SRKW Click Catalog

orca near seattle in the surface — A Southern Resident killer whale surfaces for air in the Salish Sea.

Version 1 Created by Max Bolen, 2024:

Orcas (Orcinus orca) are highly social, vocal animals that produce an array of vocalizations; calls, whistles, clicks, and percussives. Their various calls and whistles have been documented, categorized, cataloged, and researched over many years. However, not a lot of research has been put into their echolocation clicks which they use to forage and navigate around their ecosystem. Unlike calls and whistles, clicks do not have a distinct pitch or horizontal structure in a spectrogram, which makes possibly unique clicks hard to identify. Since research in this field is still relatively young, we do not know if individual clicks are unique by themselves, but what we can observe is distinct inter-click intervals (ICIs) in a sequence of clicks that differentiate the speed of clicks.

This project started to advance research into orca clicks and provide the Orcasound community with a publicly accessible catalog showcasing the variety of clicks produced by our local Southern Resident killer whales (SRKWs), captured through our live hydrophones. Recognizing that the scientific understanding of orca clicks is still developing, I propose these SRKW click sequence categories for educating listeners, and for beginning to establish a labeling standard for future annotations. In addition, I have prepared improved click recordings for the Orcasound learn page and created a more user-friendly catalog for listeners. Ultimately, I wanted to provide a foundation for those interested to begin their learning and inspire their own investigations into orca echolocation.

This catalog was developed with recordings from Bush Point and the Orcasound Lab during the 2020 to 2024 seasons. Max decided upon 5 ranges of clicks classified by their ICIs and 2 special cases heard in our local study areas to provide you with a simple guide to analyzing and appreciating SRKW clicks as you hear them. The ICI ranges are: very fast (<50ms), fast (50-100ms), medium (100-250ms), slow (250-400ms), and very slow (>400ms). The first special case is the buzz: such rapid clicks that they sound like one continuous buzz. The second special case is a sweep, in which the click amplitude increases and decreases – likely caused by an orca sweeping their head towards and away from the hydrophone while echolocating. This will allow you to confidently and consistently annotate the live audio stream when you hear clicks and help Orcasound learn more about the intricacies of orca echolocation in the Salish Sea!