What are the categories of Bigg's killer whale signals preferred by Orcasound, HALLO, and collaborators?

[scottveirs]

One approach to building a first catalog of Bigg's calls for Orcasound would be to use Orcasound recordings to create our own nomenclature. A more a collaborative approach (we prefer) is to stand on the shoulders of those who have already categorized the calls of Bigg's orcas.

Ideas:

1. Use the categories from the F. Thomsen recordings that John Ford contributed to the Orcasound archive: T01, T03, T07, T08.
2. Use the categories defined by Volker Deecke in his 2003 thesis and contextualize them with more recent correspondence with him:

Here are some helpful notes from Volker Deecke shared with me by Amalis Riera from their email correspondence in Februrary , 2021, thanks to an e-introduction from James PIlkington.

The two-voiced “loud” calls of the transients (WCT03, WCT04, WCT07, WCT12) are indeed tricky and have aspects of a graded continuum rather than discreet call types. WCT08 on the other hand is functionally and structurally more distinct and should be recognisable. 

We use “two-voiced” for any call that has an upper frequency component in addition to the lower frequency component.  Other researchers use “bi/monophonic”, but I believe “two/single-voiced” are the appropriate terms, since two independent sound producing structures are at work (see Wilden et al. 1998). There is good evidence that the two-voiced and single-voiced calls of killer whales are functionally distinct (e.g., Filatova et al. 2009), presumably because two-voiced calls give much more precise information on caller orientation (Miller et al. 2002, 2004).

This is strikingly obvious in transient killer whales, since the typical within-group communication after a kill only includes single-voiced calls (WCT01, WCT02, WCT08, WCT11 in BC/Alaska) whereas the two-voiced call types are reserved for contact-calling contexts (where individuals/groups are communicating/attempting to communicate with other distant groups), along with single-voiced call types. The WCT08 call type lacks an upper frequency component and is consistent with this pattern. That’s why I have always considered it separate from the “loud calls” (WCT03, WCT04, WCT07, WCT12). 

My doctoral thesis (see PDF link below) which includes a detailed categorisation of transient call types in Appendix III (you have probably seen this already…). I could try to dig out the corresponding sound files (but that might take a while). 

In many WCT03/WCT13 calls, the upper frequency starts quite some time before the lower frequency component and I can see how these might be mistaken for WCT08s. However, WCT08 has a distinct buzz at the start. 

I wouldn’t consider WCT08 to be two-voiced since it doesn’t have an overlapping upper frequency component (and this is consistent with its frequent use in within-group communication contexts). There is a rather pronounced jump in frequency of the  lower frequency component  between part 1 (the buzz) and part 2 (and then down again in part 3). 

WCT13 (not a call type I/John were entirely happy with as my automated categorisation seemed to treat it as a bit of a rubbish bin for aberrant or variable calls.)

In his thesis, Deecke (2003) wrote: Wherever call types are largely consistent with those of Ford (1984) and Ford & Morton (1991), their original numbers are retained.