Meerkat sentinels,  so-called because they watch for predators while other meerkat group members forage, almost never fall victim to those predators, yet the foragers often do  This advantage accruing to the sentinel does not mean that its watchful behavior is entirely self-interested  On the contrary, the sentinel' s behavior is an example of animal behavior motivated at least in part by altruism
The loud bark emitted by the sentinel as it dashes for the cover of the nearest hole alerts other group members to the presence of danger
inferring solely from an effect produced by an action that a purpose of the action is to produce that effect