Why Do Dogs Crouch Forward When They’re Playing?

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Whether they're tilting their heads or exposing their bellies for rubs, dogs are experts at looking adorable. But these behaviors do more than elicit squeals from delighted humans; in many cases, they serve important evolutionary functions. A prime example is the "play bow": If you've ever seen a dog crouch forward with its elbows on the ground and its rear end in the air, wagging tail and all, then you know what it is. The position is the ultimate sign of playfulness, which is important for a species that often uses playtime as practice for attacking prey.

The play bow first evolved in canids as a form of communication. When a dog sees another dog it wants to play with, it extends its front paws forward and lifts up its behind as a visual invitation to engage in a friendly play session. Dogs will "bow" in the middle of playtime to show that they're having fun and wish to continue, or when a session has paused to signal they want to pick it back up. Play bows can also be a sort of apology: When the roughhousing gets too rough, a bow says, “I’m sorry I hurt you. Can we keep playing?”

Play between canines often mimics aggression, and starting off in a submissive position is a way for all participating parties to make sure they’re on the same page. It’s easy to see why such a cue would be useful; the more puzzling matter for researchers is why the ancestors of modern dogs evolved to play in the first place. One theory is that play is crucial to the social, cognitive, and physical development of puppies [PDF]. It’s an opportunity for them to interact with their own kind and learn important behaviors, like how to moderate the strength of their bites. Play also requires the animals to react quickly to new circumstances and assess complex actions from other dogs.

Shiba inus playing outside.
Taro the Shiba Inu, Flickr // CC BY 2.0

Another evolutionary explanation is that playtime prepares puppies for the hunting they do later as adults. Watch two puppies play and you’ll see them stalking, biting, and pouncing on one another—all behaviors canines exhibit in the wild when taking down prey.

Of course, it’s also possible that dogs simply play because it’s fun. This is a strong case for why pet dogs continue to play into adulthood. “Devoting a lot of time to play may be less advantageous for a wild species who spends much of its time hunting or foraging for food, searching for mates, or avoiding predators,” Dr. Emma Grigg, an animal behaviorist and co-author of The Science Behind a Happy Dog, tells Mental Floss. “Many domestic dogs are provisioned by humans, and so have more time and energy to devote to play as adults.”

Because play is a lifelong activity for domestic dogs, owners of dogs of all ages have likely seen the play bow in person. Wild canids, like wolves, foxes, and coyotes, tend to reserve this behavior for members of their own species, but pet dogs often break out the bow for their humans—or anyone else who looks like they might be up for a play session. Grigg says, “One of my dogs regularly play bows to her favorite of our cats.”

Are Any of the Scientific Instruments Left on the Moon By the Apollo Astronauts Still Functional?

Apollo 11 astronaut Neil Armstrong left the first footprint on the Moon on July 20, 1969.
Apollo 11 astronaut Neil Armstrong left the first footprint on the Moon on July 20, 1969.
Heritage Space/Heritage Images/Getty Images

C Stuart Hardwick:

The retroreflectors left as part of the Apollo Lunar Ranging Experiment are still fully functional, though their reflective efficiency has diminished over the years.

This deterioration is actually now delivering valuable data. The deterioration has multiple causes including micrometeorite impacts and dust deposition on the reflector surface, and chemical degradation of the mirror surface on the underside—among other things.

As technology has advanced, ground station sensitivity has been repeatedly upgraded faster than the reflectors have deteriorated. As a result, measurements have gotten better, not worse, and measurements of the degradation itself have, among other things, lent support to the idea that static electric charge gives the moon an ephemeral periodic near-surface pseudo-atmosphere of electrically levitating dust.

No other Apollo experiments on the moon remain functional. All the missions except the first included experiment packages powered by radiothermoelectric generators (RTGs), which operated until they were ordered to shut down on September 30, 1977. This was done to save money, but also because by then the RTGs could no longer power the transmitters or any instruments, and the control room used to maintain contact was needed for other purposes.

Because of fears that some problem might force Apollo 11 to abort back to orbit soon after landing, Apollo 11 deployed a simplified experiment package including a solar-powered seismometer which failed after 21 days.

This post originally appeared on Quora. Click here to view.

What Makes a Hotel Breakfast 'Continental'?

Hotels often offer a complimentary pastry and fruit breakfast.
Hotels often offer a complimentary pastry and fruit breakfast.
tashka2000/iStock via Getty Images

The continental breakfast, which is typically made up of pastries, fruit, and coffee, is often advertised by hotels as a free perk for guests. But why is it called continental, and why don’t patrons get some eggs and bacon along with it?

The term dates back to 19th century Britain, where residents referred to mainland Europe as “the continent.” Breakfast in this region was usually something light, whereas an English or American breakfast incorporated meat, beans, and other “heavy” menu options.

American hotels that wanted to appeal to European travelers began advertising “continental breakfasts” as a kind of flashing neon sign to indicate guests wouldn’t be limited to American breakfast fare that they found unappealing. The strategy was ideal for hotels, which saved money by offering some muffins, fruit, and coffee and calling it a day.

That affordability as well as convenience—pastries and fruit are shelf-stable, requiring no heat or refrigeration to maintain food safety—is a big reason continental breakfasts have endured. It’s also a carryover from the hybrid model of hotel pricing, where American hotels typically folded the cost of meals into one bill and European hotels billed for food separately. By offering a continental breakfast, guests got the best of both worlds. And while Americans were initially aghast at the lack of sausages and pancakes on offer, they’ve since come around to the appeal of a muffin and some orange juice to get their travel day started.

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