One meerkat stands guard so the rest of the mob can keep eating

While a meerkat group forages, one member typically climbs onto a termite mound or bush to watch for eagles and jackals, barking a specific alarm call for each type of threat so the others know whether to run or hide. Sentinels take turns and get no obvious bonus for the risk, making the behavior a long-running test case for how cooperation evolves among animals that aren't even close kin.

— Tim Clutton-Brock et al., Sentinel Behaviour in Meerkats, Suricata suricatta — Animal Behaviour, 1999