for upregulated mRNA expression; 'saltier water' for estuarine/seawater.
The page saysIn sharks and rays that move between salt and fresh water, the kidneys, rectal gland and liver work together to manage the change
The source saysOsmoregulation in euryhaline elasmobranchs is achieved through the control and integration of various organs (kidney, rectal gland and liver) in response to changes in environmental salinity.

Source
05

Shark and Ray Report Card, Fisheries Research and Development Corporation

Bull Shark, Carcharhinus leucas Report Card. Shark and Ray Report Card, Fisheries Research and Development Corporation.

The page saysVulnerable
The source saysit is assessed globally as Vulnerable (IUCN)Note: stats.conservationStatus. Read by hand from the PDF (page 1): the report card's table reads 'IUCN Red List Global Assessment Vulnerable', and its references give Rigby et al. 2021, The IUCN Red List of Threatened Species 2021: e.T39372A2910670. Florida Museum and ADW still show the 2009 Near Threatened assessment.

Source
06

Hazon et al. 2003

Hazon et al. (2003). Urea based osmoregulation and endocrine control in elasmobranch fish with special reference to euryhalinity. Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology.

The page saysSharks and rays hold on to a chemical called urea, so their body fluids are as concentrated as the seawater around them, or slightly more
The source saysSmith recognised that urea was retained in the body fluids as part of the 'osmoregulatory ballast' of elasmobranch fish so that body fluid osmolality is raised to a level that is iso- or slightly hyper-osmotic to that of the surrounding medium.Note: 'Sharks and rays' for elasmobranchs; 'as concentrated as ... or slightly more' for iso- or slightly hyper-osmotic.
The page saysSharks and rays keep urea in their body fluids so they are as concentrated as seawater, or slightly more
The source saysSmith recognised that urea was retained in the body fluids as part of the 'osmoregulatory ballast' of elasmobranch fish so that body fluid osmolality is raised to a level that is iso- or slightly hyper-osmotic to that of the surrounding medium.
The page saysBull sharks can adjust that
The source saysa fully euryhaline elasmobranch, the bull shark, Carcharhinus leucas ... Both partially euryhaline and fully euryhaline species utilise the same physiological processes to control urea, Na(+) and Cl(-) levels within the body fluids.

Source
07

International Shark Attack File, Florida Museum of Natural History

Species Implicated in Attacks. International Shark Attack File, Florida Museum of Natural History.

The page saysThe International Shark Attack File names the bull shark with the white and tiger sharks as the Big Three of shark attacks: large species that can inflict serious injuries, are common where people enter the water, and have teeth designed to shear rather than hold
The source saysthe white, tiger and bull sharks are the “Big Three” in the shark attack world because they are large species that are capable of inflicting serious injuries to a victim, are commonly found in areas where humans enter the water, and have teeth designed to shear rather than hold.
The page saysIts species table, last updated in 2022, lists 119 confirmed unprovoked attacks by bull sharks, 26 of them fatal
The source saysSpecies of shark implicated in confirmed unprovoked attacks around the world Species Common Name Non-fatal Unprovoked Fatal Unprovoked Total ... Carcharhinus leucas Bull 93 26 119 ... Page Last Updated: 01/25/2022Note: Columns: 93 non-fatal, 26 fatal, 119 total. The Florida Museum species profile's older figure (at least 100 attacks, 27 fatal, ISAF 2018) is superseded by this table.

How the table was made: a writer drafted the profile from these sources and logged each claim with its quote, a reviewer with nothing but this table checked every sentence said no more than its quote, and a script confirmed each quote appears word for word in the source. The method is in the site'sAbout page.