• James D. Darling,

    1. West Coast Whale Research Foundation, 1200-925 West Georgia Street, Vancouver, British Columbia V6R 2L3, Canada E-mail:
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  • Martine Bérubé

    1. School of Biological Sciences, University of Wales, Deinol Road, Bangor, Gwynedd LL57 2UW, Wales, UK and Department of Ecosystem Sciences, Policy and Management, Division of Ecosystem Sciences, University of California Berkeley, 151 Hilgard Hall #310, Berkeley, California, U. S. A.
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Two non-mutually exclusive hypotheses on the function of the humpback whale song are: (1) it attracts females to the male singer; (2) it is a male-male display, that may order status. To evaluate these, from 24 January-13 April 1997 off Maui, Hawaii, 42 singers were located, audio-recorded, photo-identified and monitored for interactions with other whales. Whales that joined singers were biopsy sampled for molecular determination of sex. In 76% (32 of 42) of the interactions, a lone non-singing adult joined the singer. In the remainder, singers stopped singing and joined a nearby group or accompanied other whales. In 81% (26 of 32) instances where a lone adult joined a singer, the pair split again within minutes; otherwise a group formed. In one such group the pair became a trio and eventually joined a competitive group. Behavior in joining/splitting interactions ranged from a single pass-by, to surface activity such as tail lobs and breaches. The sex of 22 joiners was determined: 14 genetically and eight behaviorally. All were males. Humpback whale song preceded, and at times followed, male-male interactions of variable duration and agonistic level in and around the breeding season. If considered within the context of a proposed dominance polygyny mating system, these observations appear to support speculation that the song may function in male social ordering.