Hippopotamus Yawning at Sunset, Olare Orok River, Maasai Mara National Reserve, Kenya

A hippopotamus (Hippopotamus amphibius) opens its mouth wide as it yawns with the golden light of sunset reflecting on the Olare Orok River in the Maasai Mara National Reserve in Kenya. In hippopotamuses, yawning is a sign of aggression, allowing them to show off their long, sharp teeth. The hippopotamus can also open its jaws up to 180°, which is the widest opening of any land animal.