Final answer:
The apology shows that the animals' quarreling was futile and unproductive, similar to a dog endlessly chasing its own tail, which represents an action with no constructive outcome.
Step-by-step explanation:
The apology in the statement "the quarreling animals were united in only one respect: As a group, they were behaving like a dog chasing its own tail" illustrates that the animals' situation was futile and unproductive. This analogy conveys that the animals, despite their disputes, were acting collectively in a manner that is both pointless and endless, similar to a dog that chases its tail, going in circles without achieving anything meaningful. It indicates that their quarreling was not leading them anywhere and that their collective behavior did nothing to resolve their conflicts.