Listening to the Past

…but first a name

This is what we see when we study humpback whales... but what do we hear?

This is what we see when we study humpback whales… but what do we hear?

I’ve dedicated the past 3 years to understanding non-song vocalizations, which admittedly is just a drop in the bucket. Now, as I venture into my fourth year of this relationship I have to acknowledge that I’ve moved from one chapter of my research into another. The Rapunzel Project (the whimsical name for my M.S. project) was my first foray into bio-acoustics, large scale fieldwork, and in internship development. While I wouldn’t consider myself an expert at any of these things, I’m also no longer a novice. I defended my thesis, we’re working on publications, and by and large I’ve put the Rapunzel Project to rest (I even retired the blog!).

All that being said I’m thrillingly eyeball deep in my PhD (first committee meeting: check!), and my research is actually rolling along in advance of my first field season (patting myself –very lightly – on the back). I’ve been giving talks on my research, and the blog posts are rolling out in various forms and locations. With all of this communicating about my research I became aware of something, my project didn’t have a name. Now I know that naming each project isn’t mandatory. Some people name their cars, some don’t; some people name their research, others don’t. But I have to admit writing the words “my dissertation research” over and over has grown tedious. As someone who values accessible communication as well as the role of creativity in science, I reached out to my fellow lab mates and asked for help with a name.

Calypso as she wistfully watches the sea... for humpback whales of course

Calypso as she wistfully watches the sea… for humpback whales of course

Suggestions varied wildly (“Life is the bubbles” anyone? How about a Calypso reference… so much fun). The name we settled on was astutely suggested by none other than ORCAA’s Selene Fregosi (maybe that writing workshop she wrote about helped with more than just her thesis). Without further ado let me introduce you to ORCAA’s Acoustic Spyglass: investigating the impact of vessel noise on humpback whale non-song behavior from the shores of Glacier Bay National Park.

I’m please with this name because (a) it incorporates both the visual and acoustic elements of the study, (b) because the use of a hydrophone array to localize animals is quite literally a form of “acoustic spying”, and (c) the use of a spyglass implies both antiquity and a sense of looking forward. When you pair visual observations with passive acoustic monitoring you are often looking forward (to the sea, tracking whales), but often technological constraints require that you listen retroactively after the hydrophones have been recovered. In this way I am quite literally listening to the past.

Listening to the Past

Nowhere is this more poignant than in the first chapter of the Acoustic Spyglass (see that… not “my dissertation research”), where I investigate non-song call stability at the decadal scale. I’ve acquired recordings of non-song vocalizations in North Pacific Humpbacks from the mid-1970’s through present day. I’ve been reviewing these to assess if non-song vocalizations, similar to song, change rapidly with time, or if humpbacks exhibit vocal stability. It is well known that humpback whale song changes annually, and this change is believed to be culturally mediated. Little is known, however, about how non-song vocalizations stand up to the test of time. Understanding the stability of non-song vocalizations may tell us something about call innateness, and may provide clues into how these vocalizations are used. Further, if non-song vocalizations (or specific types of non-song vocalizations) have been relatively stable for the past four decades then they may act as a metric against which to quantify change in the face of a shifting baseline (increasing ocean noise, climate change).

What’s so exciting (to me and possibly the ~twelve people who study non-song communication in humpback whales) is that based on first glance at least one call type – the SEAK Whup call – is remarkably stable over time! I’ve detected this vocalization in every data set currently in my possession. I want to be clear, that these findings are anecdotal at this point.  I’ve only just started quantifying my samples, and I have a long way to go before everything is sufficiently measured and described.  But from first glance would you agree that these two spectrograms look pretty similar?

"Whup" calls, R-L: 1976, courtesy of Roger Payne; 1982 courtesy of Greg Silber and Adam Frankel; 1995 courtesy of Fred Sharpe

“Whup” calls, R-L: 1976, courtesy of Roger Payne; 1982 courtesy of Greg Silber and Adam Frankel; 1995 courtesy of Fred Sharpe

There’s something magical about listening to vocalizations that were produced in the 1970’s and hearing some of the same purrs that I’ve grown familiar with.  That the scientific community forty years later is just now beginning to investigate what these non-song vocalizations mean is a testament to the breadth of research yet to be done on Southeast Alaskan humpback whales.  Humpback whales are long-lived, with lifespans that can reach 90+  years.  This means that the whales in these historic recordings may still be vocalizing in Southeast Alaska today.  Or perhaps these recordings may be a link between a previous generation of whales and those who have only recently made it to Southeast Alaska to forage.  In either case the analysis of this long-term acoustic data set is the first step to answering some of the basic questions about how humpback whales communicate and I’m extremely excited to be listening.

~This work is extremely collaborative. Data contributions have been made my individual researchers referenced above as well as the National Park Service, and the Alaska Whale Foundation~

***Follow my personal research blog here, or check out my lab’s blog blogs.oregonstate.edu/bioacoustics for a broader view of bio-acoustic research***

What Does Sound Look Like?

Before I can begin running analysis on the data we collected over the summer it first must be processed.  While I may have dreamed of attending to data in the field (and to a degree  that was done) the bulk of the data processing is being done retroactively. Preparing sound files for analysis is easily the most labor intensive part of this research phase.

We collected over 300 sound files, and a minimum of 248 of them require fine scale attention.  This means that  every vocalization our interns heard in the field while floating  in Noble Stead must be listened to again during the verifying process, again as I measure its parameters, and yet again as it is placed into a broad vocal category.  Sounds were initially categorized by ear as we intuitively began to recognize certain call types.  They are further categorized, however, not by ear but by sight.  For each sound listened to (once, twice, three times listened to) I create what’s called a spectogram- or a picture of the sound.  This picture allows us to see the shape of the sound, the duration, the frequency, and the modulations.  Obviously, things that look the same should sound the same.
So, what do humpback whale calls look like?  Like this-

 

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