In groups of meerkats, for example, some mebers supposedly risk their lives to ensure other members' survival. In this case, sentinels (members who risk themselves) stand guard and alert the other meerkats by producing and alarm in case there are predators nearby. In the past, scientists believed that these altruistic members standed guard with an empty stomach. What new studies found, according to the professor, is that such sentinels would eat before they went stand guard, so they are not sacrificing their own chances to gain calories before accomplishing