Sounds like the news reporter is drawing his own conclusions based off the study. Most scientists are very careful with the words they use to describe things.
The reason why they leave the colony is because they sense death is imminent.
This looks like the only thing that can really be taken home from the article.
Explaining the low level motivations for choosing to die outside of the hive is another matter entirely.
It seems like altruism results from and artificial increase of Utility stemming from irrational factors. Let see 2 examples:
1) A is obsessively in love with B
2) B's utility for A is 0.
3) A's utility for A is 10.
4) A's utility for B is 11 due to #1.
5) A would sacrifice A to save B because 11 > 10.
Is #5 altruistic? Its based on a very irrational premise, so probably.
1.) A's utility for A is 10
2.) A's utility for social group H is 10
3.) A will explode in the near future no matter what happens
4.) A's utility for A is now 0 due to #3
5.) A will move away from H since 10 > 0
Altruistic? Not so much.
Is irrational behaviour actually rational behaviour masked by complicated social, environmental and temporal contexts? Are emotions the result of an individual's adaptations for operating in various intersecting social networks? Fear and Anger helps one operate within the network of predators and prey in ones surrounding environment, so its not surprising that most animals can display these emotions. The types of emotions an intelligent agent can display must be related to the complexity of its social networks.
In the end, the ant probably doesn't need any emotional or altruistic tendencies to make the rational decision to save the hive. Without the hive the ant is as good as dead, so at worst, it must have the same utility value as its own sense of self preservation. If the ant knows its going to die from something, its rational to die alone to prevent contamination of the hive.