CLOSE
Nick Hobgood via Wikimedia Commons // CC BY-SA 3.0
Nick Hobgood via Wikimedia Commons // CC BY-SA 3.0

Coral and Algae Have Been Friends for 212 Million Years

Nick Hobgood via Wikimedia Commons // CC BY-SA 3.0
Nick Hobgood via Wikimedia Commons // CC BY-SA 3.0

Some classics were just made to go together. Peanut butter and chocolate. Thanksgiving dinner and stretch pants. Scleractinian corals and dinoflagellate algae. And boy, do those two go way back—scientists looking at fossils say the two have been cohabiting since at least about 212 million years ago, in the Late Triassic Period. The researchers published their report today in the journal Science Advances.

Happy, healthy coral is essential for a happy, healthy reef. To stay happy and healthy, many modern corals have forged super close relationships with teeny algae called zooxanthellae. The corals give the algae a safe place to live and the chemical components for photosynthesis, while the algae make oxygen, keep the water clean, and produce all kinds of helpful nutrients. The pair really have a good thing going.

But just how long it’s been going on has been anybody’s guess. Previous studies on the pair’s relationship have been largely speculative, using data from modern-day corals to imagine their ancestors’ world.

Now, two new scientific techniques, one visual and one chemical, have allowed us to get a far more accurate picture of coral history.

Earlier this year, lead author Katarzyna Frankowiak and a number of her co-authors reported that they’d figured out how to tell if a fossilized hard coral had been in a relationship with algae. The trick, they said, is to look very closely at the coral’s skeleton to see how it had grown and aged. Even when the algae itself was long gone, its presence had left irrevocable (if microscopic) changes in the coral’s life.

For the new study, the researchers applied this technique to tiny samples of fossilized hard corals found near the former Tethys Sea in Turkey. They used a variety of high-powered microscopes to examine the fossils in the most minute of detail and found that the skeletons of these ancient, ancient samples looked a lot like those of modern symbiotic hard corals.

Algae activity (brown dots in the tissue, upper left image) is recorded in the coral skeleton as structural (growth bands; upper right image) and geochemical signatures. Such regular growth bands occur in Upper Triassic (ca. 220 Ma) scleractinian corals (lower images) as well. Image Credit: Isabelle Domart-Coulon (upper left), Jarosław Stolarski (upper right, and lower images)

The second new method concerned the corals’ chemical composition. The experience of living with algae alters a coral’s very molecules, changing the ratio of various oxygen, carbon, and nitrogen isotopes. And just as with the visual inspection, analysis of the fossil corals’ isotopes suggested that they’d been sharing their lives with zooxanthellae.

Analyzing the coral isotopes yielded another insight: the sea in which these buddies lived was likely in pretty poor condition. The fossil corals shared a similar ratio of nitrogen isotopes with modern symbiotic Bermuda corals, which are currently struggling in nutrient-starved waters. It’s possible, the researchers say, that these difficult conditions were what inspired the algae and the corals to band together in the first place.

nextArticle.image_alt|e
iStock
arrow
Animals
15 Reasons You Should Appreciate Squirrels
iStock
iStock

Even if you live in a big city, you probably see wildlife on a regular basis. Namely, you're sure to run into a lot of squirrels, even in the densest urban areas. And if you happen to live on a college campus, well, you're probably overrun with them. While some people might view them as adorable, others see them as persistent pests bent on chewing on and nesting in everything in sight. But in honor of National Squirrel Appreciation Day, here are 15 reasons you should appreciate the savvy, amazing, bushy-tailed critters.

1. THEY CAN JUMP REALLY, REALLY FAR.

A flying squirrel soars through the air
iStock

In one study [PDF] of the tree-dwelling plantain squirrels that roam the campus of the National University of Singapore, squirrels were observed jumping almost 10 feet at a stretch. In another study with the eastern ground squirrel, one researcher observed a squirrel jumping more than 8 feet between a tree stump and a feeding platform, propelling itself 10 times the length of its body. Flying squirrels, obviously, can traverse much farther distances midair—the northern flying squirrel, for instance, can glide up to 295 feet [PDF].

2. THEY'RE VERY ORGANIZED …

A squirrel digs in a grassy field filled with fallen leaves.
iStock

In fact, they may be more organized than you are. A recent study found that eastern fox squirrels living on UC Berkeley's campus cache their nuts according to type. When given a mixture of walnuts, pecans, almonds, and hazelnuts, the squirrels took the time to hide each type of nut in a specific place. This method of "spatial chunking" may help them remember where the nuts are when they go to retrieve them later. Though the study wasn't able to determine this for sure, the study's results suggested that the squirrels may have been organizing their caches by even more subtle categories, like the size of the nuts.

3. … BUT THEIR FORGETFULNESS HELPS TREES GROW.

Looking up a tree trunk at a squirrel climbing down
iStock

Tree squirrels are one of the most important animals around when it comes to planting forests. Though they may be careful about where they bury their acorns and other nuts, they still forget about quite a few of their caches (or at least neglect to retrieve them). When they do, those acorns often sprout, resulting in more trees—and eventually, yet more acorns for the squirrels.

4. THEY HELP TRUFFLES THRIVE.

A man holds a truffle up for the camera.
iStock

The squirrel digestive system also plays an important role in the survival of truffles. While above-ground mushrooms can spread their spores through the air, truffles grow below ground. Instead of relying on the air, they depend on hungry animals like squirrels to spread their spores to host plants elsewhere. The northern flying squirrel, found in forests across North America, depends largely on the buried fungi to make up its diet, and plays a major role in truffle propagation. The squirrels poop out the spores unharmed on the forest floor, allowing the fungi to take hold and form a symbiotic relationship with the tree roots it's dropped near.

5. THEY'RE ONE OF THE FEW MAMMALS THAT CAN SPRINT DOWN A TREE HEAD-FIRST.

A squirrel stands on the knot of a tree trunk looking down at the ground.
iStock

You may not be too impressed when you see a squirrel running down a tree, but they're actually accomplishing a major feat. Most animals can't climb vertically down head-first, but squirrel's back ankles can rotate 180°, turning their paws all the way around to grip the tree trunk as they descend.

6. SEVERAL TOWNS COMPETE FOR THE TITLE OF 'HOME OF THE WHITE SQUIRREL.'

A white squirrel in Olney, Illinois stands on its hind legs.
iStock

Squirrels are a more popular town mascot than you might think. Surprisingly, more than one town wants to be known as the "home of the white squirrel," including Kenton, Tennessee; Marionville, Missouri; the Canadian city of Exeter, Ontario; and Brevard, North Carolina, the location of the annual White Squirrel Festival. But Olney, Illinois may be the most intense about its high population of albino squirrels. There is a $750 fine for killing the all-white animals, and they have the legal right-of-way on roads. There's an official city count of the squirrels each year, and in 1997, realizing that local cats posed a threat to the beloved rodent residents, the city council banned residents from letting their cats run loose outdoors. In 2002, the city held a 100-Year White Squirrel Celebration, erecting a monument and holding a "squirrel blessing" by a priest. Police officers wore special squirrel-themed patches for the event.

7. THEY CAN AID STROKE RESEARCH.

An illustration of different regions of the brain lighting up in blue
iStock

Ground squirrels hibernate in the winter, and the way their brains function while they do may help scientists develop a new drug that can limit the brain damage caused by strokes. When ground squirrels hibernate, their core body temperature drops dramatically—in the case of the arctic ground squirrel, to as low as 26.7°F, possibly the lowest body temperature of any mammal on Earth. During this extra-cold hibernation, a squirrel's brain undergoes cellular changes that help its brain deal with reduced blood flow. Researchers are currently trying to develop a drug that could mimic that process in the human brain, preventing brain cells from dying when blood flow to the brain is cut off during a stroke.

8. THEIR FUR MAY HAVE SPREAD LEPROSY IN THE MIDDLE AGES.

A woman in a fur vest with a hood faces away from the camera and stares out over the water.
iStock

If you always warn your friends not to pet or feed squirrels because they can spread disease, put this story in your back pocket for later: They may have helped leprosy spread from Scandinavia to the UK in the 9th century. Research published in 2017 found a strain of leprosy similar to a modern variant found in squirrels in southern England in the skull of a woman who lived in England sometime between 885 and 1015 CE. The scientists suggest that the leprosy may have arrived along with Viking squirrel pelts. "It is possible that this strain of leprosy was proliferated in the South East of England by contact with highly prized squirrel pelt and meat, which was traded by the Vikings at the time this woman was alive," one of the authors told The Guardian. That may not be the most uplifting reason to appreciate squirrels, but it's hard not to admire their influence!

9. THEY'RE MORE POWERFUL THAN HACKERS.

A squirrel runs across a power line.
Frederic J. Brown, AFP/Getty Images

While energy companies may worry about hackers disrupting the power grid, squirrels are actually far more powerful than cyber-whizzes when it comes to sabotaging our electricity supply. A website called Cyber Squirrel 1 documents every public record of squirrels and other animals disrupting power services dating back to 1987. It has counted more than 1100 squirrel-related outages across the world for that time period, which is no doubt a vast underestimate. In a 2016 survey of public power utilities, wildlife was the most common cause of power outages, and for most power companies, that tends to mean squirrels.

10. THEY CAN HEAT UP THEIR TAILS TO WARD OFF PREDATORS.

A ground squirrel sits with its mouth open.
David McNew, Getty Images

California ground squirrels have an interesting way of scaring off rattlesnakes. Like cats, their tails puff up when they go on the defense. A squirrel will wave its tail at a rattlesnake to convince the snake that it's a formidable opponent. Surprisingly, they whip their tails at their foes whether it's light or dark outside. Squirrels can control the blood flow to their tails to cool down or keep warm, and they use this to their advantage in a fight, pumping blood into their tails. Even if the rattlesnakes can't see the bushy tails, researchers found in 2007, they can sense the heat coming off them.

11. THEY HELP SCIENTISTS KNOW WHETHER A FOREST IS HEALTHY.

A squirrel runs down a tree trunk toward a pile of leaves.
iStock

Researchers look at tree squirrel populations to measure just how well a forest ecosystem is faring. Because they depend on their forest habitats for seeds, nesting sites, and food storage, the presence and demographics of tree squirrels in an area is a good bellwether for the health of a mature forest. Studying changes in squirrel populations can help experts determine the environmental impact of logging, fires, and other events that alter forest habitats [PDF].

12. THEY CAN LIE.

A squirrel with a bushy tail stands on its hind legs.
iStock

Gray squirrels know how to deceive. They can engage in what's called "tactical deception," a behavior previously only seen in primates, as a study in 2008 found. When they think they're being watched by someone looking to pilfer their cache of food, the researchers discovered, they will pretend to dig a hole as if burying their acorn or nut, but tuck their snack into their mouth and go bury it elsewhere.

13. THEY WERE ONCE AMERICA'S MOST POPULAR PET.

A man in a hat kisses a squirrel on the White House grounds
Harris & Ewing, Library of Congress // Public Domain

Though some states currently ban (or require permits for) keeping squirrels as pets, it was once commonplace. Warren G. Harding kept a squirrel named Pete who would sometimes show up to White House meetings and briefings, where members of Harding's cabinet would bring him nuts. But keeping a squirrel around wasn't just for world leaders—the rodent was the most popular pet in the country, according to Atlas Obscura. From the 1700s onwards, squirrels were a major fixture in the American pet landscape and were sold in pet shops. Despite Harding's love of Pete, by the time he lived in the White House in the 1920s, squirrel ownership was already on the wane, in part due to the rise of exotic animal laws.

14. THE MERE SIGHT OF JUST ONE COULD ONCE ATTRACT A CROWD.

A historical photo of nurses leaning down to feed a black squirrel
Library of Congress // Public Domain

The American cities of the 1800s weren't great places to catch a glimpse of wildlife, squirrels included. In fact, the animals were so rare that in the summer of 1856, when a gray squirrel escaped from its cage inside a downtown New York apartment building (where it was surely living as someone's pet), it merited a write-up in The New York Times. According to the paper, several hundred people gathered to gawk at the tree where the squirrel took refuge and try to coax the rodent down. In the end, a police officer had to force the crowd to disperse. The paper did not document what happened to the poor squirrel.

15. IN THE 19TH CENTURY, THEY WERE TASKED WITH TEACHING COMPASSION.

A boy doing homework with a squirrel on the table.
Hulton Archive, Getty Images

In the mid-1800s, seeking to return a little bit of nature to concrete jungles, cities began re-introducing squirrels to their urban parks. Squirrels provided a rare opportunity for city slickers to see wildlife, but they were also seen as a sort of moral compass for young boys. Observing and feeding urban squirrels was seen as a way to steer boys away from their "tendency toward cruelty," according to University of Pennsylvania historian Etienne Benson [PDF]. Boy Scouts founder Ernest Thompson Seton argued in a 1914 article that cities should introduce "missionary squirrels" to cities so that boys could befriend them. He and other advocates of urban squirrels "saw [them] as opportunities for boys to establish trusting, sympathetic, and paternalistic relationships with animal others," Benson writes.

But young boys weren't the only ones that were thought to benefit from a little squirrel-feeding time. When the animals were first reintroduced to parks in the 19th century, feeding squirrels was considered an act of charity—one accessible even to those people who didn't have the means of showing charity in other realms. "Because of the presence of urban squirrels, even the least powerful members of human society could demonstrate the virtue of charity and display their own moral worth," Benson writes. "Gray squirrels helped reshape the American urban park into a site for the performance of charity and compassion for the weak." Even if you were too poor to provide any sort of charity for someone else, you could at least give back to the squirrels.

BONUS: THEY USED TO HATE TAX SEASON TOO.

A colored lithograph shows men and dogs hunting squirrels in a forest.
Currier and Ives, Library of Congress // Public Domain

Though notably absent from big cities, much of the U.S. was once overrun by squirrels. The large population of gray squirrels in early Ohio caused such widespread crop destruction that people were encouraged—nay, required—to hunt them. In 1807, the Ohio General Assembly demanded that citizens not just pay their regular taxes, but add a few squirrel carcasses on top. According to the Ohio History Connection, taxpayers had to submit a minimum of 10 squirrel scalps to the town clerk each year. Tennessee had similar laws, though that state would let people pay in dead crows if they couldn't rustle up enough squirrels.

nextArticle.image_alt|e
iStock
arrow
Design
Forget Horns: Some Trains in Japan Bark Like Dogs to Scare Away Deer
iStock
iStock

In Japan, growing deer populations are causing friction on the railways. The number of deer hit by trains each year is increasing, so the Railway Technical Research Institute has come up with a novel idea for curbing the problem, according to the BBC. Researchers there are using the sound of barking dogs to scare deer away from danger zones when trains are approaching, preventing train damage, delays, and of course, deer carnage.

It’s not your standard horn. In pilot tests, Japanese researchers have attached speakers that blare out a combination of sounds designed specifically to ward off deer. First, the recording captures the animals’ attention by playing a snorting sound that deer use as an “alarm call” to warn others of danger. Then, the sound of howling dogs drives the deer away from the tracks so the train can pass.

Before this initiative, the problem of deer congregating on train tracks seemed intractable. Despite the best efforts of railways, the animals aren’t deterred by ropes, barriers, flashing lights, or even lion feces meant to repel them. Kintetsu Railway has had some success with ultrasonic waves along its Osaka line, but many rail companies are still struggling to deal with the issue. Deer flock to railroad tracks for the iron filings that pile up on the rails, using the iron as a dietary supplement. (They have also been known to lick chain link fences.)

The new deer-deterring soundtrack is particularly useful because it's relatively low-tech and would be cheap to implement. Unlike the ultrasonic plan, it doesn’t have to be set up in a particular place or require a lot of new equipment. Played through a speaker on the train, it goes wherever the train goes, and can be deployed whenever necessary. One speaker on each train could do the job for a whole railway line.

The researchers found that the recordings they designed could reduce the number of deer sightings near the train tracks by as much as 45 percent during winter nights, which typically see the highest collision rates. According to the BBC, the noises will only be used in unpopulated areas, reducing the possibility that people living near the train tracks will have to endure the sounds of dogs howling every night for the rest of their lives.

Deer aren't the only animals that Japanese railways have sought to protect against the dangers of railroad tracks. In 2015, the Suma Aqualife Park and the West Japan Railway Company teamed up to create tunnels that could serve as safer rail crossings for the turtles that kept getting hit by trains.

[h/t BBC]

SECTIONS

arrow
LIVE SMARTER
More from mental floss studios