Navy sonar: Background

Imagine that you're a dolphin peacefully swimming through the sea, with all of your buddies, happily hunting fish. You're squeaking and whistling to your friends, communicating all sorts of information to them, and they're squeaking and whistling right back. You're also echolocating to find the fish - you're making constant little "clicks", and all around you, you can hear echoes of the clicks coming back from the fish that you're trying to catch. You're also keeping an ear open for killer whales.

In a nutshell, you're exquisitely sensitive to every sound in the sea.

So you're swimming along, and all of a sudden:

BONG!!!!!!!!!!!!!!!!!

... the loudest sound that you have ever heard in your life blasts out from a U.S. Navy ship a mile away. You're so dazed afterwards that you can't seem to hear right.

What happens next?

Nobody knows!
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The U.S. Navy periodically uses a type of sonar that is so loud that there has been a concern that the sonar might affect, or even kill, marine mammals that are near the ships. It's called "low frequency active sonar", and its purpose is primarily to detect quiet submarines. Navy ships emit these sonar pings at astonishingly high decibel levels - up to 180 dB and higher, sometimes over 200 dB. If you were sitting in the water next to one of this ships, the sound level would be the equivalent of standing next to a NASA rocket at takeoff. But just for a fraction of a second, which is how long the "ping" lasts.

When the Navy started using this kind of sonar, there occurred some "mass strandings," events in which whole groups of whales (usually a type called beaked whales) suddenly piled up on beaches - and died. This happens occasionally all over the world; there are always some mysterious mass strandings that happen for unknown reasons. It's always been a puzzle what causes mass strandings. But in a couple of cases, the strandings occurred directly after a Navy sonar exercise nearby. So the Navy started to come under increasing public pressure to demonstrate that they were not harming marine mammals.

In conservation biology terms, the Navy is creating a unique type of habitat degradation - acoustic disturbance. It's not a contaminant, it's not pollution, it's not a fishing net. It's just noise. But it's VERY LOUD noise, and it's not natural for that environment. What might it be doing to the animals?

The first suspicious strandings were noticed in the early 1990s, and since then the Navy's been focusing on this issue more and more. They now have several people working full-time, year-round, on "the marine mammal problem", as they call it, looking for a "solution" - by which they mean, a clear answer, about exactly what volume of sonar causes exactly which problems in marine mammals, at exactly which distance, and exactly how that affects the animals' health, welfare, reproduction and survival afterwards. They need a clear answer in order to know how much they need to quiet down their sonar pings, and under what conditions they shouldn't use sonar at all.

Yesterday I talked to the guy who is in charge of the entire Navy marine mammal program. He told me "You wouldn't believe how far the Navy's come about awareness of this issue. I've been working on this since maybe the mid 90's, and I talk to everyone in the Navy, from the top down. I talk to the secretary and all the generals. At this point, every single four-star general in the Navy, every single one of them, knows all about the "mammal issue". When I walk through the Navy offices, people all know who I am and what I'm working on - they're always calling out 'Hey, it's the mammal guy! Hi mammal guy! Mammal guy, have you solved the problem yet?' "

He added, "And I always say 'Not yet.' "

He went on, "They started off giving me a budget of $700,000 a year to fund research on this problem. That was ten years ago. Now it's $10,000,000 a year."

Actually this coming year it will be $12,500,000. They keep doing more and more research, because the "clear answer" they're seeking gets more and more murky.

Interestingly, the Navy's already solved the major problem: Stopping the strandings. Quoting again from my new Navy friend (paraphrasing, actually - I didn't have a tape recorder so this is from memory): "There's no doubt those couple of early strandings in the 90's were caused by us. We caused those strandings. That was our fault. Clearly. So I studied everything about those events and I made up a list of the conditions that had contributed to the strandings. And now we use that list to decide when not to use sonar."

I asked about the "conditions" and he started reeling off descriptions of exactly which stranding, where, in which year, was related to sonar, and every single detail about each of those strandings - from the number of animals to the species to the weather that day. It became apparent that he knew, by heart, the details every single marine-mammal stranding event in the world in the last 20 years (so did most other people nearby, who were chiming in details like, "Tell her about the Canary Islands!" "Tell her about the melon-headed whales!").

He concluded with: "Here's my list: A deep, narrow channel with no egress. Whales in the channel, especially beaked whales. A shallow ramp out of the channel that goes up to a sloping beach. Three Navy ships cruising back and forth at the other end of the channel. Multiple ships all doing the sonar at once." That'll cause a stranding, he said.

I asked, what's Navy policy now?

He said: "What has happened is, I got them to use my list, and today it is FORBIDDEN in the US Navy, it is absolutely VERBOTEN [you could hear the capital letters in his tone of voice], to do a sonar exercise when those conditions are in place. The conditions of my list. We absolutely never use the sonar in that situation. And we have not had a single mass stranding in ten years caused by the U.S. Navy. That is, not counting those events where a mass stranding occurs for some other reason and the media all says "Oh, there was a Navy ship here doing sonar exercises only a month ago, a thousand miles away, so it must be due to that!" That is the most frustrating thing.... Yes, there have been mass strandings caused by navies recently, but it's not the US Navy. It's the European navies! Because the European navies don't use my list. Actually they don't really have any tough sonar regulations in place. They don't have a clearly defined set of criteria of exactly when they must not use sonar."

He added one more detail: "Oh, and, if we're doing a sonar exercise in any other location, if there's any marine mammal sighted, the sonar is turned down, and if it swims closer to a certain level it's turned down further, and further."

So I asked if a dolphin could "turn off" a Navy ship entirely just by swimming right up to it, and he said "Yes, sure, that happens sometimes." (And I wondered whether some dolphins might actually learn to do that on purpose.)

So here is my impression of where it stands right now: The mass-strandings are not happening any more (not with our navy, anyway), and the Navy's got a pretty good policy of not using sonar, or turning it down, when marine mammals are known to be nearby. It's also become apparent, after an immense amount of testing, that the sonar doesn't kill the animals outright and (at the levels and distances typical in the sea) does not physically damage them. Or as he put it "The sonar's not a Death Ray. It's really not."

But - even if they're not dying, even if they're not stranding, couldn't the sonar still be affecting the animals somehow? Basically: does it STRESS the animals, in some way that might affect their health or survival later?

For example, consider these three possibiltiies:

- Hearing. Loud sonar has been shown (by Navy-funded research) to make a dolphin's hearing less sensitive temporarily. It's called a "Temporary Threshold Shift" - a temporary shift in the threshold of hearing. It's the same effect experienced by a person who spends all night in a loud dance club, walks out on the street later, and realizes that he's shouting at his friends. Because everything sounds muffled. For the human, no big problem. But for an echolocating dolphin - could this ruin its ability to find food, temporarily? Or to communicate with its social group?

- Driving animals away. The most prominent behavioral reaction by beaked whales to sonar is simply that they stop foraging and leave the area for a few days. They just "go quiet, dive deep and leave" as one scientist put it. A couple days later, they come back, and they seem fine. But suppose the consequence was that they went hungry for a few days because of having to leave their feeding grounds. If this happens over and over, would they lose weight? Would they start starving, or not breed as often? Or - is it no problem? How can we tell if it is a problem for a beaked whale to move away for a couple days?

- Chronic stress. The most subtle effect is that loud sonar may simply cause an incresae in stress hormones. In other words, it might just "stress out" the dolphin (or sea lion, beaked whale, etc.), even though the animal might actually be physically just fine. The potential problem here is that long-term chronic stress is well-documented to interfere with health, reproduction, and the immune system.

So it has come down to this: How "stressed out" does a marine mammal feel after it's heard a loud sonar ping? And how often can a marine mammal get "stressed out" before its health, reproduction, and general quality of life really start to suffer?

At this point the Navy is groping for what to do next. They've pretty much stopped the mass strandings, they've shown the sonar doesn't actually kill the animals, but they know the public will not be satisfied with that. So they know they have to somehow tackle this vague, intractable question of: what makes a dolphin feel "too stressed out"?

So what they did was: they have invited all the top stress physiologists and all the marine mammal physiologists from around the world to come to D.C. for a two-day conference, to tell them the state of research in stress physiology, and to advise them what their research priorities should be. They sent out the call worldwide - they got pretty much every marine mammal researcher worldwide who has ever studied any aspect of stress, and they also invited most of the world's experts in general stress physiology. (I apparently got on the list because of a study I did some years ago on measuring stress hormones in North Atlantic Right Whales.) They flew us all here to Washington, D.C., paid our plane tickets, our hotel, our taxis and food and just asked us to talk to them for two days. They're going to use our advice to decide what to do with the $12,500,000 per year that they currently receive for research.

What I think they are only just realizing is that they have strayed into a research minefield. "What stresses a dolphin?" might seem like an easy question, but it's got to be one of the most difficult field biology questions possible. Because it's bedeviled by two of the most complicated and impossible questions of field biology:
(1) How can we study ANYTHING about marine mammal physiology - animals that we can't catch, can't take a blood sample from, and can't even see most of the time?
(2) How can we measure stress? What is stress anyway? What does "stress" even mean?

Poor Navy. I wonder if they know what they've gotten into! These are two of the thorniest problems in biology, and the best minds in the field have not solved either of them in over a century of trying. I once swore I would never get involved in stress research, becuase it's so difficult, so impossible to study, so impossible to get a clear answer; and I also once swore I would never get involved in marine mammals, because they are so difficult, so impossible to study, so impossible to get a clear answer.... So of course here I am at the Office of Naval Research's Workshop on Assessing Acoustic Stress in Marine Mammals.

Well, that's the background. And here we all are in DC!

posts coming next (to be written more slowly):
- summaries of some of the really exciting research projects that I am learning about
- a Navy lament, told to me over several glasses of beer at the Wednesday night social
- the Pie-in-the-Sky list: if you could have all the money you wanted to invent any new research technology to study marine mammals - if you could invent any crazy little robotic gizmo or sequence any genome, what would you do?
- What happens next?