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15 Shucking Amazing Facts About Oysters

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Oysters are slimy, yet delicious. Casanova purportedly ate 50 of them for breakfast daily—and he isn’t the only one who believed they had certain powers. Oysters are definitely key to healthy marine ecosystems and clean water. Here are 15 facts about these ugly yet amazing shellfish.

1. THEY'RE BETTER WATER FILTERS THAN BRITA BY FAR.

Every day, one oyster filters 50 gallons of water and a healthy one-acre reef around 24 million gallons—enough to fill 36 Olympic swimming pools. Here’s how that works. An oyster draws water in over its gills using cilia, or tiny hairs. Plankton and particles in the water are trapped in mucus in the gill, then transported to the oyster’s mouth. So, yeah, oysters basically eat their own snot but, at the same time, remove excess sediment, nutrients, and algae from the water. That keeps the water in good shape for other marine life.

2. THEY DEVELOP NEIGHBORHOOD COMMUNITIES.

A close-up image of a Gulf Coast oyster bed taken in 2007 for a federal ecosystem restoration initiative. Image credit: EPA via Wikipedia Commons // Public Domain 

Oysters form beds or reefs that provide important habitat for fish and other creatures, including sea anemones and barnacles, which in turn provide food for bigger fish such as striped bass, black drum, and croaker. That works out to 1.5 extra tons of seafood a year.

3. SPRING IS WHEN A YOUNG OYSTER LOOKS FOR LOVE.

Oysters spawn when water temperatures rise in spring. Females release millions of eggs and males even more sperm and some of these lucky gametes meet in the open water. Fertilized eggs develop into microscopic larvae, little more than tiny black specks, which feed on algae, drifting on currents and tides for three weeks. Then, if something else hasn’t eaten them, the larvae attach to a hard surface, most likely other oysters, and transform into a tiny oyster called a spat. In areas where reefs have declined, oyster larvae may never find a place to settle.

4. THEY HOLD BACK FIERCE WAVES. 

Oyster reefs provide an effective natural barrier to storm waves and sea level rise. They absorb as much as 76 to 93 percent of wave energy, which reduces erosion, flooding, and property damage from coastal storms. Oyster reefs are preferable to manmade rip-rap or bulkheads, which don’t provide other benefits, such as habitat, and cost a lot to maintain. According to a Mississippi-Alabama Sea Grant Consortium report, 100 miles of oyster reefs could save up to $95 million on rip-rap or $150 million on bulkheads.

5. FORGET THE 'R' POLICY—OYSTERS ARE GOOD FOR YOU YEAR-ROUND.

Oysters are high in zinc, which is good for your immune system, and also provide calcium, vitamin C, omega 3 fatty acids, iron, and protein. Jason Hedlund, seafood coordinator for Whole Foods Markets, told mental_floss that oysters are low in cholesterol as well. “And that old rule about only eating oysters in months with an ‘R’ in them no longer applies, thanks to developments in food safety,” he added. 

6. IRRITATION LEADS TO BEAUTY AND VALUE.

Not an accurate representation of how pearls are found in oysters. Image credit: iStock

Closely related to the food oysters (family Ostreidae) are the pearl oysters (family Aviculidae). When any small irritant such as a grain of sand gets inside an oyster shell, the animal covers it with nacre, or mother-of-pearl, the substance that forms the inside lining of the shell. Over several years, as more layers are added, a pearl forms. The type, color and shape of a pearl depend on pigment in the nacre and the shape of the original irritant. Today, most pearls are cultured, or created in farmed oysters. Cultured pearls look just like natural ones but are considered less valuable.

7. BAD NEWS: OYSTER REEFS ARE GREATLY IMPERILED WORLDWIDE.

Oyster reefs are the single most imperiled marine habitat on Earth, with 85 to 90 percent of wild reefs lost. The main culprit is destructive fishing practices, including overharvesting, according to a report from The Nature Conservancy, along with habitat loss and declining water quality.

8. GOOD NEWS: REEF RESTORATION WORKS.

Fortunately, oyster reef restoration efforts are very successful. Some 80 restoration projects are currently underway around the U.S., including Nature Conservancy projects in Texas, Louisiana, Mississippi, Alabama, Florida, Georgia, South Carolina, and North Carolina.  Monitoring of these projects has shown as much as 212 percent increases in oyster growth and 850 percent increases in other marine life on the reefs. NOAA is involved in oyster reef restoration in Chesapeake Bay, where native populations had plunged to 1 percent of historic levels.

A study in the Journal of Applied Ecology reviewed literature on the increase in juvenile fish and mobile crustaceans in Crassostrea virginica reefs in the US and found increased production for 19 and 12 species, respectively, in the Gulf of Mexico and in the South and Mid-Atlantic.

9. WE CAN GET CREATIVE WITH REPAIRING THEIR HOMES.  

Marsh grass and oyster beds. Image credit: Steve Hillebrand, U.S. Fish and Wildlife Service, via Wikimedia Commons // Public Domain

A variety of techniques work for oyster reef restoration, from shooting oyster shell from high-pressure hoses to placing bags of shells in the water. Some projects have built lines of shell and rock to stabilize the shoreline along with planting sea grass behind the reef to provide additional habitat. In areas without existing structure for "spat set" (a good location for young oysters, a.k.a. spat), seed oysters from hatcheries are used to establish new reefs.

10. OYSTERS DON'T HAVE FUN ON ACID.

As the oceans absorb more carbon dioxide, it changes the chemistry of the water. The world’s oceans have become 30 percent more acidic since the start of the Industrial Revolution, and that can kill oyster larvae and make it harder for oysters to form shells. 

11. HARVESTING OYSTERS THE RIGHT WAY DOESN'T HARM OTHER SPECIES.

The Monterey Bay Aquarium Seafood Watch rates Eastern oysters from Alabama, Louisiana, Mississippi, Texas, and Florida caught by dredge or tong as "Best Choices." The oyster harvest has no bycatch—other species of marine life caught along with the intended target. Seafood Watch recommendations “help you choose seafood that’s fished or farmed in ways that have less impact on the environment,” according to the organization.

12. THERE ARE FIVE SPECIES IN U.S. WATERS.

A 1910 map of public oyster beds in Virginia's James River. Image credit: Wikimedia Commons // Public Domain

Oysters are found on the East, West, and Gulf Coasts of the US. Crassostrea virginica, the Eastern oyster, ranges from Canada to Key Biscayne, Florida, and throughout the Gulf of Mexico. Ostreola conchaphila is native to the West Coast, where farmed reefs also contain the widely cultivated Pacific or Japanese oyster, Crassostrea gigas. Two more oysters are grown for specialty markets: the European Flat oysters (Ostrea edulis) and Kumamatos (Crassostrea sikamea).

13. ALL YOU NEED IS THE RIGHT KNIFE. OR BACON.

Raw, grilled, fried, wrapped in bacon, mixed into dressing, in soup, casserole or stew—oysters can be eaten just about any way you can think of. Whole Foods seafood coordinator Jason Hedlund calls them a hyper-local seafood, telling mental_floss, “Oysters reflect the bay they come from, almost like a terroir.” Anyone with the right knife and gloves can shuck their own oysters. Watch this video with George Hastings, a national oyster shucking champion (yes, there is such a thing). 

14. OIL IS LETHAL TO OYSTERS AT ALL STAGES OF LIFE.

Oyster production in the Gulf of Mexico declined each of the four years following the BP oil spill disaster. A report from the National Wildlife Federation, Five Years and Counting, states “…oyster eggs, sperm and larvae were exposed to oil and dispersants during the 2010 oil spill. [Polycyclic aromatic hydrocarbons] can be lethal to oyster gametes, embryos, larvae, juveniles and adults. They can also have sub-lethal effects, such as reduced reproductive success.” Unable to move away from such contamination, sedentary oysters are particularly susceptible.

15. SORRY, YOU'RE GOING TO HAVE TO RELY ON YOUR CHARM.

There is little, if any, truth to the idea that oysters are an aphrodisiac. They contain phosphorus and iodine, which may increase human stamina, and zinc aids in production of testosterone. American and Italian researchers found that a type of mussel related to oysters contains two rare amino acids: D-aspartic acid and N-methyl-D-aspartate, which have been shown to increase sperm motility and stimulate testosterone in mice. But no studies have looked at whether that translates to increased libido. As one of the researchers, George Fisher, professor of chemistry at Barry University, told mental_floss, “To my knowledge, the old-wives tale of eating oysters to improve libido has no sustainable, scientific proof.”

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These Sparrows Have Been Singing the Same Songs for 1500 Years
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Swamp sparrows are creatures of habit—so much so that they’ve been chirping out the same few tunes for more than 1500 years, Science magazine reports.

These findings, published in the journal Nature Communications, resulted from an analysis of the songs of 615 adult male swamp sparrows found in six different areas of the northeastern U.S. Researchers learned that young swamp sparrows pick up these songs from the adults around them and are able to mimic the notes with astounding accuracy.

Here’s what one of their songs sounds like:

“We were able to show that swamp sparrows very rarely make mistakes when they learn their songs, and they don't just learn songs at random; they pick up commoner songs rather than rarer songs,” Robert Lachlan, a biologist at London’s Queen Mary University and the study’s lead author, tells National Geographic.

Put differently, the birds don’t mimic every song their elders crank out. Instead, they memorize the ones they hear most often, and scientists say this form of “conformist bias” was previously thought to be a uniquely human behavior.

Using acoustic analysis software, researchers broke down each individual note of the sparrows’ songs—160 different syllables in total—and discovered that only 2 percent of sparrows deviated from the norm. They then used a statistical method to determine how the songs would have evolved over time. With recordings from 2009 and the 1970s, they were able to estimate that the oldest swamp sparrow songs date back 1537 years on average.

The swamp sparrow’s dedication to accuracy sets the species apart from other songbirds, according to researchers. “Among songbirds, it is clear that some species of birds learn precisely, such as swamp sparrows, while others rarely learn all parts of a demonstrator’s song precisely,” they write.

According to the Audubon Guide to North American Birds, swamp sparrows are similar to other sparrows, like the Lincoln’s sparrow, song sparrow, and chipping sparrow. They’re frequently found in marshes throughout the Northeast and Midwest, as well as much of Canada. They’re known for their piercing call notes and may respond to birders who make loud squeaking sounds in their habitat.

[h/t Science magazine]

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16 Playful Facts About Otters
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These adorable aquatic mammals are clever, chatty, and oddly aromatic.

1. THERE ARE 13 SPECIES OF OTTERS, AND JUST ABOUT ALL OF THEM ARE DECREASING.

Only one otter species seems to be thriving, and that's the North American River Otter. The other 12 otter species were recently identified by the International Union for Conservation of Nature (IUCN) as having decreasing populations, and five otter species are already on the endangered list. Among the endangered are the sea otters along the California coast, which are threatened by "environmental pollutants and disease agents." Others, like the marine otters of South America, have had their numbers reduced because of poaching, as well as environmental concerns.

2. ZOROASTRIANS THOUGHT THE OTTERS TO BE NEARLY SACRED CREATURES.

This ancient monotheistic religion considered otters to be the dogs of the river or sea and had strict rules forbidding the killing of otters. It was thought that otters helped keep water purified by eating already dead creatures that might contaminate the water source if they were allowed rot. They would also hold ceremonies for otters found dead in the wild.

3. OTTERS HAVE VERY DISTINCTIVE POOP, AND THAT SCAT HAS ITS OWN NAME.

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Otters use their dung—known as spraint—to mark territory and communicate with other otters. The mammals like to keep things organized within their communities and will designate certain areas to be used as latrines. Spraint scents can vary, but often are (relatively) pleasant—one expert described them as not "dissimilar to jasmine tea." Spraint composition is unique to each otter, and the creatures can identify each other by the smells. Scientists suspect otters may even be able to determine the sex, age, and reproductive status of the spraint dropper just from a quick whiff. And since otters have superb metabolisms and must eat up to 15 percent of their body weight each day, there's a lot of spraint to go around.

4. OTTER MOMS ARE TOTALLY GAME FOR ADOPTION.

In 2001, a female otter at the Monterey Bay Aquarium gave birth to a stillborn pup on the same day a stranded pup was discovered in the wild nearby. The aquarium staff had previously tried raising pups themselves but found that hand-raised otters became too attached to humans to be released back into the wild. So instead, they dropped the pup in with the female otter, and she immediately went into mom mode. The aquarium has since devised a system of hand-rearing pups for the first 6-8 weeks—mostly for bottle feeding purposes—before handing the pups off to female otters for raising. At six months, the pups are released back into the wild with generally strong results.

5. THEY HAVE THE THICKEST FUR OF ANY MAMMAL IN THE ANIMAL KINGDOM.

Otters can have up to one million hairs per square inch. There are two layers of fur—an undercoat and then longer hairs that we can see. The layers manage to trap air next to the otter's skin, which keeps the otters dry and warm and also helps with buoyancy. Otter pups have so much air trapped in there, they actually can’t dive under water, even if they want to.

6. AN OTTER IS SOMETIMES ONLY AS GOOD AS HIS TOOLS.

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Otters love to eat shelled animals, like clams, but they aren't equipped with the strength to open their food without some help. Therefore, they are big on tools and will often use rocks to help crack into dinner. While they hunt for food underwater, they’ll often store a rock in the skin under their arms for later use.

7. OTTERS ARE POPULAR IN NATIVE AMERICAN CULTURE, BUT FOR VARYING REASONS.

Some tribes consider the otter to be a lucky animal and a symbol of "loyalty and honesty." But some, particularly in present-day Canada and Alaska, viewed the river otter "with awe and dread" and associated the creatures with the undead and drowning. They forbid eating the creatures and were offended when colonial Europeans began hunting the river otters and selling their furs.

8. GIANT OTTERS ARE SUPER CHATTY.

In 2014, a study of giant otters found that the river-dwellers have 22 distinct noises they make for different situations. On top of that, pups have 11 of their own calls that they intersperse with "infant babbling." Among the most notable calls: a "hum graduation" used to tell otters to change directions and a "Hah!" shout when a threat is nearby.

9. OTTERS AND HUMANS CAN COLLABORATE.

In Bangladesh, otters help fisherman maximize their haul. For centuries, fisherman have been training otters to act as herders and chase large schools of fish into the nets.

10. DRONES MAY HELP SCIENTISTS BETTER STUDY OTTERS IN THE WILD.

Keeping an eye on otters in the wild is a tricky task. In the past, observers have usually set up telescopes on shore to try and monitor otters at sea while on land. Otters won't act naturally with humans nearby, and using a telescope on a boat can get tricky in the rollicking ocean. But now, scientists are using unmanned drones with cameras to get an aerial look at otters in their element, making it easier to monitor the creatures as they dive for food and go about their day.

11. SEE A GROUP OF OTTERS? THAT'S A ROMP. OR A BEVY.

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Or a family or a raft. Otter groups go by a few different monikers, all of which are fairly unique to that crew. Generally, a group of otters on land will go by a romp, while a group hanging in the water is called a raft.

12. OTTERS ARE BIG ON PLAY TIME, AND MAKING SLIDES IS AMONG THEIR FAVORITE GAMES.

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Otter families are usually limited to pups and their mothers, and that duo will spend most of their time either feeding or sleeping. In the downtime, though, otters love to play and will often build themselves slides along the banks of rivers.

13. CALIFORNIA SEA OTTERS DIVIDE THEMSELVES IN DIET GUILDS.

Once thought to be gone from the area completely, southern sea otters—known as California sea otters—have been making a comeback in recent years. But with their numbers hovering around just a few thousand, researchers have kept a close eye on the population and their studies have revealed an interesting social structure. The otters, which need to consume 25 percent to 35 percent of their body weight every day in order to maintain their blubber stores and keep themselves warm in the cool waters, are divided into three "dietary guilds": Deep-diving otters that dine on abalone, urchins, and Dungeness crab; medium divers who subsist on clams, worms, and smaller shellfish; and those that stay in shallower waters, feeding on black snails.

14. THE FIRST EUROPEAN TO SET FOOT IN ALASKA WAS ALSO THE FIRST TO DESCRIBE SEA OTTERS.

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Georg Wilhelm Steller was the first to scientifically describe numerous new animals on the 1741 explorative voyage from Russia. Aboard the St. Peter, Steller and other 18th-century explorers crash-landed on mainland Alaska after getting separated from its sister ship. Steller was the first European to set foot on the icy land. Over the course of a rough Alaskan winter, he meticulously documented many species, and while some have since gone extinct (like a sea-cow he described that was hunted into extinction), the adorable otter was among his initial discoveries.

15. BABY OTTERS ARE BUOYANT, BUT THEY CAN'T SWIM ON THEIR OWN.

A mother will often wrap the babies in kelp to keep them in one place while she hunts. Or, she might rely on human resources and otter ingenuity to find a makeshift “playpen” for her pup.

16. THEIR BEHAVIOR ISN'T ALWAYS ADORABLE.

Like many animals, otters sometimes behave in ways that aren't exactly within the bounds of what humans would consider morally acceptable. Even if you find them otherwise adorable, otters' mating habits will no doubt make your stomach turn.

Male otters' mating techniques are violent. They bite their female partner's face during copulation to keep her from slipping away, leaving her with substantial facial wounds. It's not uncommon for female otters to die as a result of these aggressive encounters, either through drowning or from their wounds becoming infected. Male otters have also been known to violently copulate with other species—most notably, baby seals [PDF]. The behavior doesn't stop when the seals die from the trauma. Otters have been known to guard and have sex with the bodies of their victims for up to seven days after they've died.

Scientists hypothesize that these seemingly counterproductive mating habits might be the result of a population imbalance. In California's Monterey Bay, where scientists observed otters trying to copulate with the week-old bodies of dead baby seals, there are far more male otters than females. Facing a lack of female partners, male otters may be engaging in what researchers call "misdirected sexual activity." The area in the bay where the scientists observed the most otter-on-seal mating sessions was also where there was a high population of transient male otters, ones that, unlike more dominant males, don't have an established territory filled with potential mates. In the absence of females of their own kind, then, they turned their typical sexual responses toward the seals. Nature, unfortunately, isn't always pretty.

A version of this story originally ran in 2015.

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