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Rats Save Drowning Pals, Skip the Chocolate

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Many studies have shown that rats exhibit empathy and social behavior. In one, scientists trapped a rat in a tight plastic tube and observed as its free cagemate, distressed by the trapped rat's panicked squirming, maneuvered the latch to free it. But many critics attributed the free rat's behavior to a need for companionship, not sensitivity to a fellow rodent's distress. (Rats get lonely too, you know.)

But a new study published in Animal Cognition (the somewhat awkwardly titled "Rats demonstrate helping behavior toward a soaked conspecific") from Kwansei Gakuin University in Japan shows that a rat's empathy extends to rodents it's not motivated to socialize with. In the study, scientists set up a box with two compartments separated by a transparent wall. A rat was placed in each compartment. One side was filled with water, forcing the rat within to swim. (The rat wasn't at risk of drowning, but it wasn't having any fun either.) Meanwhile, the rat on the dry side witnessed the soaked rat's distress—and then opened a tiny door leading to its dry compartment so the wet rat could escape.  

The dry rats repeatedly saved their struggling buddies. If there was no water in the box at all, the rats didn't open the door, which suggests the rats were motivated by empathy, not a need to socialize. Interestingly, rats that had previously experienced the wet side of the box were more likely to free their friends, showing they were very likely able to empathize.

For a final test, scientists threw a chocolate bribe into the mix. The dry rat now had to choose between two doors: one to the "soaked conspecific," and one to a tasty treat. Fifty to 80 percent of the time, the dry rat chose to save the wet rat. Rats seem to value friendship as much as they do food. 

Scientists believe this behavior is learned, not innate. In another recent study, neurobiologists from the University of Chicago transferred albino rat babies into a black-patched rat group, which raised them. When these albino adoptees grew up, in experiments they would help black-patched rats, but not other albinos. This is further evidence that rats develop relationships based on social familiarity, not biology.  

[h/t: Science Mag]

Watch a School of Humpback Whales 'Fish' Using Nets Made of Bubbles 

Just like humans, humpback whales catch many fish at once by using nets—but instead of being woven from fibers, their nets are made of bubbles.

Unique to humpbacks, the behavior known as bubble-net feeding was recently captured in a dramatic drone video that was created by GoPro and spotted by Smithsonian. The footage features a school of whales swimming off Maskelyne Island in British Columbia, Canada, in pursuit of food. The whales dive down, and a large circle of bubbles forms on the water's surface. Then, the marine mammals burst into the air, like circus animals jumping through a ring, and appear to swallow their meal.

The video offers a phenomenal aerial view of the feeding whales, but it only captures part of the underwater ritual. It begins with the group's leader, who locates schools of fish and krill and homes in on them. Then, it spirals to the water's surface while expelling air from its blowhole. This action creates the bubble ring, which works like a net to contain the prey.

Another whale emits a loud "trumpeting feeding call," which may stun and frighten the fish into forming tighter schools. Then, the rest of the whales herd the fish upwards and burst forth from the water, their mouths open wide to receive the fruits of their labor.

Watch the intricate—and beautiful—feeding process below:

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Big Questions
Why Do Dogs Love to Dig?
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Dog owners with green thumbs beware: It's likely just a matter of time before Fido turns your azalea bed into a graveyard of forgotten chew toys. When dogs aren't digging up your prized garden, they can be found digging elsewhere in your yard, at the beach, and even between your couch cushions at home. But what exactly is behind your dog's drive to turn every soft surface he or she sees into an excavation site?

According to Dr. Emma Grigg, an animal behaviorist and co-author of The Science Behind a Happy Dog, this behavior is completely normal. "When people say 'why do dogs dig,' the first thing that always comes to mind is 'well, because they're dogs,'" she tells Mental Floss. The instinct first appeared in dogs' wolf ancestors, then it was amplified in certain breeds through artificial selection. That's why dogs that were bred to hunt rodents, like beagles and terriers, are especially compelled to dig in places where such animals might make their homes.

But this tendency isn't limited to just a few specific breeds. No matter their original roles, dogs of all breeds have been known to kick up some dirt on occasion. Beyond predatory urges, Dr. Grigg says there are two main reasons a dog may want to dig. The first is to cool off on a hot day. When stuck on an open lawn with little to no shade, unearthing a fresh layer of dirt untouched by the sun is a quick way to beat the heat.

The second reason is to stash away goodies. Imagine your dog gets bored with chewing his favorite bone but knows he wants to come back for it later. Instead of leaving it out in the open where anyone can snatch it up, he decides to bury it in a secret place where only he'll be able to find it. Whether or not he'll actually go back for it is a different story. "There's a disconnect with modern dogs: They know the burying part but they don't always know to dig it up," Dr. Grigg says.

Because digging is part of a dog's DNA, punishing your pet for doing so isn't super effective. But that doesn't mean you should stand idly by as your yard gets turned inside-out. When faced with this behavior in your own dog, one option is to redirect it. This can mean allowing him to dig in a designated corner of the yard while keeping other parts off-limits, or setting up a raised flowerbed or sandbox especially to satisfy that urge. "You can get him interested in the area by burying a couple bones or some interesting things in there for him to dig," Dr. Grigg says. "I like the idea of buried treasure."

If your dog's motive for digging is more destructive than practical, he may have an energy problem. Dogs require a certain amount of stimulation each day, and when their humans don't provide it for them they find their own ways to occupy themselves. Sometimes it's by chewing up shoes, toppling trash cans, or digging ditches the perfect size for twisting ankles. Fortunately, this is nothing more walks and playtime can't improve.

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