On Cape Cod beaches, worries about great white sharks spike each summer, especially in light of the two shark attacks last year, one of which was fatal. A new study is about to get underway, aiming at understanding the behavior of great white sharks.
Greg Skomal, with the state's Division of Marine Fisheries, is one of the study’s leaders. Skomal spoke with WGBH All Things Considered anchor Barbara Howard about the study. This transcript has been edited for clarity.
Barbara Howard: Well first off, how nervous should Cape Cod swimmers be as they wade into the water this summer?
Greg Skomal: Well I don't think it's any surprise that the sharks are out there. They've been coming for the last decade or so and the numbers are apparently increasing, so it's not new that they're there, and I think people are adapting to their presence. The two negative interactions last year — the bite on the swimmer and the fatal attack — has people on edge. And I understand that.
Howard: Now I know you've studied great white sharks, especially off Chatham, with that colony of seals there. The sharks, though, have spread beyond Chatham, following the seals. Can you talk a bit about that?
Skomal: Well, we've been seeing seals all along the outer Cape, just because there's a dense colony south of Chatham. There's also seals off Orleans and all the way up in Truro, and then even in Cape Cod Bay. So it seems that the seals are dynamic, they're moving, and the sharks are right behind them.
Howard: Has that expanded, though, the number of seals? It seems as though we didn't have attacks, certainly not fatal ones, until recent years.
Skomal: I think the number of seals has been on a steady increase and the sharks are hunting all along those areas in an effort to get to the seals.
Howard: Is there any place that's safe?
Skomal: One of the things we've been trying to do is get a relative sense of where the sharks are in the greatest densities. And it turns out that parts of the outer Cape, as well as Cape Cod Bay, particularly the eastern side of Cape Cod Bay, is where the highest densities and the greatest abundance of sharks are. There are places in Massachusetts — Nantucket Sound, Vineyard Sound, Buzzards Bay, and as you move west and north along the Massachusetts shoreline — where there's very few great white sharks, so virtually all of those areas have low densities and are absolutely safe to go swimming in deep water. It's not until you get out to the outer Cape that I'm concerned about going into those deeper areas.
Howard: So between which towns are we talking about, roughly, where you consider the densest concentration?
Skomal: Basically, the entire outer Cape from Provincetown south to the southern tip of Monomoy.
Howard: Well now you're starting this new study to track the sharks better. Talk about that.
Skomal: Well one of the things that we've learned over the years is that when you've got a lot of overlap between sharks and their prey — the seals — with people, the probability of a negative interaction, of a bite or shark attack, goes up. We think the best way to try to prevent shark attacks is a better understanding of the predator-prey relationship between sharks and seals. To boil it down to a single sentence, we're trying to figure out where, when, and how sharks attack seals, and we think that a really good understanding of how that's happening will give us the kinds of information we can use to advise swimmers, beach managers, and public safety officials.
Howard: How are you going about figuring that out?
Skomal: Well it's understanding where and when they're actually making these attacks, and there are a number of ways of doing that. One is to directly observe it. But one of the things we've learned over the last decade is that these sharks are spread out over such a broad area that the idea of sitting there and waiting for a shark to attack a seal and understanding how that's happening is pretty improbable. So we're using new technologies that have emerged over the last decade that will give us a sense of the actual behavior of these sharks, and by affixing these technologies to the sharks, we can not only see their very, very fine scale movement, but also get actual recordings from camera systems of what the sharks are doing so we can actually tell when the sharks are attempting to feed on seals, where they're attempting a feed on seals, and how they're going about doing that.
Howard: So these aren't tags to actually monitor the sharks — to set off the alarm, everybody out of the water, here comes a great white shark. This is more just to understand their habits and monitor them as they swim along?
Skomal: That's exactly right. We really want to understand their habits, their patterns of behavior, their movements, where and when they spend their time. There are systems available that will provide warnings to swimmers if one of our tagged sharks swims within the range of one of those systems, one of those acoustic detection systems. They're very expensive, but they are available, and we're probably going to try to deploy a couple of those this year to test the technology.
Howard: Any advice for people who still go in the water under those conditions? Is there anything they should or should not, for example, be wearing?
Skomal: There's nothing definitive. Let's face it, though — the sharks are hunting seals. Typical surfers wearing a wet suit look a little bit like a seal, and act like a seal at the surface. And so you know, anything that would break those similarities of course would be recommended.