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Wolfgang Wander via Wikimedia Commons // CC BY-SA 3.0

Woodpeckers Assess Competitors by Their Drumming Skills

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Wolfgang Wander via Wikimedia Commons // CC BY-SA 3.0

In a recent study, biologists say woodpecker couples decide whether or not they need to defend their territory by assessing other woodpeckers’ drumming abilities. The researchers published their findings in the journal Behavioral Ecology and Sociobiology.

Downy woodpeckers (Picoides pubescens) are small birds that take up a lot of room. Each downy woodpecker couple maintains a territory centered around the tree where they’ve made their nest cavity. These territories are often challenged by lone male newcomers, who then frequently find themselves attacked by two angry birds.

However, some intruders are left alone. Researchers wondered how woodpecker couples determine which birds are worthy of this détente. They suspected that the occupying male and female might decide together after hearing what the new bird can do.

Woodpeckers peck to dig out bugs or to carve out nest cavities into the trunks of trees. But their characteristic jackhammer sound is not from pecking; it’s drumming. Unlike pecking, drumming, which usually takes place on especially loud trees or surfaces, serves a purely social purpose—announcing the presence of the drummer to any potential mates or rivals. And as in the world of human music, some drummers are better than others.

Wake Forest University researchers looking for woodpeckers. Image Credit: WFU/Ken Bennett

The researchers took recording equipment into downy woodpecker territories and recorded intruders’ drumming songs. They then manipulated those songs to make them shorter or longer. They returned to the reigning couples’ territories, played back the songs, and watched to see what the birds would do. They found that longer songs consistently got the birds revved up and ready to fight, as it made them believe there was a strong threat nearby. Meanwhile, shorter drums were more or less ignored. But before each bird acted, it checked to see what its partner was doing.

"Partners will actually coordinate or cooperate with how they fight depending on who they are fighting,” study co-author Matthew Fuxjager said in a press statement. “They size up their opponent and decide whether they need to work together. In short, it means an intruder woodpecker with a short drum is perceived as wimpier, while a long drum signifies a tough guy intruder."

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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