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Study Shows Some Worker Ants Don’t Work At All

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Last summer, researchers at the University of Illinois revealed that most bees aren’t as busy as we give them credit for, and a small group of workers handles the bulk of the labor in a hive. Now, another research team has taken the famously industrious ant down a peg, showing that many ants don’t do their fair share of work—or any work at all.

In many types of social insect, entomologists have found workers that really don’t do much. In some cases, researchers report that half or more of the bugs in a colony are inactive and spend their time just hanging around. Daniel Charbonneau and Anna Dornhaus are biologists at the University of Arizona’s Social Insect Lab, where they primarily study Temnothorax rugatulus, a species of ant found throughout the Western U.S. and Canada. They’ve seen plenty of lazy ants first-hand during their research, but it wasn’t clear whether these ants were consistently inactive or simply taking a break or working in shifts. In a new study, the pair shows that these ants are dedicated to being bums, and that might actually be their job.

The scientists collected five colonies of the ants around Tucson and, using a microscope and thin wire, painstakingly marked 250 workers with unique combinations of paint spots so they could be identified and tracked. They let the ants go about their business for three weeks and recorded them on video for a few minutes at regular intervals. They then went through their footage and recorded what each of the tagged ants was doing.

They found that around 25 percent of the ants were inactive throughout the study. Differences in rest schedules and work shifts didn’t explain the difference, because no matter what time the videos were taken, the same ants were still standing around. These ants were so consistent at doing nothing, the researchers say, that it looks like some workers “effectively specialize in ‘inactivity’” the same way others specialize in foraging for food or tending to the colony’s larvae.

Why do so many ants dedicate themselves to doing so little? Charbonneau and Dornhaus’ study didn’t try to figure that out, but they suggest plenty of ideas that can be tested. First, they say, the inactive ants may have a job to do that they just didn’t see during their short window of ant-watching, maybe a task that’s only performed at a certain time of year or at a specific point in the ants’ life cycle. These particular ants could have also been too young to start working, or too old to continue working and were living the easy life of insect retirement.

They might also be a kind of reserve work force that springs into action when other workers die or the workload in the colony suddenly increases, though other studies testing that idea with different insects found little support for it and showed that when more labor is needed, the ants that are already working just work harder and increase their activity.

Another possibility is that the lazy ants are “behaviorally idle” but not “functionally idle,” and have jobs that don’t require much movement or look like work, such as acting as live feeding stations and regurgitating food for other ants when needed, or relaying chemical messages around the nest.

Finally, the researchers say these ants might just be selfish, shirking their assigned duties so they can conserve energy and minimize their exposure to danger.

“Ultimately, the question of why colonies would produce so many inactive workers, in spite of potentially high production and maintenance costs, is still very much a mystery,” the scientists write, one that will be solved only with more experiments testing all these ideas and others. For now, they urge other ant researchers to not write inactive ants off as inefficient or unimportant just because they don’t do active tasks. Lazy ants are a distinct group with their own unique set of behaviors and characteristics, they write, and ignoring them and their main “activity” in certain studies may skew our understanding of ants’ social structure and division of labor.

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Big Questions
Why Do Cats Love Scratching Furniture?
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Allergy suffering aside, cat ownership has proven health benefits. A feline friend can aid in the grieving process, reduce anxiety, and offer companionship.

The con in the cat column? They have no reservations about turning your furniture into shredded pleather. No matter how expensive your living room set, these furry troublemakers will treat it with the respect accorded to a college futon. Do cats do this out of some kind of spite? Are they conspiring with Raymour & Flanigan to get you to keep updating home decor?

Neither. According to cat behaviorists, cats gravitate toward scratching furniture mostly because that love seat is in a really conspicuous area [PDF]. As a result, cats want to send a message to any other animal that may happen by: namely, that this plush seating belongs to the cat who marked it. Scratching provides both visual evidence (claw marks) as well as a scent marker. Cat paws have scent glands that can leave smells that are detectable to other cats and animals.

But it’s not just territorial: Cats also scratch to remove sloughed-off nail tips, allowing fresh nail growth to occur. And they can work out their knotted back muscles—cramped from sleeping 16 hours a day, no doubt—by kneading the soft foam of a sectional.

If you want to dissuade your cat from such behavior, purchasing a scratching post is a good start. Make sure it’s non-carpeted—their nails can get caught on the fibers—and tall enough to allow for a good stretch. Most importantly, put it near furniture so cats can mark their hangout in high-traffic areas. A good post might be a little more expensive, but will likely result in fewer trips to Ethan Allen.

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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Animals
7 Fun Facts for Elephant Appreciation Day
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Happy Elephant Appreciation Day! Celebrate the occasion with some facts about everyone's favorite gentle giant. 

1. ELEPHANTS CAN RECOGNIZE OTHER ELEPHANT CARCASSES.

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The University of Sussex's Karen McComb told National Geographic that elephants "become excited and agitated if they come across a dead elephant," and, in particular, will investigate skulls and tusks. McComb teamed up with researchers at the Amboseli Elephant Research Project in Kenya to study the behavior, showing wild elephants a range of objects that included skulls. They found that the elephants examined skulls—and tusks in particular—of their own kind twice as long as other skulls, and examined tusks six times as long as they did pieces of wood. They were even able to recognize elephant skulls with the tusks removed, but didn't show preference for certain elephant skulls over others, which suggests they didn't know which skulls belonged to their own relatives. "Animals that are intensely social in life may be most likely to display an interest in their dead," McComb told National Geographic. "But what goes on in their minds while they are doing this is a total mystery."

2. THEY'RE SCARED OF BEES.

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Forget about mice scaring off elephants: When farmers need to keep elephants away from their crops, they should use bees. Researchers in Kenya discovered that even the recorded sound of buzzing bees was enough to make elephants retreat—and cause them to emit a low-frequency sound, inaudible to humans, that warns other elephants of the bees' presence.

"It's impossible to cover Africa in electric fences," Lucy King, author of the paper, told The Huffington Post. "The infrastructure doesn't exist in many places and it would restrict animals' movement." But something like a bee fence—hives strung on strong wires a certain distance apart that would move when elephants walked into them, disturbing the hives—"could be a better way to direct elephants away from farmers' crops," she said.

3. THEY MIGHT UNDERSTAND POINTING.

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Humans often use pointing as a way to nonverbally get a message across, though not many other animals grasp the concept. But according to a two-month study of 11 tame African elephants, these pachyderms might be able to: When presented with two identical buckets and pointed in the direction of the one containing food, elephants picked up on the cue fairly consistently: Elephants had a success rate of 67.5 percent (1-year-old humans have a success rate of 72.7 percent). But an earlier study of Asian elephants indicated that they don’t notice pointing gestures, which is a bit of a mystery.

4. ONE ELEPHANT CAN "TALK." 

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Koshik, an elephant in a South Korean zoo, developed the ability to imitate the sounds of five words he's heard from his trainer—annyeong (hello), anja (sit down), aniya (no), nuwo (lie down), and joa (good)—by sticking his trunk in his mouth. The scientists who first noticed Koshik’s ability speculate that he learned to “talk” because he was lonely.

5. THEY'RE DIGITIGRADES.

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It's Latin for "finger walking," and what it means is that elephants walk on their toes (there are five of them, as well a sixth false toe). According to the book Mammal Anatomy: An Illustrated Guidemost of the animals' weight "rests on a broad pad of elastic tissue behind the toes" which "acts as a shock absorber and prevents the skeleton from jolting too much when the animals walk. It also allows elephants to move surprisingly quietly despite their size."

6. AN ELEPHANT PREGNANCY LASTS ABOUT TWO YEARS.

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If you thought being pregnant for nine months was a long time, be glad you're not an elephant, which can be pregnant for up to 680 days, according to the BBC. All that time in the oven has a benefit, though: Elephant calves are born with highly-developed brains, capable of learning their herd's complex social structures and ready to put their trunks to use.

7. NINETY-SIX ELEPHANTS ARE KILLED IN AFRICA EVERY DAY.

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Unfortunately, elephant poaching remains a very big problem: An estimated 35,000 elephants are killed annually, their tusks sold illegally in the ivory market. Do the math, and that comes out to nearly 96 elephants every day. Find out what you can do to help elephants and stop poaching at 96Elephants.org.

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