DOI 10.1007/s10071-009-0298-9ORIGINAL PAPER Mother–Calf vocal communication in Atlantic walrus:

• Main Authors: Anim Cogn, Isabelle Charrier, Thierry Aubin, Nicolas Mathevon
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Odobenus rosmarus; walrus*
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.613.4359; http://www.cb.u-psud.fr/pdf/Charrier_etal_AnimCogn_2009.pdf

Abstract In all colonial pinnipeds studied, mother–young vocal recognition exists and allows rapid and reliable meet-ings in spite of the confusing environment of the breeding colony. The eYciency 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 gregari-ous 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 artiWcial neural network analyses resulted in high correct classiWcation rates, underlying a well-deWned individual stereotypy in parame-ters 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 modula-tion and frequency spectrum being highly resistant to degra-dation during propagation. Thus, acoustic analysis and propagation experiments suggest that these frequency parameters might be the key acoustic features involved in the individual identiWcation process. This experimental study clearly demonstrates that Atlantic walrus has devel-oped a highly reliable mother–calf vocal communication allowing such strong social bond.