Call repertoire of infant African elephants: first insights into the early vocal ontogeny.

African savannah elephants (Loxodonta africana) have a complex acoustic communication system, but very little is known about their vocal ontogeny. A first approach in ontogenetic studies is to define the call repertoire of specific age groups. Twelve hundred calls of 11 infant elephants from neonatal to 18 months of age recorded at the Vienna Zoo in Austria and at the Daphne Sheldrick's orphanage at the Nairobi National Park, Kenya were analyzed. Six call types were structurally distinguished: the rumble, the bark, the grunt, the roar (subdivided into a noisy-, tonal-, and mixed-roar), the snort, and the trumpet. Generally, within-call-type variation was high in all individuals. In contrast to adult elephants, the infants showed no gender-dependent variation in the structure or in the number of call types produced. Male infants, however, were more vocally adamant in their suckle behavior than females. These results give a first insight to the early vocal ontogeny and should promote further ontogenetic studies on elephants. Due to their vocal learning ability in combination with the complex fission-fusion society, elephants could be an interesting model to study the role of imitation in the vocal ontogeny of a nonprimate terrestrial mammal.