Correlates of variability in killer whale stereotyped call repertoires.
Killer whales vocalisations include repertoires of stereotyped call types (Ford 1984). There is strong evidence that these vocalisations are learnt (Hoelzel and Osborne 1986; Bain 1989; Deecke et al. 2000; Yurk et al. 2002). Call types can be group specific or shared amongst a number of groups, depe...
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| Format: | Thesis |
| Language: | unknown |
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2005
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| Online Access: | http://etheses.dur.ac.uk/2913/ http://etheses.dur.ac.uk/2913/1/2913_743.pdf |
| Summary: | Killer whales vocalisations include repertoires of stereotyped call types (Ford 1984). There is strong evidence that these vocalisations are learnt (Hoelzel and Osborne 1986; Bain 1989; Deecke et al. 2000; Yurk et al. 2002). Call types can be group specific or shared amongst a number of groups, depending upon the social structure of the population or the call type (Ford 1991; Deecke 2003). It is thought that these call types function in the group cohesion and coordination (Hoelzel and Osborne 1986; Ford 1989 1991; Miller 2000, 2002). Some call types contain two overlapping, independently modulated, components each having different transmission properties (Miller 2002), these call types have a higher estimated active space than single- component call types (Miller 2006).This thesis investigates the evolution of these call type repertoires, focusing on call type usage and structure of the Southern Resident population over a period of 27 years, but including comparisons with other populations. I present evidence of hetero-specific mimicry and further evidence for vocal production and usage learning in killer whales. I compared the relative frequency of use of call types between two time periods (1977-81 & 2001-2003) and between contexts, such as direction changes with directional travel and multi-pod aggregations with single pods. I found a strong correlation of relative call type usage for each pod between the two time periods and each pod was easily acoustically distinguishable from the other two pods in both periods. The implications of these results for a role of call type repertoires in kin recognition are discussed. The least cohesive pod produced a significantly higher proportion of two-component call types than the other two more cohesive pods. Lone whales separated from their pod also used a rare subset of two-component call types rather than their pod's main call types. In recordings of multi-pod aggregations I recorded a high proportion of the same subset of two-component call types not commonly ... |
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