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The Dichotomous Structure of Humpback Whale Song: Evidence for a Multi-message Mating Display

Centre for Marine Science and Technology Lunchbox Seminar

title

The Dichotomous Structure of Humpback Whale Song: Evidence for a Multi-message Mating Display

 

speaker

Dr. Anita Murray
 

date

Friday, 15 September 2017

time

12:00 to 1:00pm

location

Room 147
Building 301
Curtin University

abstract

 

Animals may produce a multi-message display with structurally distinct components that facilitate male-male interactions and female choice. The simple, stereotypic, lower frequency components generally convey group membership and function in mate attraction and/or mediate male-male interactions over large distances.

The complex, individually variable, higher frequency components generally function in courtship of nearby females. Humpback whale song is a male mating display with ‘units’ (or sounds) arranged into sequences called ‘phrases’. Singers repeat a particular phrase a variable number of times (called a ‘theme’) before switching to repetitions of a different phrase (i.e., a different theme). These phrases are grouped into ‘phrase types’, and each theme is differentiated by a characteristic phrase type. Variability among phrases of the same type can occur due to the imperfect repetition of phrases during a theme. These inexact repeats are referred to as ‘phrase variants’.

Behavioral studies support inter- and intra-sexual functions for song; therefore, song may be a multi-message display with two structurally distinct categories of phrase types, ‘simple’ and ‘complex’. To investigate this hypothesis, the songs of 17 east Australian whales (8 from 2004 and 9 from 2011) were analyzed. Self-organizing feature maps were used to determine unit types, and the Levenshtein distance between phrases determined phrase variants. Phrase types were initially identified as stereotypic or complex based on differences in repertoire size (numbers of unit types and phrase variants) and the proportions of phrase variants that were unique to an individual versus shared amongst males. The structural differences between phrase types were further investigated using two-state hidden Markov models that partitioned phrases into two categories, ‘simple’ and ‘complex’. Simple phrase types included phrase variants that were shared by multiple individuals, had a shorter phrase length, smaller number of unit types, narrower range of lower frequencies, and less variability than complex phrase types. Complex phrase types had a larger degree of structural variability and included phrase variants that were unique to an individual. The structural characteristics of simple phrase types were consistent with the mate attraction/male-male competition component of a multi-message display. Complex phrase types were structurally consistent with the courtship component.

These results provide structural support for the hypothesis that song is a multi-message display.

 

Linda Hunter

Administrative Assistant | Centre for Marine Science & Technology (CMST)

School of Science | Faculty of Science and Engineering

Curtin University
Office Tel | +61 8 9266 7380

Tel | +61 8 9266 4492

Email | CMSTAdmin@curtin.edu.au
Web | http://cmst.curtin.edu.au/

 

 

 

 

Curtin University

Fri 15 Sep 2017 To Fri 15 Sep 2017

12:00pm To 1:00pm