The passage has stated that meerkats exhibit altruism naturally as a group of them stands guard while the others hunt for food, risking their chances of getting any food that day. In fact, the sentinels would not stand there stomch-free. They ensure that they can sustain without food when they undertake the task by eating before it.
Moreover, the guarding meerkats tend to stand near the burrows so that they can escape fast from predators once they attack, of course after alarming the group. The fact that they alarm the others puts the group under the danger of baffling