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Photo by Stephanie Ware, The Field Museum.

Given the Opportunity to Cheat on Their Mates, City Falcons Stay True

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Photo by Stephanie Ware, The Field Museum.

City life is a singular experience. We cram ourselves into territories far too small to support us and stack our homes on top of one another. We encounter other people at a rate that would have shocked and terrified our ancestors. In order to survive the city’s stresses and compression, we build up, we speed up, and we toughen up. For better or for worse, we change. And the same holds true for other animals. But some things stay the same; experts say that, even in crowded conditions, Chicago’s peregrine falcons stick to their naturally monogamous mating habits. The research was published in the journal PLOS One. 

Scientists have good reason to keep an eye on these birds. Fifty years ago, the widespread use of DDT nearly wiped out the U.S.’s entire population of peregrine falcons (Falco peregrinus). A ban on the pesticide, combined with aggressive conservation programs, have helped the birds bounce back in a major way. But like so many modern humans, the birds have urbanized. In Illinois alone, almost 90 percent of the peregrine falcon parents build their nests on Chicago’s buildings and bridges. This is a big shift for the falcon pairs, who historically maintained large territories around their cliffside nests. In isolated conditions, monogamy might be a natural choice (where would a bird even find someone else?) but the falcons are isolated no longer. Could living in such close proximity to others encourage falcons to sleep around?

To find out, a team of Chicago-based scientists tracked the nesting behavior of 350 birds at 20 nesting sites in nine Midwestern cities; they also ran DNA tests on the chicks. Three-quarters of the samples came from Chicago, perhaps because members of the Chicago Peregrine Program were already banding and taking blood samples from every falcon they could find. The ankle bands allowed observers to identify the inhabitants of each nest. By testing the birds’ blood, the researchers could figure out if a couple’s babies were 100 percent their own, or if one of the parents had been stepping out. 

Analysis of the DNA results and nest-watching revealed that, almost to a bird, the falcons remained loyal to their partners. Out of 126 baby birds, only 2 were being raised by a bird other than their biological parent, and even that was a special case: The male bird had hooked up with the already-pregnant female after his own mate had died. He was a stepdad, not a cuckold.

Co-author John Bates is associate curator of birds at The Field Museum in Chicago. He says that he and his colleagues were a little surprised by the results. “Each spring this population also has migratory peregrines passing through on their way to all parts of Canada, so we didn’t know what we were going to find,” he said in a press statement, "but it turns out that almost all of the mated pairs in the city remain monogamous through the years.”

Even greater than their loyalty to each other was the falcons’ loyalty to their nesting sites. It makes sense; while a partner might die in a collision with a building or a power line, a safe nesting niche is forever.

The researchers plan to continue keeping an eye on the birds. 

“Whenever you have animals living in habitats that have been influenced by human development, you have to wonder how the animals’ life histories will be altered,” says Bates. “It’s important to do studies like this one to see how birds are adapting to living in human environments, so that we can monitor changes through time.”

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Animals
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.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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