午餐伙伴(Lunch buddies)

大象群的社会结构异常复杂。群中所有的成年大象都表现出科学家所说的“互惠利他主义”。也就是说，大象的行为方式不会给它们带来任何直接好处——比如保护或喂养一头不是它们的小牛。他们这样做是因为他们群中的其他大象也会这样做。
原文：
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.
《© Yva Momatiuk and John Eastcott/Minden Pictures》