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7 Clever Hunting Tricks Used in the Animal Kingdom

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The animal world is full of predators with some impressive tricks up their sleeves.

1. Sun-tracking sharks

Great white sharks are the largest predatory fish in the world, and perhaps the most famous of sharks, thanks to their starring role in the Jaws franchise. But new research suggests these creatures are also quite clever. Scientists from Flinders University in Australia now say white sharks can use the sun’s positioning to their advantage when hunting. On sunny mornings, the sharks strike from the east with the rising sun directly behind them. In the afternoons, they switch directions to approach from the west. “This would suggest that the sharks are capable of tracking the sun, which is quite an impressive feat,” says Dr. Charlie Huveneers, an ecologist who led the research. By putting the sun behind them, the sharks are avoiding glare and making their unlucky prey easier to see. 

2. Bait-fishing green herons

This beautiful bird knows the best way to catch a fish is with a little bait. They’re sometimes observed dropping bits of bait—bread, for example—into the water to lure curious victims to the surface before striking. For other herons, little fish become the bait itself, used to trick bigger fish looking for a meal. Watching a heron fish with such precision and ingenuity is a creepy reminder that birds are actually really smart.

Not to be outdone by its green cousin, the black heron has another smart tactic for finding dinner: it shapes its wings into an "umbrella" that creates shade. This allows it to see down into the water by reducing the sun’s glare, but serves the dual purpose of attracting fish, which are drawn to dark areas of vegetation. You can see this ingenious trap at work here.

3. Color-changing crab spiders

Call them the chameleons of the arachnid world. The female whitebanded crab spider can change its own color from white to yellow and back again to avoid being detected while it waits patiently on flower petals before ambushing prey. Males, sadly, aren't blessed with this talent.

4. Bubble-blowing humpback whales

These giant creatures work together to corral large schools of krill or herring into one place for a massive meal. The whales swim in an upward spiral below the fish and release columns of air bubbles, which the fish won’t swim through, essentially creating a bubble net around the prey. Researchers say this hunting skill is passed on from whale to whale.

5. Sneaky crocodiles

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Mugger crocodiles in India and some American alligators have been observed lying completely still just beneath the surface of the water for long periods of time, their snouts deliberately covered by sticks. It seems these reptiles have learned that, during heron mating season, the birds need sticks to build their nests. By hiding beneath something that’s in high demand, the crocodiles and alligators nearly guarantee themselves a meal if they can wait long enough. “If the crocodylians really are using the sticks as bait to attract their bird prey,” writes Darren Naish at Scientific American, “this is tool use, since the sticks are objects that are being employed for a specific function.”

6. The fish that plays dead

Possums aren’t the only animals that play dead. In East Africa, a species of cichlid fish uses this skill to catch smaller fish for dinner. In shallow waters, the fish sinks to the ground as if dead. Some fish spend up to 15 minutes in this position, waiting for someone to take the bait. Smaller fish, convinced by the act, nibble on the corpse of the cichlid. If they come close enough, the faking fish snaps to life and nabs a meal. But this hunting method comes with a cost: Some cichlid fish sustain lifelong injuries to their fins from essentially using their own bodies as bait.

7. Mimicking jungle cats

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Mimicry is a well-utilized and impressive skill in the animal world. One good example is the morgay, or tree ocelot, in the Amazonian forests of the Reserva Florestal Adolpho Ducke in Brazil. This jungle cat mimics the call of baby pied tamarin monkeys to attract curious adult monkeys. "Cats are known for their physical agility, but this vocal manipulation of prey species indicates a psychological cunning which merits further study," says Wildlife Conservation Society researcher Fabio Rohe.

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iStock // Ekaterina Minaeva
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Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
May 21, 2017
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iStock // Ekaterina Minaeva

Jacques Mattheij made a small, but awesome, mistake. He went on eBay one evening and bid on a bunch of bulk LEGO brick auctions, then went to sleep. Upon waking, he discovered that he was the high bidder on many, and was now the proud owner of two tons of LEGO bricks. (This is about 4400 pounds.) He wrote, "[L]esson 1: if you win almost all bids you are bidding too high."

Mattheij had noticed that bulk, unsorted bricks sell for something like €10/kilogram, whereas sets are roughly €40/kg and rare parts go for up to €100/kg. Much of the value of the bricks is in their sorting. If he could reduce the entropy of these bins of unsorted bricks, he could make a tidy profit. While many people do this work by hand, the problem is enormous—just the kind of challenge for a computer. Mattheij writes:

There are 38000+ shapes and there are 100+ possible shades of color (you can roughly tell how old someone is by asking them what lego colors they remember from their youth).

In the following months, Mattheij built a proof-of-concept sorting system using, of course, LEGO. He broke the problem down into a series of sub-problems (including "feeding LEGO reliably from a hopper is surprisingly hard," one of those facts of nature that will stymie even the best system design). After tinkering with the prototype at length, he expanded the system to a surprisingly complex system of conveyer belts (powered by a home treadmill), various pieces of cabinetry, and "copious quantities of crazy glue."

Here's a video showing the current system running at low speed:

The key part of the system was running the bricks past a camera paired with a computer running a neural net-based image classifier. That allows the computer (when sufficiently trained on brick images) to recognize bricks and thus categorize them by color, shape, or other parameters. Remember that as bricks pass by, they can be in any orientation, can be dirty, can even be stuck to other pieces. So having a flexible software system is key to recognizing—in a fraction of a second—what a given brick is, in order to sort it out. When a match is found, a jet of compressed air pops the piece off the conveyer belt and into a waiting bin.

After much experimentation, Mattheij rewrote the software (several times in fact) to accomplish a variety of basic tasks. At its core, the system takes images from a webcam and feeds them to a neural network to do the classification. Of course, the neural net needs to be "trained" by showing it lots of images, and telling it what those images represent. Mattheij's breakthrough was allowing the machine to effectively train itself, with guidance: Running pieces through allows the system to take its own photos, make a guess, and build on that guess. As long as Mattheij corrects the incorrect guesses, he ends up with a decent (and self-reinforcing) corpus of training data. As the machine continues running, it can rack up more training, allowing it to recognize a broad variety of pieces on the fly.

Here's another video, focusing on how the pieces move on conveyer belts (running at slow speed so puny humans can follow). You can also see the air jets in action:

In an email interview, Mattheij told Mental Floss that the system currently sorts LEGO bricks into more than 50 categories. It can also be run in a color-sorting mode to bin the parts across 12 color groups. (Thus at present you'd likely do a two-pass sort on the bricks: once for shape, then a separate pass for color.) He continues to refine the system, with a focus on making its recognition abilities faster. At some point down the line, he plans to make the software portion open source. You're on your own as far as building conveyer belts, bins, and so forth.

Check out Mattheij's writeup in two parts for more information. It starts with an overview of the story, followed up with a deep dive on the software. He's also tweeting about the project (among other things). And if you look around a bit, you'll find bulk LEGO brick auctions online—it's definitely a thing!

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Name the Author Based on the Character
May 23, 2017
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