She and other zoo visitors watched with abated breath, thinking that the hippo would shut its mouth any minute and snap off the zebra's head. However, soon it was obvious that the zebra was actually there at the invitation of the hippo and it appeared to be cleaning its teeth!
The process lasted for fifteen whole minutes, allowing for plenty of photo opportunities, before the zebra calmly walked off to continue with its day . . . . possibly another teeth appointment?
The visitors at the Zoo were a little surprised at the Hippo's calm behavior because this short and stout mammal is considered to be the world's most aggressive creature and often regarded as the most ferocious animal in Africa.
However, while that is true, Hippos are lazy animals who lounge in the water all day, emerging only at night to feed on the short grasses and any other low lying plants and fruits they may find. These herbivores attack only when they feel threatened. In the wild, they are known to aggressively go after two enemies - crocodiles who share their rivers and human beings, probably because of past bad experiences!
sources:bbcnews.com, dailymail.co.uk, wikipedia.org