African bush elephants at Masai Mara National Reserve in Kenya

© Yva Momatiuk and John Eastcott/Minden Picture

Lunch buddies. African bush elephants

The social structure in elephant herds is surprisingly complex. All the adults in the herd exhibit what scientists call 'reciprocal altruism.' That is, an elephant will act in ways that give them no direct benefit – say, protecting or feeding a calf that isn't theirs. They do that because the other elephants in their herd will do the same for them.

The African bush elephant is the largest land mammal in the world and the largest of the three elephant species. Adults reach up to 24 feet in length and 13 feet in height and weigh up to 11 tons. As herbivores, they spend much of their days foraging and eating grass, leaves, bark, fruit, and a variety of foliage. They need to eat about 350 pounds of vegetation every day.