---
title: "What the sources say about the Hippopotamus | AnimalTracks.wiki"
description: "60 claims from the Hippopotamus profile, each beside the words of the source that backs it."
image: "https://animaltracks.wiki/images/animals/hippopotamus-1.webp"
canonical: "https://animaltracks.wiki/animals/hippopotamus/sources/"
---

# What the sources say about the Hippopotamus (*Hippopotamus amphibius*)

> 60 claims from the Hippopotamus profile, each beside the words of the source that backs it. A "..." marks a cut in a quote and [brackets] an insertion.

Profile: [Hippopotamus](https://animaltracks.wiki/animals/hippopotamus/)

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

https://animaldiversity.org/accounts/Hippopotamus_amphibius/

| The page says | The source says |
| :--- | :--- |
| Usually shallow lakes, rivers and swamps, across Africa south of the Sahara | Hippos 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') |
| Roughly 40 kg of grass grazed each night | they are known to consume an enormous amount of food each night, 1-1.5% of their body weight (usually around 40 kg of food). |
| but farther when food is scarce | they will travel several kilometers when food is scarce |
| kept sharp by grinding | sharpening themselves as they grind their mouths together during grazing. |
| Vulnerable | IUCN Red List Vulnerable |
| kept sharp as the teeth grind together during grazing | sharpening themselves as they grind their mouths together during grazing. |
| It isn't blood, although it was long thought to be a mix of blood and sweat, which earned it the nickname "blood sweat." | For 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. |
| Hippos have no sweat glands; mucous glands release the fluid instead | Hippos lack scent and sweat glands. Instead, mucous glands secrete a thick oily layer of red pigmented fluid. |
| Most attacks on people and other animals come from females about to give birth or protecting their calves | Most attacks on humans and other animals are by females prior to birthing or when protecting their calves. |
| usually spends the day in shallow lakes, rivers and swamps | Hippos are a semi-aquatic mammal, usually inhabiting shallow lakes, rivers, and swamps. ... During the daytime, herds prefer to sleep in shallow water |
| Hippos have no sweat glands | Hippos lack scent and sweat glands. |
| Instead, mucous glands release a thick fluid | Instead, mucous glands secrete a thick oily layer of red pigmented fluid. |
| For years people thought it was a mix of blood and sweat, which earned it the nickname "blood sweat." | For years this fluid was thought to be a mixture of blood and sweat, giving it the nickname “blood sweat.” |
| Besides people, adult hippos have no known predators | Besides humans, adult hippopotami have no known predators. |
| lions, hyenas and crocodiles occasionally prey on young ones | Occasionally lions, hyenas, and crocodiles will prey on young hippopotami. |
| Hippos usually display dominance by yawning, roaring, dung showering and jaw clashing | Dominance is usually displayed with yawning, roaring, dung showering, and jaw clashing. |
| Hippos graze between four and five hours each night | Grazing lasts between four and five hours each night, covering between 3 and 4 km in circular patterns. |
| pulling up grass with muscular lips 50 cm wide | Muscular lips, 50 cm wide, are ideal to pull up grasses. |
| They don't chew it with their teeth | Hippos do not use their teeth to chew their meals |
| putting away roughly 40 kg, about 1 to 1.5 percent of body weight | they are known to consume an enormous amount of food each night, 1-1.5% of their body weight (usually around 40 kg of food). |
| before heading back before dawn | Hippos enter and exit their water pools at the same spot, returning from grazing before dawn. |
| Females and calves hold the center of a resting pool while bulls guard its edges | Females 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 longest-lived hippo on record passed 61 years in captivity | The longest living hippopotamus exceeded 61 years in captivity. |
| The IUCN lists the species as Vulnerable | IUCN Red List Vulnerable |
| Animal 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 | According 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. |

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

https://ielc.libguides.com/sdzg/factsheets/hippopotamus/characteristics

| The page says | The source says |
| :--- | :--- |
| A one-and-a-half-tonne river giant | Males: 1,546 kg (3,408 lb), on average (note: 1.5 tonnes is the average bull) |
| A bull's canine tusks keep growing for life | Canines and incisors enormously enlarged and continuously growing |
| can reach 50 cm | Male canines can grow to 50 cm (1.5 ft) |
| a jaw that gapes 150 degrees, more than three times a human's 45 | Jaws hinged far to the back, allowing enormous gape of 150° (humans have only 45°) |
| A hippo's jaw hinges far enough back to gape open 150 degrees; a human manages only 45 | Jaws hinged far to the back, allowing enormous gape of 150° (humans have only 45°) |
| can reach 50 centimeters | Male canines can grow to 50 cm (1.5 ft) |
| San Diego Zoo Wildlife Alliance notes that hippos suffer many bite wounds from fighting, and the red pigment's antibiotic properties hold back harmful bacteria | Hippos suffer many bite wounds from fighting, but red pigment's (“hipposudoric acid”) antibiotic properties inhibit pathogenic bacteria |
| Bulls are heavier too: an average bull weighs around 1,546 kg and can reach about 2,065 kg, while cows average 1,385 kg | Males: 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 |

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

https://ielc.libguides.com/sdzg/factsheets/hippopotamus/diet

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

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

https://ielc.libguides.com/sdzg/factsheets/hippopotamus/reproduction

| The page says | The source says |
| :--- | :--- |
| in accredited zoos hippos have a median lifespan around 36.6 years | Median life expectancy 36.6 years (AZA 2023) |

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

https://doi.org/10.1038/429363a

| The page says | The source says |
| :--- | :--- |
| oozes its own sunscreen | have antibiotic as well as sunscreen activity. |
| It starts out colorless, then turns red within minutes and brown as it dries | Within a few minutes of perspiration, the colourless, viscous sweat of the hippopotamus gradually turns red, and then brown as the pigment polymerizes. |
| The chemists who isolated its two pigments, hipposudoric acid and norhipposudoric acid, found they have antibiotic as well as sunscreen activity | we 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') |

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

https://doi.org/10.1644/08-MAMM-A-279R.1

| The page says | The source says |
| :--- | :--- |
| walks the riverbed instead of swimming | walks underwater rather than swims |
| Hippos are denser than water | Effective bottom walking requires a body that is denser than water when submerged. |
| in a study that filmed two captive hippos underwater, researchers never once caught them swimming | The animals were never observed to swim in the water. (note: two captive hippos: 'Two adult female hippopotami were observed at the Adventure Aquarium') |
| push off the riverbed in a slow, gliding gallop with long unsupported "in flight" moments between steps | periods in which the hippopotami are ''in flight'' with no feet in contact with the ground |
| a gait researchers call underwater "punting." | This type of aquatic pedestrian locomotion has been referred to as ''punting.'' |
| That density is also why a hippo can walk the bottom rather than bob to the surface | Maintenance of foot contact with the bottom is accomplished by control of the specific gravity of the body and high bone density |
| holding its breath for up to 30 minutes | H. amphibius can remain submerged for up to 30 min |
| found throughout Africa south of the Sahara Desert | is a semi- aquatic mammal that is found throughout Africa south of the Sahara Desert in rivers and lakes surrounded by grasslands and reedbeds (note: hand-checked in the authors' open-access PDF (scratch/hippo-coughlin-fish-2009-extracted.txt)) |
| it walks underwater rather than swims | walks underwater rather than swims |
| Researchers who filmed two captive hippos underwater never once saw them swim | The animals were never observed to swim in the water. |
| push off the bottom in a slow-motion gallop, gliding through long unsupported "in flight" moments between footfalls | periods in which the hippopotami are ''in flight'' with no feet in contact with the ground (note: gallop: 'The gait of the hippopotamus resembled an extended gallop') |
| a gait the researchers compare to moving in microgravity | tion of the hippopotamus underwater is analogous to movement in a microgravity environment (note: hand-checked in the PDF text, where 'locomotion' is split across a line) |
| Dense, heavy limb bones keep a hippo's body denser than water, so it stays glued to the riverbed instead of floating up | Maintenance 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. |
| able to hold its breath for up to 30 minutes at a stretch | H. amphibius can remain submerged for up to 30 min |
| pushing off the bottom in a slow-motion gallop and gliding through long moments with no feet touching the ground | periods in which the hippopotami are ''in flight'' with no feet in contact with the ground (note: vibe.reason (#692/#693)) |
| it walks rather than swims | walks underwater rather than swims (note: vibe.reason (#692/#693)) |

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

https://doi.org/10.1093/omcr/omaa061

| The page says | The source says |
| :--- | :--- |
| Doctors in Burundi who treated eleven hippo-bite patients called the species aggressive and dangerous | Hippopotamus 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.') |
| wound infections, amputations and permanent disability among the outcomes | The results show a high incidence of wound infections, amputations and permanent disability among other complications. |

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

https://doi.org/10.7717/peerj.17675

| The page says | The source says |
| :--- | :--- |
| On 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 | Maximal speeds have not been reliably measured but have been claimed (without empirical documentation) at up to ... 30 kph (note: 2024 is the study's publication year (Hutchinson et al. 2024)) |
| Its survey of 32 hippos on video found every one trotting or nearly trotting | gathering a sample of 169 strides from 32 hippos. No hippos studied used other than trotting (or near-trotting) footfall patterns |
| at their fastest relative speeds they were briefly airborne mid-stride, apparently a new discovery | at the fastest relative speeds hippos used brief aerial phases, apparently a new discovery. |