How many hours per day, on average, do elephants sleep?
Wild elephants sleep an average of only two hours a night, making them one of the lightest sleepers among mammals. It isn’t possible to record the electrical brain activity of an elephant because of the thickness of their skulls. To study elephant sleep habits, researchers attached motion sensors to the elephants’ trunks. As one of the most active part of the elephant’s body, the trunk is usually idle only while the animal is sleeping. Source: NewScientist.com
and the order Proboscidea. Three species are currently recognized: the African bush elephant, the African forest elephant, and the Asian elephant.