Sanvito,S. & Galimberti,F.  2000. Bioacoustics of southern elephant
seals. II. Individual and geographical variation in male aggressive
vocalizations. Bioacoustics. 11: 287-307.

Abstract
In traditional studies of animal communication individual variability
was sometimes considered less relevant than species specific aspects,
mostly because the goal was the classifications of sounds in
repertories. On the other side, individual variability seems to have a
significant role in signal function and evolution. In this paper, we
analyze individual variation of structure of aggressive vocalizations of
male southern elephant seals, and we compare sounds from our main study
population, Sea Lion Island (Falkland Islands), with sounds recorded in
the nearby population of the Valdes Peninsula (Patagonia, Argentina). We
firstly analyzed repeatability of acoustic parameters at vocalization
and male level. Repeatability of bouts of the same vocalization was
extremely high, and this confirmed that vocalization is the fundamental
level of organization of male acoustic communication in this species.
Also repeatability of vocalizations of individual males was very high,
and hence sounds may effectively convey information about identity of
the individual who emits the sound. Male aggressive vocalizations were
classified in a small number of types, and each male emitted always the
same type of vocalization. We compared the typology of sounds emitted by
Sea Lion Island males with vocalizations by Valdes Peninsula males, and
we found striking differences. None of the sound types was shared by the
two populations, and, although similar in fundamental acoustics, sounds
from the two populations had different macrostructure. We conclude that
these two populations present dialects in male acoustic communication,
although scarcity of recordings from other populations limit the scope
of this conclusion.