Compilation of a call catalogue for Antarctic killer whales (Orcinus orca) Ecotype C.

Ilse.van.Opzeeland [ at ]


Killer whales (Orcinus orca) are highly social top predators occupying key ecological niches and are distributed throughout all world’s oceans. Killer whales are divided into nine to ten different killer whale ecotypes. Five ecotypes are exclusively present in the Northern Hemisphere and four to five exclusively present in the Southern Hemisphere. In contrast to the relatively extensively studied Northern Hemisphere ecotypes, only little is known on the distribution, abundance and social structures of the Southern Hemisphere killer whale ecotypes. Killer whale ecotypes mainly differ in color pattern, size and diet. The fish-eating Antarctic Ecotype C killer whales occur in regions with dense pack ice, where investigation of these animals is restricted to a minimum due to limited accessibility of these areas as a result of the prevailing ice and weather conditions. The study of Antarctic Ecotype C killer whales through passive acoustic monitoring (PAM) by contrast is much more effective as recordings can be made year round. Information on the vocal repertoire of specific killer whale ecotypes allows using passive acoustic recordings to derive information on type-specific abundance and distribution. Compilation of information on ecotype-specific vocal repertoire, however first requires visual confirmation of the vocalizing ecotype. On two occasions in February 2013, it was possible to collect concurrent visual and acoustic information on killer whales that occurred off the Antarctic continent. Here, I compile a call type catalogue for Ecotype C killer whales based on these two encounters. The analysed recordings contained 2276 examined calls, which were classified into 46 discrete call types. The absolute frequencies of occurrence of these call types ranged from 1 to 708 calls per call type. Most call types were composed of more than one segment. 50 % of all call types were monophonic and 45,7% were biphonic (i.e., consisted of two independent, in this case overlapping, fundamental frequencies in the call spectrum). 69,6 % of all call types start with a short and broadband pulse. The variability within call types was relatively high which complicated the classification of call types with the described method and resulted in an accordance of 45 % when the classification was cross-checked with a second independent observer. I suggest a number of alternative manual classification methods and evaluate how computer-based methods could contribute to develop a reproducible classification of killer whale call types.

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Schall, E. (2013): Compilation of a call catalogue for Antarctic killer whales (Orcinus orca) Ecotype C. , Bachelor thesis, Bremen University.

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