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What the sources say

HippopotamusHippopotamus amphibius

Every figure, record and mechanism on the Hippopotamus profile was written from a source, and this is the working table behind it: 60 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

Animal Diversity Web, University of Michigan

Hippopotamus amphibius (hippopotamus). Animal Diversity Web, University of Michigan.

The page saysUsually shallow lakes, rivers and swamps, across Africa south of the Sahara
The source saysHippos are a semi-aquatic mammal, usually inhabiting shallow lakes, rivers, and swamps.Note: range: coughlin-fish-2009 'found throughout Africa south of the Sahara Desert'
The page saysRoughly 40 kg of grass grazed each night
The source saysthey are known to consume an enormous amount of food each night, 1-1.5% of their body weight (usually around 40 kg of food).
The page saysbut farther when food is scarce
The source saysthey will travel several kilometers when food is scarce
The page sayskept sharp by grinding
The source sayssharpening themselves as they grind their mouths together during grazing.
The page saysVulnerable
The source saysIUCN Red List Vulnerable
The page sayskept sharp as the teeth grind together during grazing
The source sayssharpening themselves as they grind their mouths together during grazing.
The page saysIt isn't blood, although it was long thought to be a mix of blood and sweat, which earned it the nickname "blood sweat."
The source saysFor years this fluid was thought to be a mixture of blood and sweat, giving it the nickname “blood sweat.” It is now known that this fluid is a combination of hipposudoric acid and norhipposudoric acid.
The page saysHippos have no sweat glands; mucous glands release the fluid instead
The source saysHippos lack scent and sweat glands. Instead, mucous glands secrete a thick oily layer of red pigmented fluid.
The page saysMost attacks on people and other animals come from females about to give birth or protecting their calves
The source saysMost attacks on humans and other animals are by females prior to birthing or when protecting their calves.
The page saysusually spends the day in shallow lakes, rivers and swamps
The source saysHippos are a semi-aquatic mammal, usually inhabiting shallow lakes, rivers, and swamps. ... During the daytime, herds prefer to sleep in shallow water
The page saysHippos have no sweat glands
The source saysHippos lack scent and sweat glands.
The page saysInstead, mucous glands release a thick fluid
The source saysInstead, mucous glands secrete a thick oily layer of red pigmented fluid.
The page saysFor years people thought it was a mix of blood and sweat, which earned it the nickname "blood sweat."
The source saysFor years this fluid was thought to be a mixture of blood and sweat, giving it the nickname “blood sweat.”
The page saysBesides people, adult hippos have no known predators
The source saysBesides humans, adult hippopotami have no known predators.
The page sayslions, hyenas and crocodiles occasionally prey on young ones
The source saysOccasionally lions, hyenas, and crocodiles will prey on young hippopotami.
The page saysHippos usually display dominance by yawning, roaring, dung showering and jaw clashing
The source saysDominance is usually displayed with yawning, roaring, dung showering, and jaw clashing.
The page saysHippos graze between four and five hours each night
The source saysGrazing lasts between four and five hours each night, covering between 3 and 4 km in circular patterns.
The page sayspulling up grass with muscular lips 50 cm wide
The source saysMuscular lips, 50 cm wide, are ideal to pull up grasses.
The page saysThey don't chew it with their teeth
The source saysHippos do not use their teeth to chew their meals
The page saysputting away roughly 40 kg, about 1 to 1.5 percent of body weight
The source saysthey are known to consume an enormous amount of food each night, 1-1.5% of their body weight (usually around 40 kg of food).
The page saysbefore heading back before dawn
The source saysHippos enter and exit their water pools at the same spot, returning from grazing before dawn.
The page saysFemales and calves hold the center of a resting pool while bulls guard its edges
The source saysFemales are the leaders of the herd, controlling the centers of the resting pools. Males rest along the outer banks of the pools, protecting the females and calves.
The page saysthe longest-lived hippo on record passed 61 years in captivity
The source saysThe longest living hippopotamus exceeded 61 years in captivity.
The page saysThe IUCN lists the species as Vulnerable
The source saysIUCN Red List Vulnerable
The page saysAnimal Diversity Web, citing the Red List, reports a 7 to 20 percent decline over ten years and an estimated 125,000 to 148,000 hippos in the wild
The source saysAccording to the IUNC Redlist, there has been a 7 to 20% decline in hippopotamus populations over the past 10 years. It was estimated that in the 29 countries within its geographic range, there are only between 125,000 to 148,000 individuals.

Source
02

San Diego Zoo Wildlife Alliance Library

Hippopotamus (Hippopotamus amphibius) & Pygmy Hippopotamus (Choerpsis liberiensis) Fact Sheet: Physical Characteristics. San Diego Zoo Wildlife Alliance Library.

The page saysA one-and-a-half-tonne river giant
The source saysMales: 1,546 kg (3,408 lb), on averageNote: 1.5 tonnes is the average bull
The page saysA bull's canine tusks keep growing for life
The source saysCanines and incisors enormously enlarged and continuously growing
The page sayscan reach 50 cm
The source saysMale canines can grow to 50 cm (1.5 ft)
The page saysa jaw that gapes 150 degrees, more than three times a human's 45
The source saysJaws hinged far to the back, allowing enormous gape of 150° (humans have only 45°)
The page saysA hippo's jaw hinges far enough back to gape open 150 degrees; a human manages only 45
The source saysJaws hinged far to the back, allowing enormous gape of 150° (humans have only 45°)
The page sayscan reach 50 centimeters
The source saysMale canines can grow to 50 cm (1.5 ft)
The page saysSan Diego Zoo Wildlife Alliance notes that hippos suffer many bite wounds from fighting, and the red pigment's antibiotic properties hold back harmful bacteria
The source saysHippos suffer many bite wounds from fighting, but red pigment's (“hipposudoric acid”) antibiotic properties inhibit pathogenic bacteria
The page saysBulls are heavier too: an average bull weighs around 1,546 kg and can reach about 2,065 kg, while cows average 1,385 kg
The source saysMales: 1,546 kg (3,408 lb), on average (up to approximately 2,065 kg, or 4,552 lb) ... Females: 1,385 kg (3,053 lb), on average

Source
03

San Diego Zoo Wildlife Alliance Library

Hippopotamus (Hippopotamus amphibius) & Pygmy Hippopotamus (Choerpsis liberiensis) Fact Sheet: Diet & Feeding. San Diego Zoo Wildlife Alliance Library.

The page saysusually within a few kilometers of water
The source saysUsually remain close (1-3 km or .6-1.9 mi) to home watercourse during nighttime feeding
The page saysThey usually stay within a few kilometers of water, though scarce grass can push them farther
The source saysUsually remain close (1-3 km or .6-1.9 mi) to home watercourse during nighttime feedingNote: farther when scarce: adw-hippo 'they will travel several kilometers when food is scarce'

Source
04

San Diego Zoo Wildlife Alliance Library

Hippopotamus (Hippopotamus amphibius) & Pygmy Hippopotamus (Choerpsis liberiensis) Fact Sheet: Reproduction & Development. San Diego Zoo Wildlife Alliance Library.

The page saysin accredited zoos hippos have a median lifespan around 36.6 years
The source saysMedian life expectancy 36.6 years (AZA 2023)

Source
05

Saikawa et al. 2004

Saikawa et al. (2004). The red sweat of the hippopotamus. Nature.

The page saysoozes its own sunscreen
The source sayshave antibiotic as well as sunscreen activity.
The page saysIt starts out colorless, then turns red within minutes and brown as it dries
The source saysWithin a few minutes of perspiration, the colourless, viscous sweat of the hippopotamus gradually turns red, and then brown as the pigment polymerizes.
The page saysThe chemists who isolated its two pigments, hipposudoric acid and norhipposudoric acid, found they have antibiotic as well as sunscreen activity
The source sayswe isolate and characterize the pigments responsible for this colour reaction ... have antibiotic as well as sunscreen activity.Note: pigment names: adw-hippo 'a combination of hipposudoric acid and norhipposudoric acid'

Source
06

Coughlin & Fish 2009

Coughlin & Fish (2009). Hippopotamus Underwater Locomotion: Reduced-Gravity Movements for a Massive Mammal. Journal of Mammalogy.

The page sayswalks the riverbed instead of swimming
The source sayswalks underwater rather than swims
The page saysHippos are denser than water
The source saysEffective bottom walking requires a body that is denser than water when submerged.
The page saysin a study that filmed two captive hippos underwater, researchers never once caught them swimming
The source saysThe animals were never observed to swim in the water.Note: two captive hippos: 'Two adult female hippopotami were observed at the Adventure Aquarium'
The page sayspush off the riverbed in a slow, gliding gallop with long unsupported "in flight" moments between steps
The source saysperiods in which the hippopotami are ''in flight'' with no feet in contact with the ground
The page saysa gait researchers call underwater "punting."
The source saysThis type of aquatic pedestrian locomotion has been referred to as ''punting.''
The page saysThat density is also why a hippo can walk the bottom rather than bob to the surface
The source saysMaintenance of foot contact with the bottom is accomplished by control of the specific gravity of the body and high bone density
The page saysholding its breath for up to 30 minutes
The source saysH. amphibius can remain submerged for up to 30 min
The page saysfound throughout Africa south of the Sahara Desert
The source saysis a semi- aquatic mammal that is found throughout Africa south of the Sahara Desert in rivers and lakes surrounded by grasslands and reedbedsNote: hand-checked in the authors' open-access PDF (scratch/hippo-coughlin-fish-2009-extracted.txt)
The page saysit walks underwater rather than swims
The source sayswalks underwater rather than swims
The page saysResearchers who filmed two captive hippos underwater never once saw them swim
The source saysThe animals were never observed to swim in the water.
The page sayspush off the bottom in a slow-motion gallop, gliding through long unsupported "in flight" moments between footfalls
The source saysperiods in which the hippopotami are ''in flight'' with no feet in contact with the groundNote: gallop: 'The gait of the hippopotamus resembled an extended gallop'
The page saysa gait the researchers compare to moving in microgravity
The source saystion of the hippopotamus underwater is analogous to movement in a microgravity environmentNote: hand-checked in the PDF text, where 'locomotion' is split across a line
The page saysDense, heavy limb bones keep a hippo's body denser than water, so it stays glued to the riverbed instead of floating up
The source saysMaintenance of foot contact with the bottom is accomplished by control of the specific gravity of the body and high bone density ... Effective bottom walking requires a body that is denser than water when submerged.
The page saysable to hold its breath for up to 30 minutes at a stretch
The source saysH. amphibius can remain submerged for up to 30 min
The page sayspushing off the bottom in a slow-motion gallop and gliding through long moments with no feet touching the ground
The source saysperiods in which the hippopotami are ''in flight'' with no feet in contact with the groundNote: vibe.reason (#692/#693)
The page saysit walks rather than swims
The source sayswalks underwater rather than swimsNote: vibe.reason (#692/#693)

Source
07

Haddara et al. 2020

Haddara et al. (2020). Hippopotamus bite morbidity: a report of 11 cases from Burundi. Oxford Medical Case Reports.

The page saysDoctors in Burundi who treated eleven hippo-bite patients called the species aggressive and dangerous
The source saysHippopotamus is one of the most-loved animals in Africa, yet it is aggressive and dangerous.Note: eleven patients: 'We present a cohort of 11 patients who suffered hippopotamus bite injuries in Burundi.'
The page sayswound infections, amputations and permanent disability among the outcomes
The source saysThe results show a high incidence of wound infections, amputations and permanent disability among other complications.

Source
08

Hutchinson & Pringle 2024

Hutchinson & Pringle (2024). Footfall patterns and stride parameters of Common hippopotamus (Hippopotamus amphibius) on land. PeerJ.

The page saysOn land, hippos are often said to reach about 30 km/h, but a 2024 study points out that their top speed has not been reliably measured
The source saysMaximal speeds have not been reliably measured but have been claimed (without empirical documentation) at up to ... 30 kphNote: 2024 is the study's publication year (Hutchinson et al. 2024)
The page saysIts survey of 32 hippos on video found every one trotting or nearly trotting
The source saysgathering a sample of 169 strides from 32 hippos. No hippos studied used other than trotting (or near-trotting) footfall patterns
The page saysat their fastest relative speeds they were briefly airborne mid-stride, apparently a new discovery
The source saysat the fastest relative speeds hippos used brief aerial phases, apparently a new discovery.

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.