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.
Conclusion
The sentinel's behavior is not entirely self-interested / it's at least somewhat altruistic.
Evidence
Even though the sentinel gets killed by predators less often than the foragers do, the sentinel's loud bark alerts the foraging meerkats to the presence of danger.
Evaluate
The author is concluding that the sentinel is acting at least somewhat altruistically because its bark warns the other meerkats of danger.
If we were trying to argue the anti-conclusion (that the sentinel's behavior is entirely self-interested, not altruistic), then how would we explain the barking?
Well, maybe the sentinel just starts barking because he's freaked-out by seeing a predator. The stimulus says the loud bark is emitted as the sentinel dashes for cover. So it's not like the sentinel runs back to the others and says, . It's more like the sentinel gets freaked out, yells "Aaaaaaahhhh!", and dives for cover.
Meanwhile, the foraging meerkats hear the yelp of terror and think, "Eddie's scared -- there must be a predator."
Goal
This seems to test a distinction LSAT goes back to a lot (in the top 15, but not top 10 of famous flaws) between Intent vs. Result
The barking Results in a beneficial warning to the other meerkats, but the author is acting like we know that the Intent of the barking was to benefit others; it's possible the barking was just an expression of sheer terror.
Accordingly, an answer might describe this with Causal flaw language, since the author is concluding one causal interpretation for the barking (trying to warn others) when other possible interpretations are available (involuntary sounds of terror).