Why Do Bats Hang Upside Down?

iStock.com/CraigRJD
iStock.com/CraigRJD

Stefan Pociask:

The age-old question of upside down bats. Yes, it is awfully weird that there is an animal—a mammal even—that hangs upside down. Sure, some monkeys do it when they're just monkeying around. And a few other tree climbers, like margays, hang upside down if they are reaching for something or—again, like the margay cat—may actually even hunt that way ... But bats are the only animals that actually spend most of their time hanging upside down: feeding this way, raising their young this way, and, yes, sleeping or roosting this way.

There is actually a very good and sensible reason why they do this: They have to hang upside down so that they can fly.

First off, we have to acknowledge that bats are not birds, nor are they insects. These are the other two animals that have true powered flight (as opposed to gliding). The difference between bat flight and bird or insect flight is weight—specifically, the ratio of weight to lift-capacity of the wings. If you walk up to a bird or insect, most species will be able to fly right up into the air from a motionless position, and do it quickly.

Bats, on the other hand (or, other wing), can’t do that. They have a lot of difficulty taking off from the ground (not that they can’t do it ... it’s just more difficult). Insects and birds often actually jump into the air to give them a start in the right direction, then their powerful wings take them up, up, and away.

Birds have hollow bones; bats don’t. Insects are made of lightweight chitin or soft, light tissue; bats aren’t. And bats don’t have what you could call "powerful" wings. These amazing creatures are mammals, after all. The only flying mammals. Nature found a way to evolve such an unlikely thing as a flying mammal, so some compromises had to be made. Bats, once airborne, manage perfectly well in the air, and can literally fly circles around most birds in flight. The problem is in first getting off the ground.

To compensate for the extra weight that mammals must have, to compensate for the problem of getting off the ground, evolution found another way for bats to transition from being motionless to immediately being able to fly when necessary. Evolution said, “How about if we drop them from above? That way they are immediately in the air, and all they need to do is start flapping."

It was a great idea, as it turns out. Except bat feet aren’t any good for perching on a branch. They are mammals, not birds, so their musculature, their bones, and their tendons are set up in a completely different way. When a bird squats down on a branch, their tendons actually lock their toes into an even tighter grip on the perch. It happens automatically. That’s part of being a bird, and is universal. That’s why they don’t fall off in their sleep.

Bats, as mammals, are set up differently. Therefore, to compensate for that fact, nature said, “How about if we have them hang upside down? That way, their tendons will actually pull their toes closed, just like a bird does from the opposite direction.” So that’s what evolved. Bats hang from the bottom of something, and all they have to do is "let go" and they are instantly flying. In fact, with this gravity-assist method, they can achieve instant flight even faster than birds, who have to work against gravity.

Side note: In case you were wondering how bats poop and pee while upside down ... First off, pooping is no big deal. Bat poop looks like tiny grains of rice; if they are hanging, it just falls to the floor of the bat cave as guano. Pee, however ... well, they have that covered too. They just “hold it” until they are flying.

So there you go. Bats sleep hanging upside down because they are mammals and can’t take off into the air like birds can (at least not without difficulty). But, if they're hanging, all they do is let go.

Makes total sense, right?

Now, having said all that about upside down bats, I must mention the following: Not all of the 1240-plus species of bats do hang upside down. There are exceptions—about six of them, within two different families. One is in South America (Thyropteridae) and the other is in Madagascar (Myzopodidae). The Myzopodidae, which includes just one species, is exceedingly rare.

So it turns out that these bats roost inside the tubes of young, unfurled banana leaves and other similar large leaves. When they attach themselves to the inside of this rolled leaf, they do it head-up. The problem with living inside of rolled-up leaves is that within a few days, these leaves will continue growing, and eventually open up. Whenever that happens, the whole group of bats has to pick up and move to another home. Over and over again. All six of these species of rare bats have a suction cup on each wrist and ankle, and they use these to attach to the smooth surface of the inside of the leaf tube. Evolution: the more you learn, the more amazing it becomes.

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

Where Did the Term Brownie Points Come From?

bhofack2/iStock via Getty Images
bhofack2/iStock via Getty Images

In a Los Angeles Times column published on March 15, 1951, writer Marvin Miles observed a peculiar phrase spreading throughout his circle of friends and the social scene at large. While standing in an elevator, he overheard the man next to him lamenting “lost brownie points.” Later, in a bar, a friend of Miles's who had stayed out too late said he would never “catch up” on his brownie points.

Miles was perplexed. “What esoteric cult was this that immersed men in pixie mathematics?” he wrote. It was, his colleagues explained, a way of keeping “score” with their spouses, of tallying the goodwill they had accrued with the “little woman.”

Over the decades, the phrase brownie points has become synonymous with currying favor, often with authority figures such as teachers or employers. So where exactly did the term come from, and what happens when you “earn” them?

The most pervasive explanation is that the phrase originated with the Brownies, a subsect of the Girl Scouts who were encouraged to perform good deeds in their communities. The Brownies were often too young to be official Girl Scouts and were sometimes the siblings of older members. Originally called Rosebuds in the UK, they were renamed Brownies when the first troops were being organized in 1916. Sir Robert Baden-Powell, who had formed the Boy Scouts and was asked to name this new Girl Scout division, dubbed them Brownies after the magical creatures of Scottish folklore that materialized to selflessly help with household chores.

But the Brownies are not the only potential source. In the 1930s, kids who signed up to deliver magazines like The Saturday Evening Post and Ladies' Home Journal from Curtis Publishing were eligible for vouchers labeled greenies and brownies that they could redeem for merchandise. They were not explicitly dubbed brownie points, but it’s not hard to imagine kids applying a points system to the brownies they earned.

The term could also have been the result of wartime rationing in the 1940s, where red and brown ration points could be redeemed for meats.

The phrase didn’t really seem to pick up steam until Miles's column was published. In this context, the married men speaking to Miles believed brownie points could be collected by husbands who remembered birthdays and anniversaries, stopped to pick up the dry cleaning, mailed letters, and didn’t spend long nights in pubs speaking to newspaper columnists. The goal, these husbands explained, was never to get ahead; they merely wanted to be considered somewhat respectable in the eyes of their wives.

Later, possibly as a result of its usage in print, grade school students took the phrase to mean an unnecessary devotion to teachers in order to win them over. At a family and faculty meeting at Leon High in Tallahassee, Florida, in 1956, earning brownie points was said to be a serious problem. Also called apple polishing, it prompted other students in class to shame their peers for being friendly to teachers. As a result, some were “reluctant to be civil” for fear they would be harassed for sucking up.

In the decades since that time, the idiom has become attached to any act where goodwill can be expected in return, particularly if it’s from someone in a position to reward the act with good grades or a promotion. As for Miles: the columnist declared his understanding of brownie points came only after a long night of investigation. Arriving home late, he said, rendered him “pointless.”

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

Grocery Stores vs. Supermarkets: What’s the Difference?

gpointstudio/iStock via Getty Images
gpointstudio/iStock via Getty Images

These days, people across the country are constantly engaging in regional term debates like soda versus pop and fireflies versus lightning bugs. Since these inconsistencies are so common, you might have thought the only difference between a grocery store and a supermarket was whether the person who mentioned one was from Ohio or Texas. In reality, there are distinctions between the stores themselves.

To start, grocery stores have been around for much longer than supermarkets. Back when every town had a bakery, a butcher shop, a greengrocery, and more, the grocery store offered townspeople an efficient shopping experience with myriad food products in one place. John Stranger, vice president group supervisor of the food-related creative agency EvansHardy+Young, explained to Reader’s Digest that the grocer would usually collect the goods for the patron, too. This process might sound familiar if you’ve watched old films or television shows, in which characters often just hand over their shopping lists to the person behind the counter. While our grocery store runs may not be quite so personal today, the contents of grocery stores remain relatively similar: Food, drinks, and some household products.

Supermarkets, on the other hand, have taken the idea of a one-stop shop to another level, carrying a much more expansive array of foodstuffs as well as home goods, clothing, baby products, and even appliances. This is where it gets a little tricky—because supermarkets carry many of the same products as superstores, the next biggest fish in the food store chain, which are also sometimes referred to as hypermarkets.

According to The Houston Chronicle, supermarkets and superstores both order inventory in bulk and usually belong to large chains, whereas grocery stores order products on an as-needed basis and are often independently owned. Superstores, however, are significantly larger than either grocery stores or supermarkets, and they typically look more like warehouses. It’s not an exact science, and some people might have conflicting opinions about how to categorize specific stores. For example, Walmart has a line of Walmart Neighborhood Markets, which its website describes as “smaller-footprint option[s] for communities in need of a pharmacy, affordable groceries, and merchandise.” They’re not independently owned, but they do sound like grocery stores, especially compared to Walmart’s everything-under-the-sun superstore model.

Knowing the correct store terms might not always matter in casual conversation, but it could affect your credit card rewards earnings. American Express, for example, offers additional rewards on supermarket purchases, and it has a specific list of stores that qualify as supermarkets, including Gristedes, Shoprite, Stop & Shop, and Whole Foods. Target and Walmart, on the other hand, are both considered superstores, so you won’t earn bonuses on those purchases.

And, since grocery shopping at any type of store can sometimes seem like a competitive sport, here’s the ideal time to go.

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

SECTIONS

arrow
LIVE SMARTER