["Mind &Language, Volume 41, Issue 1, Page 21-50, February 2026. ", "\nWhile recent “animal linguistics” treats call form as arbitrary, various results suggest that some animals use a biological code to understand the calls of unrelated/unfamiliar species. To clarify matters, we distinguish among three degrees of interspecies comprehension. In the first (“Understand thy neighbor”), a species understands the calls of a neighboring species through exposure. In the second (“call convergence”), it understands the calls of an unrelated/unfamiliar species through evolutionary convergence and resemblance to familiar calls. In the third degree (“featural interpretation”), it uses a rule associating a meaning to a specific acoustic feature—hence a new road to (featural) compositionality.\n"]