A University of Alaska Fairbanks researcher who listens to killer whales using underwater microphones, called hydrophones, has learned some interesting things about the creatures.
Hannah Myers is a Ph.D. marine biology student with UAF’s College of Fisheries and Ocean Sciences. A recent paper Myers co-authored in the journal Scientific Reports delves into the mysteries of where North Pacific killer whales spend their time in winter and which of their undersea calls originate from which pods or ecotypes, which are like subspecies.
Myers says the most abundant of the three main ecotypes living in the waters off Alaska’s coasts are the resident killer whales, which vocalize distinct, repeated calls that can be used to identify them.
The following transcript has been lightly edited for clarity.
Hannah Myers: So when I hear a particular call in a recording, and it’s a resident killer whale, I often know which family group is present or which pod is present. So, obviously, it’s pretty tough to do winter fieldwork on the water in Alaska due to, you know, really nasty weather, limited daylight hours. And so we only had data from May to October. And that’s where this acoustic study was really something brand new. So questions that we had: Where can we find the whales in the winter? What might they be doing there? Is it the same whales? Is it somebody different? Things like that.
Casey Grove: So hydrophones, I mean, describe the process to me of actually going and using those. You have to take them out, drop them down, you said, and then you have to go pick them back up, right?
HM: Yeah, we do. And it’s always kind of an exciting and nerve-racking process. We put them on an anchor and drop them overboard and then come back to our GPS points a year later, and we actually grapple for them — so drop out a hook over the side of the boat and try and pick up the line connected to the hydrophone and bring it back up. And we’ve actually had pretty remarkable success doing that in over 100 feet of water. It’s always an exciting and relieving feeling when that line comes over, and the hydrophone comes up with it covered in, you know, all kinds of algae and weird invertebrates growing on it close to the sea floor over the course of a year. But yeah, scrape those off, get her cleaned up and open it up and take the the memory cards out and replace the batteries and drop it back down.
CG: That almost sounds like “Deadliest Catch” to me or something with the hook. So, you extract this audio from the hydrophone, and we actually have a clip of some of that I’m going to play right now.
Killer whales: (whale calls)
HM: What we’re hearing there is the 8016 pod. And that’s a group of 13 whales, resident fish-eating whales. And in that group we have a grandmother and her three brothers, her three adult daughters, adult son and then her daughter’s offspring. So resident killer whales are thought to be unique among mammals, in that both their female and male offspring stay with the mothers for life. And so in this recording, you can hear sort of the two main call types that are part of that 8016 dialect that I mentioned. We sort of have nicknames for the different calls. So in that recording, you heard the “hey” call, and then the three-tone call. And whenever I hear those, I know that the 8016s are present.
CG: So they’re literally saying, “hey,” in at least one of those calls?
HM: Well, I wish I knew what the whales were actually saying to one another, but I don’t, that’s just what we’d nickname it, because it almost sounds like someone yelling, “Hey!” But yeah, I mean, it’s thought that these unique dialects are probably useful for group identification for the whales, since they have this really important social structure. We sometimes compare it to if you were running around shouting your last name sort of.
CG: “Myers! Myers!”
CG: We all do that at family gatherings from time to time. That’s super interesting. And what about your research, what results surprised you the most?
HM: Yeah, there were a few things that surprised me about this work. So we dropped the hydrophones in areas where this long-term monitoring had showed the killer whales could be found pretty reliably during summer months. But, like I said, we really had no idea if they were going to be there in winter or not. We just didn’t know where they were going to be. And we found really high use throughout the winter in some areas, and especially Montague Strait, which is the western entrance to Prince William Sound. So on some winter months, we were hearing killer whales, you know, nine out of 10 days, which was really surprising because a lot of the time when we document whales in a given area, there’s a clear correlate with that, like a Chinook salmon run that we would expect them to be interested in, you know, being in that area to eat that salmon. But obviously that’s not happening in winter. So it’s a big mystery, you know, what it is that they’re out there for at that time. And then another thing that was pretty exciting about this study is recording the mammal-eating killer whales as much as we did. They, on average, are a lot quieter than the fish-eating killer whales because their prey can hear them, so they can’t really afford to be vocalizing a lot. That being said, we did record them. We have the Gulf of Alaska transients, and this is thought to be over 100 — possibly several 100 — animals, but we didn’t really have good recordings of them that we could use to identify them on the hydrophones. And so we were hearing this group of calls on the hydrophones pretty consistently, one of them we nicknamed the “rooster call” because it sounded exactly like a rooster crowing. And it was sort of this mystery, like, who’s making these calls? And a researcher we collaborate with, she actually recorded a group of Gulf Alaska transient killer whales in Kachemak Bay in August 2020 and photo-identified them and got this really amazing recording that included those calls. That was a really exciting part of the study, solving the rooster mystery.