YouTube fuels animal propulsion research
Biologist, students analyze videos of flying, swimming animals to define universal rules for bending
For many people, YouTube is a destination for video entertainment — a seemingly limitless repository of improbable skateboard tricks, choreographed wedding proposals, and adorable cat antics.
But for a group of current and former students at Providence College and Dr. John H. Costello, professor of biology, YouTube and other Internet video hubs serve as research databases.
Under Costello’s direction, a team of undergraduate students searched through the sites for animals in motion, such as fruit flies flying through the air or humpback whales swimming in the ocean, and analyzed the footage to find universal bending patterns for animal propulsion. The journal Nature Communications published their paper on the research February 18. Nature also published a commentary about their work.
“Because of the advent of YouTube and Vimeo, we can find out things we never could find out before,” Costello said.
His research has focused on how jellyfish move through water. These and other animals use wings, fins, or flexible structures to propel themselves, but manmade versions never work as efficiently.
About three years ago, Costello and Dr. Sean P. Colin ’93, associate professor of environmental science at Roger Williams University in Bristol, R.I., who work together at the Marine Biological Laboratory in Woods Hole, Mass., set out with their students to measure how flexible these animal propulsive structures are, and where they bend.
“Why do animals bend while manmade propulsive systems are rigid?” Costello said. “Propellers don’t bend. Wings on planes don’t bend. Helicopter rotors don’t bend.
“It’s not as if animals couldn’t create rigid structures. They do — shells, bones,” Costello said. “If they’ve opted not to, there’s probably a pretty good reason.”
Animals are much more efficient when it comes to cost per transport — a calculation of energy per unit mass per distance, similar to miles per gallon for vehicles.
“In the range of weights of animals, animals are usually somewhere between 100 and 1,000 times more efficient,” Costello said.
His team took an informatics approach to the question, he said. Just as molecular biologists often rely on vast storehouses of data held in shared banks, “we’re interrogating that vast database of videos that people put on YouTube for whatever reason,” Costello said. “People take videos of a leech in a bucket swimming around and for some reason think it’s worth posting. Well, it’s worth it to us.”
Students are adept at searching the web and finding videos, so “I taught them some rudimentary image analysis and let them go,” he said.
The students sorted through hundreds of videos until they found several examples from 59 different species that span the animal kingdom — insects, bats, birds, fish, and molluscs. The videos had to meet specific criteria. For example, birds had to be facing directly into the camera, fish required a bird’s-eye view, and whales or dolphins had to be viewed from the side. They also had to be moving at a steady speed, rather than taking off or landing.
Students then extracted individual frames from the selections and used image analysis software to measure the bending.
Despite the differences in the animals, they found similarities. The wings of a monarch butterfly bend in a similar location and to an angle similar to the tail of a bottlenose dolphin. This is true despite the fact that flying insects have no muscles in their wings, unlike the other animals studied. And it didn’t matter whether they were flying through the air or swimming in water.
“From a physical fluids basis, they’re just fluids of different densities,” Costello said.
Seven of the paper’s nine authors are PC alumni or researchers, including Wesley T. Beaulieu ’09, a doctoral candidate in biology at Indiana University who is also working on a master’s degree in statistics there. He contributed analysis of phylogenetic signaling. Eric Cathcart ’12, Nathan Johnson ’12, and Gregory Tirrell ’11 were all researchers as undergraduates.
“Students are the engine for a lot of our most novel work,” Costello said.
Johnson, one of the lead authors of the paper, is pursuing a master’s degree in marine biology at Texas A&M University at Galveston. The management major said he was always interested in science, so he planned to minor in biology, but had never considered it as a career. However, after a few courses, he was hooked.
As a junior, he reviewed the research interests of all the biology professors and asked Costello, a marine biologist, if there were any opportunities for research, so he could “get a taste for the field and a sense of what I want to do,” Johnson said.
Costello invited him to read some background papers and, if he was interested, to join the biomechanics project. “When you talk with him, it’s hard not to get excited,” Johnson said.
“A great thing about an undergraduate place like this is that we’ll work with finance majors, and we’ll work with bio majors and work with art majors,” Costello said.
Initially they analyzed still images but later realized they needed data from several cycles of the moving bodies, so they turned to video. They started out using sources such as National Geographic, but ultimately turned to YouTube.
“YouTube is just much easier. You just have to type in whatever you’re looking for,” Johnson said.
The results suggest that all these different animal groups arrived at similar bending patterns through convergent evolution.
“What is it about bending like that that is advantageous or optimal?” Costello said. “With colleagues, we’re testing those kinds of ideas and analyzing in detail.”
By recognizing these patterns, “we should be able to distinguish the mechanical basis for the biological optimum that we’re seeing,” he said. Then those principles can be incorporated into vehicle design.
“Animals have evolved it within their lineages,” Costello said. “We hope we can get there in a few years and shortcut about 300 million years of evolution.”
— Liz F. Kay
Photo credit, whale tail: Michael L. Baird/flickr
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