only parrots (
6) and dolphins (
7) have been found capable of using arbitrary, learned signals to label objects in experimental studies. For both groups there are data that suggest this ability is also present in their natural communication system (
8⇓⇓⇓–
12). Thus, both dolphins and parrots present interesting avenues of research for understanding labeling or naming in the animal kingdom.
Bottlenose dolphins are particularly interesting in this respect because they develop individually distinctive signature signals, termed “signature whistles” (
13⇓–
15). A signature whistle is a learned, individually distinctive whistle type in a dolphin’s repertoire that broadcasts the identity of the whistle owner
