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Discovery Channel

How Scientists Built a Shark-Following Robot for Shark Week

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Discovery Channel

For all we know about sharks, there's still a lot we don't know about these animals that both fascinate and terrify us. Traditional tracking methods like satellite and acoustic tags have shed some light on shark behavior, but even they have their limitations.

That's where Shark Cam, an autonomous underwater vehicle, comes in. "A few years [ago], I was working with a scientist who loved the idea of trying to find out what some of these fish that we track do when we can’t follow them because they’re out of reach or they go deep or we disturb them when we get in the water," says marine biologist Greg Skomal. "We thought it’d be really interesting to develop some kind of robot that could track marine animals, specifically sharks. One of the principals at Big Wave Productions [which produces shows for Shark Week] was super excited about the concept and propelled it upwards to Discovery, and they loved it. So with their support, we were able to actually make this come to fruition."

The autonomous underwater vehicle (AUV) was developed by Skomal and scientists at the Oceanographic Systems Laboratory at Woods Hole Oceanographic Institution. It was deployed from a boat off of Chattam, Massachussets, last year, where it followed great white sharks as they swam along the coast. Shark Cam makes its debut in the Shark Week special "Return of Jaws" tonight at 9 p.m. EST on the Discovery Channel; we talked to Skomal about developing the robot and what it revealed that traditional tracking methods did not.

How long did it take to build and deploy Shark Cam?

We started the project in 2011, and were able to do some field trials in late 2011, and we had a pretty functional vehicle by the summer of 2012. So about a year of solid development. Most of that was software modifications by the engineers who run these robotic underwater vehicles.

When you’re building something like this, are you working from an existing platform or are you starting from scratch?

The Oceanographic Systems Laboratory at Woods Hole Oceanographic Institution has an existing group of vehicles that are autonomous—they’re completely untethered to the boat, and they can be programmed to do a variety of missions. So really, all we had to do was modify the software of one their existing vehicles in order to get it to follow a live shark.

It sounds simple, but it wasn’t. It was a partnership—[between the engineers and] me, having tracked fish for years, trying to give them a sense of what we anticipate the behavior of the shark to be, so that the vehicle can adjust to it. It’s one thing to have a vehicle go in a straight line, or even mow a lawn—back and forth, back and forth—but to have it adjust to the behavior of a live animal is a most complex process.

What kind of behaviors would they be adjusting for?

Changes in three-dimensional movement. Up, down, sideways, back, forth—you name it. Very few live animals swim in a straight line at one depth. So it had to basically adapt to random movements in three-dimensional space.

What technology did you outfit the robot with?

There were four cameras on Shark Cam—it was specially designed to carry three of those, and one mounted on top. It's battery-powered, which limits its life, but that’s fine, we can expand on that. It is modular in the sense that we can add components to it that do various kinds of things that we did not do [on this mission], like collect oceanographic data. It communicates with a transponder that we put on the shark to follow it and navigate and recreate the track of the animal.

We actually added a rear-facing camera, but because of the fine balance on the vehicle itself—it’s a torpedo and it has to be extremely hydrodynamic—throwing the extra camera on slowed it down. So that’s something that we have to develop in the next phase of this operation.


Robot with a view. Photo courtesy of the Discovery Channel.

When you decided you were going to take the Shark Cam out and put in the water and send it after a shark, you guys had to go out and tag the shark first. How did the robot work in conjunction with the acoustic tags?

We’ve been tracking white sharks with a variety of technology off the coast of Cape Cod for the last four summers. So [tagging the sharks was] almost the easiest part, since we’d already done the [research and development] to get that done. Once we got the transponder on the shark, the AUV was set to go.

Most acoustic transmitters emit a ping, and the ping is picked up by people in the tracking vehicle, so we can track the fish. But this acoustic tag is a transponder, so it has two-way communication between the vehicle itself and, in essence, the shark. So we can basically have a conversation that provides for highly precise navigation and mapping of three-dimensional movement. And that really is a step forward, because it’s not just passive acoustics where you’ve got a vehicle trying to just listen for something. [The AUV] was actually listening and communicating with [the tag].

We had to program the vehicle so that it could make decisions—very simple cause and effect decisions based on where the shark was, to follow it. We ended up getting a vehicle that can give us very precise tracks of the animal.

Were there any glitches you had to work out?

There was a whole series of glitches. The transponder itself is larger than we want it, but the funding simply wasn’t there to miniaturize it. So we had to use what we had. It turns out the orientation of the existing transponder design had to be vertical in the water column, which is absolutely counter to normal hydrodynamics. We had to figure out a way to get it to tow vertically on the shark, and that took a few days working with our tagging crew and the engineers. And that would allow for a stronger signal so that the AUV could actually keep up with the shark in shallow water.

We’re also in the natural environment. Where these white sharks hang out is a very dynamic area in terms of tide and current. So in many ways, we’re up against trying to get a vehicle that can only go, you know, six miles an hour to keep up with a shark that was swimming steadily at five miles an hour. And then it was the fine-tuning of the vehicle so that it could stay with the shark and not lose it.

How did the sharks react to it?

Jokingly, I told the engineers that once this big white shark sees this vehicle, painted bright yum-yum yellow, it was going to turn around and just eat it. Most would think that this voracious animal that is considered to be one of the most dangerous one on earth would not like to be followed so closely. So these guys got nervous every time the AUV got in close proximity to a shark.

But the shark completely ignored it. [At one point,] the shark actually turned around and did a big loop and started following the AUV, which I thought was fantastic. The AUV couldn’t do anything about it—it was hearing the shark behind it, and a major limitation of the technology is that it can’t do hairpin turns and quick circles. So that made for some good humor.

What did you learn by deploying this robot that you couldn’t learn just from using acoustic tags or satellite tags?

Every tag in technology has its ups and downs, and there’s no silver bullet when it comes to tags that gives you high resolution, broad scale, and fine-scale data on movement. Satellite tags are really good for looking at broad-scale movement—where the shark goes in broad migratory patterns. It doesn’t tell you a lot about fine-scale behavior.

Acoustic tags will tell you a little bit about fine-scale behavior, but only in the sense that you know where the shark is at any given time. One of the problems with the technology of acoustic tags—prior to us doing this—was instead of sending a robot after a shark, you follow the shark with your boat. And that’s usually limited by weather considerations, fuel, compatibility of crew members, provisions, all those things that can come up and go wrong. And the boat’s track doesn’t necessarily reflect the shark’s track, because the shark is going to be somewhere within a quarter or a half a mile from the boat. And it’s really hard to get a good, precise estimate of the actual movements of the shark in three-dimensional space using traditional tracking methods.

With the ability to send robots after the shark, you’re going to increase the precision of your tracking so you’ll know exactly what the shark did in three-dimensional space—the depth of water, the depth of the shark—and you’re collecting data at the same time over that same path. The vehicles can carry instrumentation on them—the simplest being water temperature, to complex instrumentation that measures current and tide—so you can determine whether the shark is swimming upstream or downstream. You can look at dissolved oxygen, so you can get a sense of what the minimal oxygen requirements of the shark are. You can also add other kinds of instrumentation that’ll answer questions about the habitat in which the shark lives.

So it’s a huge step forward—and when you throw cameras on the whole thing, you even have the potential for real behavioral observation: To see what the shark is doing. Let’s say it stops swimming and just stays in one area. If we approach it and put divers in the water, that’s going to spook the shark—and very few divers want to jump on top of a white shark to begin with. Or you speed up on it on a boat and you try to see what the shark is doing, but what if it’s 30 feet underwater? You can’t see what it’s doing. You send Shark Cam out, and you can record what’s going on in that area.

So the robot is a proxy for what we can’t do, and I think it’s a huge step forward in terms of advancing science and adding a new tool for marine scientists.

Have you used Shark Cam since?

We have not deployed the Shark Cam since last summer. The next step is going back to the drawing board—raising funding to tweak it and take it to the next level.

What's the next level?

The next level for us is to improve upon and learn from what we’ve already done. It’s a real solid analysis of the data, it’s fine-tuning the software to take into account sudden modifications in the shark’s behavior. It’s probably to integrate the camera systems a little better with the AUV so that we may be able to control them—turn them on, turn them off. It’s energy budgeting. And it’s really miniaturizing the transponder so that we can put it on much smaller sharks and maybe broaden its applicability.

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Big Questions
Why Can't Dogs Eat Chocolate?
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Even if you don’t have a dog, you probably know that they can’t eat chocolate; it’s one of the most well-known toxic substances for canines (and felines, for that matter). But just what is it about chocolate that is so toxic to dogs? Why can't dogs eat chocolate when we eat it all the time without incident?

It comes down to theobromine, a chemical in chocolate that humans can metabolize easily, but dogs cannot. “They just can’t break it down as fast as humans and so therefore, when they consume it, it can cause illness,” Mike Topper, president of the American Veterinary Medical Association, tells Mental Floss.

The toxic effects of this slow metabolization can range from a mild upset stomach to seizures, heart failure, and even death. If your dog does eat chocolate, they may get thirsty, have diarrhea, and become hyperactive and shaky. If things get really bad, that hyperactivity could turn into seizures, and they could develop an arrhythmia and have a heart attack.

While cats are even more sensitive to theobromine, they’re less likely to eat chocolate in the first place. They’re much more picky eaters, and some research has found that they can’t taste sweetness. Dogs, on the other hand, are much more likely to sit at your feet with those big, mournful eyes begging for a taste of whatever you're eating, including chocolate. (They've also been known to just swipe it off the counter when you’re not looking.)

If your dog gets a hold of your favorite candy bar, it’s best to get them to the vet within two hours. The theobromine is metabolized slowly, “therefore, if we can get it out of the stomach there will be less there to metabolize,” Topper says. Your vet might be able to induce vomiting and give your dog activated charcoal to block the absorption of the theobromine. Intravenous fluids can also help flush it out of your dog’s system before it becomes lethal.

The toxicity varies based on what kind of chocolate it is (milk chocolate has a lower dose of theobromine than dark chocolate, and baking chocolate has an especially concentrated dose), the size of your dog, and whether or not the dog has preexisting health problems, like kidney or heart issues. While any dog is going to get sick, a small, old, or unhealthy dog won't be able to handle the toxic effects as well as a large, young, healthy dog could. “A Great Dane who eats two Hershey’s kisses may not have the same [reaction] that a miniature Chihuahua that eats four Hershey’s kisses has,” Topper explains. The former might only get diarrhea, while the latter probably needs veterinary attention.

Even if you have a big dog, you shouldn’t just play it by ear, though. PetMD has a handy calculator to see just what risk levels your dog faces if he or she eats chocolate, based on the dog’s size and the amount eaten. But if your dog has already ingested chocolate, petMD shouldn’t be your go-to source. Call your vet's office, where they are already familiar with your dog’s size, age, and condition. They can give you the best advice on how toxic the dose might be and how urgent the situation is.

So if your dog eats chocolate, you’re better off paying a few hundred dollars at the vet to make your dog puke than waiting until it’s too late.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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Animals
Elusive Butterfly Sighted in Scotland for the First Time in 133 Years

Conditions weren’t looking too promising for the white-letter hairstreak, an elusive butterfly that’s native to the UK. Threatened by habitat loss, the butterfly's numbers have dwindled by 96 percent since the 1970s, and the insect hasn’t even been spotted in Scotland since 1884. So you can imagine the surprise lepidopterists felt when a white-letter hairstreak was seen feeding in a field in Berwickshire, Scotland earlier in August, according to The Guardian.

A man named Iain Cowe noticed the butterfly and managed to capture it on camera. “It is not every day that something as special as this is found when out and about on a regular butterfly foray,” Cowe said in a statement provided by the UK's Butterfly Conservation. “It was a very ragged and worn individual found feeding on ragwort in the grassy edge of an arable field.”

The white-letter hairstreak is a small brown butterfly with a white “W”-shaped streak on the underside of its wings and a small orange spot on its hindwings. It’s not easily sighted, as it tends to spend most of its life feeding and breeding in treetops.

The butterfly’s preferred habitat is the elm tree, but an outbreak of Dutch elm disease—first noted the 1970s—forced the white-letter hairstreak to find new homes and food sources as millions of Britain's elm trees died. The threatened species has slowly spread north, and experts are now hopeful that Scotland could be a good home for the insect. (Dutch elm disease does exist in Scotland, but the nation also has a good amount of disease-resistant Wych elms.)

If a breeding colony is confirmed, the white-letter hairstreak will bump Scotland’s number of butterfly species that live and breed in the country up to 34. “We don’t have many butterfly species in Scotland so one more is very nice to have,” Paul Kirkland, director of Butterfly Conservation Scotland, said in a statement.

Prior to 1884, the only confirmed sighting of a white-letter hairstreak in Scotland was in 1859. However, the insect’s newfound presence in Scotland comes at a cost: The UK’s butterflies are moving north due to climate change, and the white-letter hairstreak’s arrival is “almost certainly due to the warming climate,” Kirkland said.

[h/t The Guardian]

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