Feb 17, 2009

National Geographic's Critter Cam: Using CNC to Study Shark Behavior

Greg Marshall, a marine biologist, was scuba diving in Belize in 1986 when he saw a suckerfish hitching a ride on a shark’s belly. “What if I could attach a video camera to that shark?” he thought, “follow it where no human could go, and see the ocean as the shark does?”

To make this idea a reality, Marshall devised a waterproof fiberglass housing, placed a video camera inside, and attached it to the back of a captive sea turtle, which didn’t even notice that it was there. This prototype Crittercam, as Marshall dubbed it, demonstrated that a camera could be attached to a sea animal without affecting its behavior. A second test on a wild sea turtle failed, however, when the camera came loose and disappeared. In 1990, the National Geographic Society began to fund Marshall’s project and it took off. Soon he deployed Crittercams on sharks, sea turtles, and fur seals.

Since then, more than 30 groups in government and academia have used Crittercams to study the hidden lives of marine and terrestrial animals all over the world. In more than 400 deployments, Crittercam has provided new information about how more than 40 species of sharks, sea turtles, whales, seals, and penguins communicate, stake out territory, hunt, and mate.

Today’s Crittercam is much improved over earlier models. Marshall and his team at National Geographic’s Remote Imaging Program in Washington, DC, have devised adhesive patches, suction cups, clips, harnesses, and collars to attach the cameras to animals. They’ve lightened the Crittercam from the original six lb-plus to less than 1.8 lb today and have reduced diameter from six-in. to 2.25-in. Present-day controls are more accurate and functional; the cameras can record in color for up to six hours.

Crittercam brings “the animal’s point of view to the scientific community and a conservation message to worldwide television audiences,” says Marshall. It’s been featured many times on National Geographic’s Wild Chronicles series.

How it Works

The Crittercam is an “animal-borne video and data logging system designed for studying the at-sea behavior and ecology of large marine invertebrates,” Marshall states. The Marine Crittercam is a streamlined water- and pressure-proof system with an internal headlight and a video camera that records images onto an SD memory card. Engineered and machined to meet tight tolerances, the housings may be aluminum, which operates to depths of 1,000 meters, or titanium, which can withstand water pressures at depths of 2,000 m or more.

An on-board user-programmable microcomputer controls the Crittercam’s image logging and data logging capabilities. Since each marine animal is different and research goals vary with each project, Marshall’s team varies the Crittercam design for each user and orders small quantities. Crittercams typically price out between $7,000 and $13,000.

Researchers program the Crittercam’s internal computer to release it at a specified time. Equipped with floats, the housing rises to the water surface, where a radio signal facilitates tracking and retrieval. Since 1986, only three percent of all Crittercams have disappeared at sea.

The Crittercam team has created a terrestrial model, which is collar-mounted and does not record. It uses radio waves to transmit video, sound, and other data to receiving and recording stations. To retrieve the terrestrial Crittercam, researchers transmit a radio signal that releases the collar, which they track down with radio. Terrestrial models have been attached to lions, hyenas, grizzly bears, and even (once) a house cat.

Key Step

Deployment is a key step in the Crittercam process. When scientists work with a shark, they lure it next to their boat and use a ten-lb., seven-foot-long aluminum deployment pole to drop the Crittercam quickly and painlessly onto the shark’s dorsal fin so nothing seems amiss. A clip with remote release holds the camera on.

A pneumatically operated mechanism at the tip of the deployment pole holds and releases the camera, says Graham Wilhelm, design engineer. The design team adapts the pole for different combinations of camera and marine animal, but a typical assembly consists of 17 machined parts plus stock parts like fasteners and pneumatic tubes. Five units may be ordered at a time, often on short turnaround.

Want the Order?

Five each of 17 parts is not an order that most machine shops would welcome, but Frank Borke, owner and sole employee of Master Pattern, Lafayette, Colorado, thrives on this kind of work. He machines all non-stock parts for Crittercam deployment poles and floats for the camera. National Geographic adds stock parts and assembles the pole. Borke machines 6061 aluminum tube primarily and makes some parts from sheet depending on the geometry. The total order is 17 different pieces, including duplicates for disposable and wear parts. Turnaround can vary from a few days to two weeks.

“The Crittercam design team doesn’t produce big orders because everything is specialized,” Borke says. “When they want to tag a new animal, they come to me with CAD drawings. I make occasional design suggestions, machine ten sets maybe, and that’s it.”

Borke makes out on Crittercam and similar prototype and small-scale, short-run business because he has a machining center from Tormach, Inc., a three-year-old firm in Waunakee, Wisconsin. Borke purchased Tormach’s PCNC-1100 model equipped with the optional fourth-axis rotary table and duality lathe. It runs on single-phase power.

The Tormach machining center came to $11,000 with all accessories. Options raised its price into the $15,000 to $16,000 range. Borke estimates that he’d have to pay “at least $35,000” for similar equipment from a major machine tool maker.

Greg Jackson, Tormach president explains that the Tormach’s “big advantage is a combination of affordability and precision. Our machine meets ±0.001-in. tolerances,” he states. “It’s perfect for low-overhead shops that do prototyping, custom manufacturing, and small-scale production. Everybody benefits because Tormach makes this type of manufacturing affordable to do and to buy.”

Says Borke: “I’ve had machining centers from major manufacturers, but I replaced them with a Tormach to get away from expensive three-phase power so I could have a smaller, more portable shop and move to an outbuilding on my property. Ultimately I want to run on solar power.

“Before I bought, I did a lot of research, comparing different machines,” Borke continues. “Tormach let me do more at less cost. It’s helping me grow my business and keep it lean. If I needed another machining center, I’d order a Tormach—and I absolutely recommend it to others.”

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