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Adria C. LeBoeuf

Ants Communicate by Swapping Spit

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Adria C. LeBoeuf

Some insects’ mouth-to-mouth exchanges transmit tiny molecules of hormones and other important chemical information, according to scientists writing in the journal eLife.

The spit-swapping behavior is called trophallaxis. Many entomologists who witnessed the behavior in ants and other social insects believed the bugs were using it to efficiently share food. But some researchers noticed that carpenter ants were trophallax-ing in non-dining contexts, like when one ant would return to its family after being away. The scientists wondered if the ants’ kissing juice contained more than just calories.

They brought lots of ants into the lab to sample what the ants were sharing. At first, the researchers tried just waiting around until one ant initiated trophallaxis, but that mostly resulted in a lot of waiting and very little fluid. Eventually, they figured out that they could gently squeeze the ants’ bellies until the liquid came dribbling out of their mouths.

The researchers ran chemical and genetic tests on the fluid to determine its contents, and they found all kinds of interesting things. The liquid did indeed include particles of food and digestive enzymes, but it also contained several growth-related proteins and a juvenile hormone that can influence an insect’s development.

To find out how these compounds might affect a trophallaxis recipient, the researchers added the juvenile hormone to the meals they were feeding adult ants. The adults passed the hormone-charged liquid onto their larvae. The larvae loved it. Individuals who had taken in the hormone were twice as likely as others to survive to adulthood.

First author Adria LeBoeuf works at the Center for Integrative Genomics in Switzerland. She says the ants could very well be using trophallaxis to decide which larvae succeed. “When the ants feed their larvae, they aren’t just feeding them food, they are casting quantitative ballots for their colony, administering different amounts of growth-promoting components to influence the next generation,” she said in a statement.

Larvae chosen to receive the liquid are being nourished in more ways than one. In some ways, LeBoeuf says, it’s a lot like mammals’ milk. It also suggests that “…the oral exchange of fluids, such as saliva, in other animals might also serve previously unexpected roles." Yum.

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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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Yani Dubin via Flickr Creative Commons // CC BY-ND 2.0
Bumblebees Mark Their Trails With Tiny Scented "Footprints"
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Yani Dubin via Flickr Creative Commons // CC BY-ND 2.0

Bees seem to have an endless number of tricks up their sleeve—and on their feet. Scientists have discovered that bumblebees leave itty-bitty scented “footprints” on every flower they visit, thereby informing other foragers that the bloom’s been recently tapped. The researchers published their findings in the journal Nature Scientific Reports.

Bees are the queens of complex communication. They exchange information with one another and their environments using a dazzling array of sensory input, including electrical impulses, sound, dance, and chemical signals.

Some of those signals flow out into the world through the bees’ delicate little feet. The bottom segment of a bee’s leg, called the tarsus, secretes a scented goo that helps the bee stick to the soft surfaces of flower petals. The chemical profile of each bee’s foot-glue is as unique as a fingerprint.

Previous studies have shown that bees glean important information from one another’s goo, skipping flowers that other bees have already visited. This raised an interesting question: If a bee can "read" another bee’s scent mark, can it also identify that bee?

To find out, researchers planted small clusters of fake flowers in the laboratory and topped some of them up them with sucrose nectar. They then gave bumblebees (Bombus terrestris) free rein to tromp around the blossoms, marking them up and taking in the marks of other bees that had come before.

The bees proved careful and canny readers. Not only did they use other bees’ scent marks to decide which flowers to probe, but they also considered the source of the scent when making that decision. An individual bee could easily differentiate between the smell of its own feet (trustworthy), those of its family members (very trustworthy), and those of strangers (not a reliable source of floral information).

Lead author Richard Pearce is a biologist at the University of Bristol. "Bumblebees are flexible learners and, as we have discovered, can detect whether or not it is they or a different bumblebee that has visited a flower recently. These impressive abilities allows them to be cleverer in their search for food, which will help them to be more successful," he said in a statement.

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