Vocal Learning in Southern Elephant Seals S. Sanvito 1,2, F. Galimberti 1, E.H. Miller 2 1 Elephant Seal Research Group 2 Memorial University of Newfoundland

Agonistic vocalizations Vocalizations are present in about 70% of agonistic interactions between males Vocalizations settle about 50% of agonistic interactions

Acoustics of agonistic vocalizations Pulse trains High sound level (up to 120 dB) Low frequency (dominant frequency around 250 Hz) Each call made of different “syllables” Syllables structure is independent from the frequency structure of the vocalization

This study Young males vocalizations are variable, mature males vocalizations are fixed Fixed vocalizations can be classified in vocal types shared by two or more males Changes in the distribution of vocal types in consecutive years are much compatible with vocal learning Alternative explanations are unlikely

Methods: general Small and localized population Sea Lion Island, Falkland Islands 8 breeding seasons September to December Individual recognition of males Tags and dye marks

Methods: acoustics Recording of vocalizations (standard solicitation) vocalizations from 284 males (3 to 16 years old) - Some males recorded in more than one breeding season (1-6) - 29 males followed throughout their entire vocal development Classification in vocal types by visual inspection of waveforms - Temporal patterning of syllables 23 acoustic variables used to validate the visual classification - Time - Intensity - Frequency

Variable vs fixed vocalizations Young males have variable vocalizations i.e., the syllables pattern varies in different calls Mature males have fixed vocalizations i.e., each male emits always the same syllables pattern Percentage of males with variable vocalizations decreases with age Vocalizations of mature males have a high repeatability of syllable features (mean = 0.84)

Vocal types: description Some males share the same syllables pattern Some males show a unique (not shared) syllables pattern Males which share the same syllables pattern are classified in the same vocal type 6 vocal types recognized in this study

Vocal types: validation Reliability of visual classification in a blind test = 100% Significant differences in acoustics of vocal types (non parametric MANOVA: p = ) Good results in classification by canonical discriminant function (mean = 82.1% correct)

Acoustic environment Young males listen to vocalizations of mature males mainly (or only) during the breeding season Harem holders vocalizations are the main component of acoustic habitat of young males: - Holders settle contest with peripheral males using vocalizations in 56% of cases - In 76.2% of the interactions in which a vocal component is present, a harem holder is vocalizing - In the interactions involving a harem holding male, it vocalizes in 75.5% of cases Large harems have more associated (often young) peripheral males (rho = 0.729, n = 68 harems)

General hypothesis Young males imitate harem holders vocal type The distribution of vocal types in the population depends on the survival and breeding status of mature males

Changes in vocal types frequencies Frequencies of vocal types were not homogeneous among years (  2 = 184.2; p 10k = ) Only 2 vocal types, out of 6, were present in the first year of study

Original vocal types Vocal type D: bell shaped trend, it was the most common Original vocal types expected to be at some point of the increasing/decreasing trend Vocal type C: decreasing trend, almost disappeared

Spread of new vocal types 56 males showed a fixed unique vocalization 4 of them became holders of large harems, with many peripherals These 4 males started 4 new vocal types which spread in the population, showing an increasing trend None of the unique vocalization of the remaining 52 males spread in the population

Problems and drawbacks Observational only, no playback: longitudinal data Alternatives: - inheritance of vocal types ? - repeated immigration of males sharing a new vocal type ? Origin of new unique vocalizations ?

Conclusions Presence of vocal types Variation of vocal types distribution compatible with vocal learning Why do young males come to land during the breeding ? Acquisition of vocal competence

Thanks to the seals and to the many people that helped during the years of field work at Sea Lion Island. Funding provided by Lerner-Gray Foundation, the University of Milano and the Italian National Council for Scientific Research.