The active space of sperm whale codas: inter-click information for intra-unit communication

Ellen R. Jacobs*, Shane Gero, Chloe E. Malinka, Pernille H. Tønnesen, Kristian Beedholm, Stacy L. DeRuiter, Peter T. Madsen

*Corresponding author for this work

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaperJournal articleResearchpeer-review

Abstract

Sperm whales (Physeter macrocephalus) are social mega-predators who form stable matrilineal units that often associate within a larger vocal clan. Clan membership is defined by sharing a repertoire of coda types consisting of specific temporal spacings of multi-pulsed clicks. It has been hypothesized that codas communicate membership across socially segregated sympatric clans, but others propose that codas are primarily used for behavioral coordination and social cohesion within a closely spaced social unit. Here, we test these hypotheses by combining measures of ambient noise levels and coda click source levels with models of sound propagation to estimate the active space of coda communication. Coda clicks were localized off the island of Dominica with a four- or five-element 80 m vertical hydrophone array, allowing us to calculate the median RMS source levels of 1598 clicks from 444 codas to be 161 dB re. 1 μPa (IQR 153–167), placing codas among the most powerful communication sounds in toothed whales. However, together with measured ambient noise levels, these source levels lead to a median active space of coda communication of ∼4 km, reflecting the maximum footprint of a single foraging sperm whale unit. We conclude that while sperm whale codas may contain information about clan affiliation, their moderate active space shows that codas are not used for long range acoustic communication between units and clans, but likely serve to mediate social cohesion and behavioral transitions in intra-unit communication.

Original languageEnglish
Article numberjeb246442
JournalJournal of Experimental Biology
Volume227
Issue4
ISSN0022-0949
DOIs
Publication statusPublished - Feb 2024

Keywords

  • Active space
  • Behavioral ecology
  • Bioacoustics
  • Ecophysiology
  • Sperm whales

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