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Sharks flee in terror when killer whales show up
Sharks fear killer whales. How does this impact the ecosystems they share?
- A new study finds that sharks will flee areas they met orcas in for up to a year.
- Killer whales are known to eat sharks, but it is unknown if the sharks are fleeing because they know that too.
- The discovery will change our understanding of how marine ecosystems evolve.
Orcas, also known as "killer whales," are pretty cool. They're usually friendly despite their nickname, and are in an elite club of animals with no natural predators. With a range that spans the world and a coloring reminiscent of an equally popular but much less capable land animal, their image permeates pop culture.
But a new study published in Scientific Reports offers another reason to be impressed by these majestic creatures; they are so intimidating to ocean life that even great white sharks flee in terror before them.
The true apex predator
The study, titled "Killer whales redistribute white shark foraging pressure on seals," results from years of investigations into the movements and behavior of 165 tagged great white sharks, observations and records of killer whale movements, and information on seal populations off the coast of California. They also looked to previous descriptions of shark and whale interactions to give context to their findings.
The sharks immediately turned tail and fled in every time they crossed paths with orcas. They'd also stay away from that place long afterward. Only one observed shark dared venture back to where it had just encountered the whales, and it didn't stick around. Most of the sharks merely fled a bit further up the coastline, while others went much further out to sea to avoid the whales.
Why are they doing this?
Orcas have been known to eat great whites. The remains of the sharks are a grotesque sight to behold and are always missing their livers, no matter how much else remains or is missing. If the orcas have discovered a source of Chianti to pair with them or not remains unknown at this time.
However, we don't currently know if the sharks are fleeing because they understand that risk, because they knew the orcas would fight them for the same food supply, because whales look big and scary to them, or some combination of the three.
Before this gets too frightening, there are no known cases of wild orcas killing humans, and only a few examples of injuries being caused by these interactions. Orcas kept in tiny boxes for long periods can be a bit more violent, but that's another story.
Anything that makes sharks flee in terror will have an impact on the ecosystem. In this case, elephant seals benefit.
Observations of seal populations show a decline in predation events after orcas that can last for an entire year. While orcas occasionally snack on elephant seals, they stick to fish most of the time. It's a boon for the seals in areas the sharks leave, though the seals in the places they flee to might not see it that way. The findings of this study will inform our understanding of seal population fluctuations.
As lead author Salvador Jorgensen explains, the study also demonstrates that "food chains are not always linear. So-called lateral interactions between top predators are fairly well known on land but are much harder to document in the ocean. And because this one happens so infrequently, it may take us a while longer to fully understand the dynamics."
For those wondering how much longer it may take to reach that understanding, this study relied on decades of data on shark, whale, and seal populations in addition to the recently collected information. While demonstrating the value of long-term datasets and the long-term importance of minor interactions is great for science, the impatient may be disappointed at the slow pace of progress.
But the most important take away of this study might be the obvious one:
Never made an orca angry, unless you're tougher than a great white shark.
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A Harvard professor's study discovers the worst year to be alive.
- Harvard professor Michael McCormick argues the worst year to be alive was 536 AD.
- The year was terrible due to cataclysmic eruptions that blocked out the sun and the spread of the plague.
- 536 ushered in the coldest decade in thousands of years and started a century of economic devastation.
The past year has been nothing but the worst in the lives of many people around the globe. A rampaging pandemic, dangerous political instability, weather catastrophes, and a profound change in lifestyle that most have never experienced or imagined.
But was it the worst year ever?
Nope. Not even close. In the eyes of the historian and archaeologist Michael McCormick, the absolute "worst year to be alive" was 536.
Why was 536 so bad? You could certainly argue that 1918, the last year of World War I when the Spanish Flu killed up to 100 million people around the world, was a terrible year by all accounts. 1349 could also be considered on this morbid list as the year when the Black Death wiped out half of Europe, with up to 20 million dead from the plague. Most of the years of World War II could probably lay claim to the "worst year" title as well. But 536 was in a category of its own, argues the historian.
It all began with an eruption...
According to McCormick, Professor of Medieval History at Harvard University, 536 was the precursor year to one of the worst periods of human history. It featured a volcanic eruption early in the year that took place in Iceland, as established by a study of a Swiss glacier carried out by McCormick and the glaciologist Paul Mayewski from the Climate Change Institute of The University of Maine (UM) in Orono.
The ash spewed out by the volcano likely led to a fog that brought an 18-month-long stretch of daytime darkness across Europe, the Middle East, and portions of Asia. As wrote the Byzantine historian Procopius, "For the sun gave forth its light without brightness, like the moon, during the whole year." He also recounted that it looked like the sun was always in eclipse.
Cassiodorus, a Roman politician of that time, wrote that the sun had a "bluish" color, the moon had no luster, and "seasons seem to be all jumbled up together." What's even creepier, he described, "We marvel to see no shadows of our bodies at noon."
...that led to famine...
The dark days also brought a period of coldness, with summer temperatures falling by 1.5° C. to 2.5° C. This started the coldest decade in the past 2300 years, reports Science, leading to the devastation of crops and worldwide hunger.
...and the fall of an empire
In 541, the bubonic plague added considerably to the world's misery. Spreading from the Roman port of Pelusium in Egypt, the so-called Plague of Justinian caused the deaths of up to one half of the population of the eastern Roman Empire. This, in turn, sped up its eventual collapse, writes McCormick.
Between the environmental cataclysms, with massive volcanic eruptions also in 540 and 547, and the devastation brought on by the plague, Europe was in for an economic downturn for nearly all of the next century, until 640 when silver mining gave it a boost.
Was that the worst time in history?
Of course, the absolute worst time in history depends on who you were and where you lived.
Native Americans can easily point to 1520, when smallpox, brought over by the Spanish, killed millions of indigenous people. By 1600, up to 90 percent of the population of the Americas (about 55 million people) was wiped out by various European pathogens.
Like all things, the grisly title of "worst year ever" comes down to historical perspective.
A simple trick allowed marine biologists to prove a long-held suspicion.
- It's long been suspected that sharks navigate the oceans using Earth's magnetic field.
- Sharks are, however, difficult to experiment with.
- Using magnetism, marine biologists figured out a clever way to fool sharks into thinking they're somewhere that they're not.
For some time, scientists have suspected that sharks belong among the growing number of animals known to navigate using Earth's magnetic field. Testing anything with a shark, though, requires some care.
The key was selecting the right candidate. Keller and his colleagues chose the bonnethead shark, Sphyrna tiburo, a small critter that summers at Turkey Point Shoal off the coast of the Florida State University Coastal and Marine Laboratory with which Keller is affiliated.
Bonnetheads elsewhere have been known to complete 620-mile roundtrip migrations. As the lab's Dean Grubbs puts it, "That's not bad for a shark that is only two to three feet long. The question is how do they find their way back to that same estuary year after year." There's a report of a great white shark migrating between two locations, one in South Africa and another in Australia, year after year.
The research is published in Current Biology.
Keller and his team rounded up 20 local juvenile bonnetheads and transported them into a holding tank at the marine lab. For the tests, the researchers simulated three real-world magnetic fields. As the various magnetic fields were activated, the sharks' movements were captured by GoPro cameras and their average swimming orientations calculated by software.
The first simulation, serving as a control, mimicked the magnetic field of the nearby shoal from which the sharks had been captured. When this field was activated, the sharks essentially acted like they were "home," just swimming around as they do.
A second field was the magnetic equivalent of a location 600 kilometers south of the lab within the Gulf of Mexico. When this field was activated, the sharks, apparently mistaking themselves for being far south in the Gulf, began swimming northward toward the shoal.
The opposite occurred with a field standing in for a location in continental North America 600 km north of their home shoal — the sharks began swimming southward.
"For 50 years," says Keller, "scientists have hypothesized that sharks use the magnetic field as a navigational aid. This theory has been so popular because sharks, skates, and rays have been shown to be very sensitive to magnetic fields. They have also been trained to react to unique geomagnetic signatures, so we know they are capable of detecting and reacting to variation in the magnetic field."
His team's experiments confirm what's long been suspected, Keller says: "Sharks use map-like information from the geomagnetic field as a navigational aid. This ability is useful for navigation and possibly maintaining population structure."
A machine learning system lets visitors at a Kandinsky exhibition hear the artwork.
Have you ever heard colors?
As part of a new exhibition, the worlds of culture and technology collide, bringing sound to the colors of abstract art pioneer Wassily Kandinsky.
Kandinsky had synesthesia, where looking at colors and shapes causes some with the condition to hear associated sounds. With the help of machine learning, virtual visitors to the Sounds Like Kandinsky exhibition, a partnership project by Centre Pompidou in Paris and Google Arts & Culture, can have an aural experience of his art.
An eye for music
Kandinsky's synesthesia is thought to have heavily influenced his painting. Seeing yellow summoned up trumpets, evoking emotions like cheekiness; reds produced violins portraying restlessness; while organs representing heavenliness he associated with blues, according to the exhibition notes.
Virtual visitors are invited to take part in an experiment called Play a Kandinsky, which allows them to see and hear the world through the artist's eyes.
Kandinsky's synesthesia is thought to have heavily influenced his 1925 painting Yellow, Red, Blue.Image: Guillaume Piolle/Wikimedia Commons
In 1925, the artist's masterpiece, "Yellow, Red, Blue", broke new ground in the world of abstract art, guiding the viewer from left to right with shifting shapes and shades. Almost a century after it was painted, Google's interactive tool lets visitors click different parts of the artwork to journey through the artist's description of the colors, associated sounds and moods that inspired the work.
But Google's new toy is not the only tool developed to enhance the artistic experience.
Artist Neil Harbisson has developed an artificial way to emulate Kandinsky by turning colors into sounds. He has a rare form of color blindness and sees the world in greyscale. But a smart antenna attached to his head translates dominant colors into musical notes, creating a real-world soundtrack of what's in front of him. The invention could open up a new world for people who are color blind.
A new study suggests that private prisons hold prisoners for a longer period of time, wasting the cost savings that private prisons are supposed to provide over public ones.