The hippopotamus has the largest mouth of any land mammal, the longest teeth of any land animal that are not classified as tusks, and a bite force capable of snapping a fibreglass boat hull in half. It also has no use for any of this when eating. The hippo’s extraordinary dental anatomy was not designed for feeding — it was designed almost entirely for fighting, and it is one of the most specialised weapons in the animal kingdom.
Hippo Teeth: Quick Facts
| Feature | Common Hippo | Pygmy Hippo |
|---|---|---|
| Total teeth | 36 | 34 |
| Incisor pairs | 2 pairs (lower jaw) | 1 pair |
| Lower canine length | Up to 50 cm (20 in) | Up to 5 cm (2 in) |
| Upper canine length | Up to 30 cm (12 in) | Smaller |
| Longest canine recorded | 122 cm (48 in) | — |
| Bite force | ~1,800 PSI (8,100 N) | ~1,800 PSI |
| Jaw opening angle | 150–180 degrees | Less wide |
| Mouth width (fully open) | ~120 cm (4 ft) | Smaller |
| Tooth material | Ivory (hypselodont) | Ivory |
| Teeth used for eating | Molars and lips only | Molars and lips |
How Many Teeth Does a Hippo Have?
A common hippopotamus has 36 teeth in total:
- 8 incisors (4 upper, 4 lower)
- 4 canines (2 upper, 2 lower) — the tusks
- 12 premolars (6 upper, 6 lower)
- 12 molars (6 upper, 6 lower)
The dental formula for each side of the jaw is: 2 incisors, 1 canine, 3 premolars, 3 molars.
Some individual hippos have more than 36 teeth. Hippos can retain their deciduous (baby) teeth even after permanent teeth have erupted — an uncommon trait in mammals — which in some cases results in extra incisors or canines remaining alongside the permanent set.
The pygmy hippopotamus typically has 34 teeth: it has only one pair of lower incisors, compared to the common hippo’s two pairs.
The Canine Teeth: Nature’s Most Formidable Tusks
The hippopotamus’s most visually striking anatomical feature is its canine teeth. These are the long, curved, ivory teeth that protrude from the lower jaw — commonly called tusks, though technically canines — and they are among the most extraordinary dental structures in the animal kingdom.
Size and Growth
The lower canines of a common hippo typically grow to 40–50 cm (16–20 inches) in length. The upper canines, which point downward, reach approximately 25–30 cm (10–12 inches).
In exceptional individuals, the lower canines grow considerably longer. The Guinness Book of World Records documents a typical maximum of around 71 cm (28 inches), and the longest single hippo canine ever recorded measured an extraordinary 122 cm (48 inches) — just over four feet.
Canines grow continuously throughout the hippo’s life. They are hypselodont — high-crowned, ever-growing teeth — meaning they are never lost to natural wear. The older the hippo, the longer the canines, which is why very large, dominant bulls carry the most impressive tusks.
Self-Sharpening
The canines sharpen themselves through natural use. As the jaw opens and closes, the upper and lower canines grind against each other in a precise alignment, honing their edges continuously. This self-sharpening mechanism means a hippo’s tusks do not become blunt with age — they remain effective weapons throughout the animal’s life.
What Are Hippo Canines Made Of?
Hippo canines are composed of ivory — the same dense, mineralised material as elephant tusks, though with a different chemical composition. Hippo ivory is denser and initially whiter than elephant ivory, and it maintains its whiteness better over time. In the historical ivory trade, hippo ivory was used extensively for items requiring white ivory — including piano keys and decorative carvings — and was considered superior to elephant ivory for some applications.
The trade in hippo ivory is regulated under CITES (Convention on International Trade in Endangered Species). However, as elephant ivory bans have become more effective, poaching pressure on hippos for their ivory has increased. Hippo teeth can be bought and sold legally as antiques in some jurisdictions, and illegal trade in fresh hippo ivory — extracted from poached animals — is a growing conservation concern.
Hippo Bite Force: 1,800 PSI
The bite force of the common hippopotamus is measured at approximately 1,800 PSI (pounds per square inch), equivalent to 8,100 Newtons of force.
This measurement was obtained by wildlife researcher Dr. Brady Barr during filming for National Geographic’s “Dangerous Encounters” programme. Barr measured the bite force of a female hippo — the most cooperative subject available, since male hippos were considered too dangerous to test — recording 8,100 Newtons, which converts to approximately 1,821 lbf.
Critically, this was a female measurement. Male hippos have heads that are 44% heavier than females, with proportionally larger jaw muscles. The actual bite force of a large adult male hippo has never been directly measured, but is believed to be substantially higher than the female figure.
How Does 1,800 PSI Compare?
| Animal | Bite Force |
|---|---|
| Human | ~160 PSI |
| Dog (large breed) | ~300–400 PSI |
| Lion | ~650 PSI |
| Tiger | ~1,050 PSI |
| Polar bear | ~1,200 PSI |
| Hippopotamus | ~1,800 PSI |
| Gorilla | ~1,300 PSI |
| Nile crocodile | ~3,700–5,000 PSI |
| Saltwater crocodile | ~3,700 PSI |
| Great white shark | ~4,000 PSI |
At 1,800 PSI, the hippo has roughly:
- 11 times the bite force of a human
- nearly 3 times that of a lion
- 1.5 times that of a polar bear
Only the largest crocodilians and certain shark species exceed it among living animals. However, as noted in the hippo vs crocodile comparison, raw bite force is only one factor: the width of the hippo’s jaw opening and the size of its canines mean that even at lower PSI than a crocodile, a hippo bite causes catastrophic physical damage.
Jaw Anatomy: How Wide Does a Hippo’s Mouth Open?
The hippo’s jaw can open to 150–180 degrees, compared to a human’s maximum of approximately 45 degrees. At full gape, the mouth measures approximately 90–120 cm (3–4 feet) wide from corner to corner.
This extreme gape is not simply for show. It serves two mechanical purposes:
First, it maximises leverage. The muscles that close the jaw — primarily the temporalis and masseter muscles, which are extremely well-developed in hippos — generate force over a wide arc of motion. The wider the opening, the greater the mechanical advantage when the jaw closes, amplifying the effective bite force.
Second, it functions as a threat display. The hippo “yawn” — the dramatic wide opening of the mouth that exposes all teeth — is a deliberate warning signal. It is the hippo equivalent of a raised fist, communicating threat without requiring physical contact. In most wild encounters, a hippo that yawns is issuing a warning: leave the territory, or the next response will be a charge and a bite.
Wildlife observers and guides learn to read the yawn as an early warning system. The sequence is typically: yawning and head-swinging → vocalisation (honks, grunts) → mock charges → real charge. Recognising the early stages of this sequence can be life-saving.
What Hippos Do Not Use Their Teeth For: Eating
Perhaps the most counter-intuitive fact about hippo teeth is that the most impressive ones — the enormous canines and long incisors — are never used to eat. Hippos are herbivores. Their diet consists almost entirely of grass, supplemented by some leaves, fallen fruit, and aquatic vegetation.
To eat, hippos use:
Their lips — thick, wide, muscular lips that can grip large quantities of grass and pull it free from the ground with a sharp jerk of the head.
Their molars — the grinding teeth at the back of the jaw. These are the teeth that do all the work of processing food.
The large incisors in the front of the jaw actually prevent side-to-side grinding: because upper and lower incisors interlock tightly when the jaw closes, the lower jaw can only move vertically, not laterally. This restricts the hippo’s chewing efficiency considerably. Hippos process grass roughly rather than grinding it fine — they mash it somewhat and swallow it to a three-chambered digestive system that ferments the vegetation in a manner similar to that of true ruminants, though hippos do not chew cud.
This means that despite having one of the most powerful bites of any land mammal, the hippo’s extraordinary jaw is essentially a weapon that also happens to accommodate some molars for eating. The teeth drive social order, not dinner.
How Hippos Use Their Teeth in the Wild
Territorial Fighting
The primary use of hippo canines is in combat between bulls. Territorial fights involve both hippos opening their mouths wide, then clashing canines against each other in a series of powerful strikes. These fights can be prolonged and are often violent, with gaping wounds inflicted by the lower canines on the flanks, neck, and face of the rival.
Because the lower canines are the primary offensive weapon — long, heavy, and angled outward — fighting hippos aim specifically at each other’s flanks, where a deep slash from a lower canine can cause severe or fatal injury.
The wounds left on older bulls by decades of fighting are often extensive. Scarring around the neck, flanks, and snout of an adult male hippo is a reliable indicator of age and history. Bulls with heavy scarring are typically dominant animals that have fought and won repeatedly.
Defence Against Predators
When a hippo is threatened by a predator — or, more commonly, by a human — it uses the gape display first. If that fails, the bite follows. A single bite from an adult hippo is sufficient to kill or severely incapacitate virtually any terrestrial predator, including lions, hyenas, and crocodiles. Documented cases of hippos killing crocodiles with a single bite are not uncommon.
Infanticide
Adult bulls sometimes use their canines against calves — particularly young males — in acts of infanticide that eliminate future competition. This is one of the significant natural risks facing hippo calves in the first year of life.
Pygmy Hippo Teeth: Key Differences
The pygmy hippopotamus (Choeropsis liberiensis) has a notably different dental anatomy:
- 34 teeth (vs. 36 in common hippos)
- One pair of incisors (vs. two in common hippos)
- Much smaller canines: upper and lower canines reach only about 2–5 cm, compared to 30–50 cm in common hippos
- Jaw structure allows for some side-to-side movement, giving it slightly better grinding capacity
- Similar bite force to common hippos relative to body size
The reduced canine size in the pygmy hippo reflects its very different social structure: pygmy hippos are solitary rather than pod-living, and have much less frequent intraspecific combat than common hippos.
Frequently Asked Questions About Hippo Teeth
- How big are hippo teeth? The lower canine teeth (tusks) of a common hippo typically grow to 40–50 cm (16–20 inches). In exceptional individuals they can reach 71 cm (28 inches), and the longest ever recorded was 122 cm (48 inches). The incisors reach up to 40 cm.
- What is hippo bite force in PSI? The hippopotamus has a measured bite force of approximately 1,800 PSI (8,100 Newtons), recorded from a female by Dr. Brady Barr for National Geographic. Male bite force is believed to be higher but has not been directly measured.
- Are hippo teeth ivory? Yes. Hippo canine teeth and incisors are composed of ivory — a dense form of dentine. Hippo ivory is denser and whiter than elephant ivory and was widely traded historically. Trade in hippo ivory is now regulated under CITES.
- Do hippos use their teeth for eating? No. The large canines and incisors are weapons for fighting and threat display, not for processing food. Hippos eat using their wide muscular lips to grip grass, and their molars to chew it. The incisors actually prevent lateral jaw movement, making the hippo a less efficient chewer.
- How wide can a hippo open its mouth? A hippo can open its jaw 150 to 180 degrees, creating a gape of approximately 90 to 120 cm (3 to 4 feet) at full width. This is roughly four times the maximum jaw opening angle of a human.
- Why do hippos open their mouths wide? The wide-open mouth display — sometimes described as a “yawn” — is a warning behaviour. It exposes the canine teeth and communicates a threat to rivals or perceived dangers. It is typically the first stage of aggressive escalation, before vocalisation, mock charges, and a real charge.
- Do hippo teeth grow back? Hippo canines grow continuously throughout the animal’s life (they are hypselodont), meaning they do not stop growing and wear is compensated by continuous growth. They do not regrow from scratch if removed. The deciduous (baby) teeth of some individuals may be retained alongside permanent teeth.