Why Are Hippos So Dangerous? Facts About Hippo Attacks

Why do hippos attack people?

Hippos do not hunt people. They are herbivores that graze on grass at night, and almost every attack is defensive. Three situations cause most trouble.

Territorial bulls in the water. Dominant males hold stretches of river or lakeshore, usually about 50–100 m (160–330 ft) of riverbank or 250–500 m (820–1,640 ft) of lakeshore. A bull treats intruders, including canoes and small boats, as a challenge. A boat that bumps or passes over a submerged hippo can be lifted, bitten or overturned.

Mothers with calves. Hippo cows are fiercely protective. A mother may attack anything she sees as a threat to her young, and the risk is highest near calving areas in shallow water.

Hippos cut off from water. At night hippos walk inland to graze, sometimes several kilometers. A hippo that feels its route back to the water is blocked by a person, a vehicle or a fence may charge straight through whatever is in the way. Many attacks on land happen at dusk or after dark, when people walking near rivers do not see a grazing hippo until they are close.

What makes a hippo attack so serious?

Several features combine to make a hippo one of the most powerful animals a person can meet:

Hippos also give little warning by human standards. The open-mouthed “yawn”, loud grunts and splashing are warning signs, but a frightened or cornered hippo may charge almost at once.

How many people do hippos kill?

The honest answer is that nobody knows precisely. A figure of around 500 deaths a year in Africa appears in many articles and documentaries, but it is not based on a published, continent-wide survey. Attacks happen across dozens of countries, often in remote fishing villages, and many are recorded only locally or not at all.

What is clear is that hippos cause regular deaths and injuries wherever people fish, wash, fetch water or farm along hippo rivers. Single incidents can be serious: in 2014, for example, a hippo overturned a boat on the Niger River in Niger, and about a dozen people drowned. Hippos are therefore often listed with Nile crocodiles as among the most dangerous large wild animals to people in Africa, while lions, despite their reputation, cause fewer deaths in most regions. The Nile crocodile shares many of the same rivers, which adds to the risk for people on the water.

Why are hippos more aggressive than other big herbivores?

Biologists point to the hippo’s way of life. Hippos crowd into limited water during the day, so space is precious, and dominant bulls gain mating access by holding the best stretches. That rewards aggression. Fighting between bulls is common and can leave deep scars or kill the loser.

Their size and tusks also mean adult hippos have few predators, so they tend to stand their ground rather than flee. Combined with poor visibility in muddy water and frequent contact with people at riverbanks, conflict is almost inevitable. Similar defensive behavior makes other big African herbivores risky too; see Why are Cape buffalo so dangerous?

Where are hippo attacks most common?

Most incidents happen where people depend directly on rivers and lakes. Fishers in dugout canoes, people crossing rivers, and villagers collecting water or washing at the shore are most exposed. Conflict also rises where farms reach the water’s edge, because hippos graze in crop fields at night and farmers may try to chase them off.

Droughts make things worse. As pools shrink, hippos crowd together, food runs short and animals become more stressed and more likely to travel far from water, into farmland and villages. In Colombia, introduced hippos descended from animals kept by Pablo Escobar have also raised concerns about safety for people living along the Magdalena River.

How do people stay safe around hippos?

Visitors on safari are at low risk when they follow park rules and guides’ instructions. The basic advice is about distance and respect:

• Stay in vehicles or behind barriers at viewpoints, and never walk near rivers or lakes at dusk or at night in hippo areas.
• Never get between a hippo and the water.
• On boat trips, go with experienced local guides who know where hippos rest, and keep well away from pods.
• Treat an open mouth, head-shaking, grunting or splashing as a warning to back away slowly.

If anyone is injured by a hippo, seek emergency medical help immediately. In the US call 911, in the EU call 112 and in the UK call 999; in other countries, contact local emergency services or your guide’s emergency contacts.

Are hippos dangerous in zoos?

Zoo hippos are still strong and potentially dangerous, which is why keepers work with them from behind barriers and modern exhibits separate visitors with thick glass and moats. Seeing hippos this way, especially in underwater viewing areas, is one of the safest ways to watch their behavior up close.