Mother-Calf Vocal Communication in Atlantic walrus (Igloolik, NU, Canada)

Atlantic walrus Mothers and Calves' vocalisations were recorded in natural context in 2006 and 2008 in the Foxe Basin, Igloolik, Nunavut, Canada.

In total, 544 barks from 22 calves and 164 barks from 11 females have been recorded and analysed. Further vocalisations produced by adults have also been recorded in different social contexts as well as some underwater vocalisations. In addition to these recordings, playback tests on females were performed to assess calf's vocal recognition, and propagation tests of calls over water and ice surface have been carried out to assess the efficiency of vocal communication in their natural environment.

These data have been submitted to publication, the abstract is copied below:

In all colonial pinnipeds studied, mother-young vocal recognition exists and allows rapid and reliable meetings in spite of the confusing environment of the breeding colony. The efficiency of this recognition process guarantees pup survival, especially in species where females alternate foraging sea trips and lactation periods on land. The Atlantic Walrus (Odobenus rosmarus rosmarus) is a highly gregarious pinniped with females attending their calves for an extended period of time (2-3 years). Although we expect mother-calf vocal recognition to occur in this species due to the high density of individuals packed in herds, it has never been experimentally demonstrated. Here, we assessed the individual stereotypy of both mother and calf barks recorded in the wild by measuring frequency and temporal acoustic parameters. Both discriminant function and artificial neural network analyses resulted in high correct classification rates, underlying a well-defined individual stereotypy in parameters related to frequency modulation and frequency values. Playback experiments showed that mothers were more responsive to the barks of their own calf than to those of unrelated young. Finally, propagation experiments revealed that barks propagate at greater distances over water surface than over ice, acoustic features such as frequency modulation and frequency spectrum being highly resistant to degradation during propagation. Thus, acoustic analysis and propagation experiments suggest that these frequency parameters might be the key acoustic features involved in the individual identification process. This experimental study clearly demonstrates that Atlantic walrus has developed a highly reliable mother-calf vocal communication allowing such strong social bond.