Figure 1.

Different forms of vocal production learning. Vocal production learning is not a dichotomous trait but arranged on a continuum [13]. Manifestations of vocal production learning range from subtle modifications of existing call or song types to the imitation of vocalizations of other species or novel sounds. Sketches provide graphic references to mammalian vocal production learners covered in our review, and their position on the continuum represents our evaluation of their vocal production learning abilities. Three domains of vocal production learning (respiratory, phonatory and filter learning), their association with the sound producing apparatus, and the resulting signal characteristics are depicted as well. Most of the examples covered in our review concern phonatory learning. Note that different mammals can have vastly different sound production mechanisms (the human apparatus serves as a familiar example). Figure modified with permission from Scharff et al. [14]. (Online version in colour.)