Hippopotamus oral care training
June 30, 2026
Currently, Ueno Zoo keeps one Hippopotamus.
Hippopotamus are prone to oral health problems and require regular care. Ueno Zoo also implements oral care using "Eurasian Moorhen training" as part of its health management program.
Eurasian Moorhen training is a method of training aimed at ensuring the healthy care of animals and the safe working conditions of humans. It involves repeatedly teaching animals that "good things happen when they behave in the way animal keeper want," ultimately enabling them to spontaneously follow animal keeper' instructions.
This time, we'll explain in detail how to train Hippopotamus to open its mouth and brush its teeth in order to perform oral care.
This training requires two or more people, as one person will be responsible for giving instructions and rewards, while the other will be responsible for brushing the teeth.
First, the person in charge of giving instructions and rewards uses a tool called a "target," which is a stick with a marker on the end, to give instructions to Hippopotamus and guide it to a position where it can easily brush its teeth.
When Hippopotamus exhibits desirable behavior, it is rewarded by having water flow from a hose into its mouth.
Hippopotamus will then open its mouth wide and continue to receive the water, seemingly enjoying it. In the meantime, the person in charge of brushing its teeth can use a brush to clean its teeth.
For toothbrushes, we use natural materials, specifically bamboo bristles attached to a bamboo stick.
This is to minimize the impact on the Hippopotamus 's body in the unlikely event that it closes its mouth and swallows the brush.
Furthermore, by attaching the brush to a bamboo stick, a safe distance is maintained between Hippopotamus and the person brushing its teeth, ensuring that fingers do not get caught even if the hippo closes its mouth during brushing.
The photos below show the inside of an animal's mouth immediately after eating and after brushing its teeth. Please pay attention to the gaps between the teeth. Immediately after eating, there was hay stuck between the teeth and gums, but you can see that it has been completely removed after brushing.
In this way, training allows you to brush your teeth properly and keep your mouth clean.
Furthermore, because they open their mouths wide, we can directly check for problems such as canker sores, which is very helpful for managing their health.
We will continue training, constantly innovating to ensure that both Hippopotamus and animal keeper can safely manage their health.
[Ueno Zoo West Garden Animal Care and Exhibition Staff]