In evolutionary biology, reciprocal altruism is a behaviour whereby an organism acts in a manner that temporarily reduces its fitness while increasing another organism's fitness, with the expectation that the other organism will act in a similar manner at a later time.
Cleaning symbiosis: a small cleaner wrasse (Labroides dimidiatus) with advertising coloration services a big eye squirrelfish (Priacanthus hamrur) in an apparent example of reciprocal altruism.
Eurasian jay, Garrulus glandarius, gives loud alarm calls from its tree perch when it sees a predator.
Arctic terns protect their offspring extremely aggressively by very quick drop-downs from a stationary flight over their enemies. Other birds often benefit from this behavior by breeding very close to the Arctic terns.
Altruism is the principle and practice of concern for the well-being and/or happiness of other humans or animals above oneself. While objects of altruistic concern vary, it is an important moral value in many cultures and religions. It may be considered a synonym of selflessness, the opposite of selfishness.
Giving alms to the poor is often considered an altruistic action.
Giving alms to beggar children
Volunteers assist Hurricane victims at the Houston Astrodome, following Hurricane Katrina.
Helping the homeless in New York City