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Abstract
The evolutionary origin of rhythm perception, a cognitive ability essential to musicality,
remains unresolved [1-5]. The ability to perceive and memorize rhythmic sounds is
widely shared among humans [6] but seems rare among other mammals [7, 8]. Although
the perception of temporal metrical patterns has been found in a few species, this
ability has only been demonstrated through behavioral training [9] (but see [10] for
an example of spontaneous tempo coordination in a bonobo), and there is no experimental
evidence to indicate its biological function. Furthermore, there is no example of
a non-human mammal able to remember and recognize auditory rhythmic patterns among
a wide range of tempi. In the northern elephant seal Mirounga angustirostris, the
calls of mature males comprise a rhythmic series of pulses, with the call of each
individual characterized by its tempo and timbre; these individual vocal signatures
are stable over years and across contexts [11]. Here, we report that northern elephant
seal males routinely memorize and recognize the unique tempo and timbre of their rivals'
voices and use this rhythmic information to individually identify competitors, which
facilitates navigation within the social network of the rookery. By performing playbacks
with natural and modified vocalizations, we show that males are sensitive to call
rhythm disruption independently of modification of spectral features and that they
use both temporal and spectral cues to identify familiar rivals. While spectral features
of calls typically encode individual identity in mammalian vocalizations [12], this
is the first example of this phenomenon involving sound rhythm.