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Spiders hunt in PACKS of hundreds, using web vibrations to coordinate attacks – Daily Mail

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The stuff of nightmares! Spiders hunt in PACKS of hundreds, using web vibrations to coordinate attacks on prey up to several hundreds times their size, study reveals

  • Scientists studied Anelosimus eximius, a South American ‘social’ spider species
  • It lives in large, curved non-stick webs and swarm over insects that fall into them
  • The spiders collectively do this using a cunning two-pronged attack, they found 
  • Anelosimus eximius is one of only about 25 species of ‘social’ spiders worldwide


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It’s usually the lion that’s known for hunting in packs, using coordinated movements to ambush its unfortunate prey. 

But a new study shows how a species of spider, called Anelosimus eximius, similarly takes down its prey in packs using specialised web vibrations.

The spider species, which is native to South America, lives in large towering non-stick webs and can suddenly swarm over insects that fall into them.  

They collectively do this using a cunning two-pronged attack, involving moving as one and then staying still to perceive vibrations coming through their web. 

Researchers used a dead fly connected to a vibration generator, brought into contact with a web, to trigger the collective spider hunting behaviour

A. EXIMIUS: SOCIAL SPIDER HUNTS IN PACKS

Anelosimus eximius is a colonial social spider native to South America. Colonies consist of thousands of spiders. 

The species performs tasks that are shared through the colony, including web maintenance and construction, brood care, defenses and attacking prey for when insects hit their trap.

What’s more, the spiders cooperate when capturing the trapped insects, using coordinated movements. 

The spiders appear to adjust their behavior to match the situation or the prey. 

Source: Animal Diversity Web 

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The study was led by Raphaël Jeanson, a researcher at the French National Centre for Scientific Research, Paris (CNRS), and published in Proceedings of the National Academy of Sciences

The researchers used a dead fly connected to a vibration generator, brought into contact with a web, to trigger the collective spider hunting behaviour in French Guiana. 

‘When the prey falls in the web, this triggers the movement of the spiders,’ Jeanson told Live Science

‘But after a while, they all stop for a few milliseconds before they start moving again.’

Social spiders are notable for living together in large colonies, cooperating on prey capture, sharing parental duties and rarely straying from their basket-shaped nests.

Within the 50,000 known species of spider, about 20 have developed a permanent social life characterised by such cooperation. 

Among these cooperative spiders, A. eximius may be one of only two species that hunt ‘in packs’, helping them catch insects including moths and grasshoppers. 

A. eximius colonies can house several thousand individuals of all ages, co-existing peacefully in gigantic webs that often reach several cubic metres. 

Anelosimus eximius (pictured here in French Guyana) is a species of social spider. Colonies consist of thousands of spiders

Anelosimus eximius (pictured here in French Guyana) is a species of social spider. Colonies consist of thousands of spiders

BENEFITS OF BEING SOCIAL 

For spiders, it’s thought there are many associated benefits to becoming smaller in size. 

Smaller body sizes means that fewer resources are needed for each spider to mature, which leads to less competition for limited resources within a colony. So a single large insect can go a long way, feeding many of the group’s inhabitants. 

Second, although smaller body sizes are accompanied with the production of fewer eggs per female, social spiders invest in quality over quantity of offspring, producing much fewer but significantly larger eggs than their non-social contemporaries. 

Also, the ability to mature at a smaller size allows for some level of flexibility as a response to unpredictable environmental conditions. 

Source: University of Portsmouth   

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‘Nests are typically composed of a horizontal basket-shaped silken sheet and a network of vertical threads, connected to the vegetation, used to intercept flying prey,’ the authors say.

‘A massive and rapid accumulation of spiders on the prey is all the more important as the webs of A. eximius are not sticky and the risk is high of the prey escaping before being seized by spiders.’ 

It’s already know that the spiders of this species cooperate when capturing insects trapped on the web using coordinated movements.  

By combining fieldwork and modelling, the research team identified the actions involved in the synchronisation of these movements.  

A. eximius spiders close in on prey in two stages depending on web vibrations – they close in on their struggling victim in unison, or, alternatively stand still as one, the team found. 

‘An individual’s decision to move depends on the relative intensity of vibrations emitted by the prey and the moving spiders,’ the team say in their paper.

‘This rule allows the group to adapt quickly to any change in prey size or the number of spiders involved in the hunt.’ 

Synchronisation involves a modulation of each spider’s behaviour, according to the relative intensity of the prey’s signals compared to those of the other spiders. 

In other words, the spiders remain motionless on the web when vibrations emitted by fellow spiders are masking vibrations coming from prey. 

Social spider colony (Anelosimus eximius) in French Guyana. Social spiders are notable for living together in large colonies, cooperating on prey capture, sharing parental duties and rarely straying from their basket-shaped nests

Social spider colony (Anelosimus eximius) in French Guyana. Social spiders are notable for living together in large colonies, cooperating on prey capture, sharing parental duties and rarely straying from their basket-shaped nests

‘It’s a bit like when you are in a room with people chatting,’ said Jeanson. 

This coordination increases the spiders’ ability to detect prey and optimises their hunting performance.  

In this way, they are able to capture prey up to several hundred times their size.  

Interestingly, the more social spiders are, the smaller they tend to be, meaning that spiders you’re unlikely to find gigantic spiders hunting in packs. 

Female A. eximius spiders range in size from 0.17-inch to 0.23-inch (4.4 to 6mm), while males are likely even smaller, according to Animal Diversity Web. 

Although smaller body sizes are accompanied with the production of fewer eggs per female, social spiders invest in quality over quantity of offspring.

In other words, they produce much fewer but significantly larger eggs than their non-social contemporaries, according to researchers at the University of Portsmouth.  

SPIDERS THAT HUNT IN PACKS CAN BRING DOWN PREY MORE THAN 22 TIMES THEIR SIZE BUT ARE MORE LIKELY TO REMAIN SMALL, STUDY SHOWS 

Spiders that hunt in packs can bring down prey more than 22 times their size, while solitary arachnids only tend to target insects half as big as themselves, 2020 research revealed.

Tiny tangle-web social spiders known as Anelosimus eximius live in their thousands in webs up to 25-foot long, suspended in the trees of the South American rainforest.

Known for eating larger prey, they can take on insects as large as the four-and-a-half-inch giant grasshopper, swarming over it before it can escape.

A. eximius is one of 33 species studied by researchers at the University of Portsmouth that convinced them ‘social’ spiders are more likely to stay small.

Social spiders tend to live in large towering webs and swarm over insects that fall into them (pictured)

Social spiders tend to live in large towering webs and swarm over insects that fall into them (pictured)

They found that while the group-living arachnids targeted prey two-and-a-half times their size on average, solitary spiders preferred to eat creatures around half their size. 

The researchers made the discovery by comparing the ratio of each species body size by the average size of their prey. 

Eight species of velvet spiders, genus Stegodyphus, found in Africa, Israel and India were examined alongside 25 species, genus Anelosimus, from the Americas.

Spiders in the Anelosimus group varied from 0.07 to 0.2 inches, while those in Stegodyphus varied from 0.3 to 0.9 inches, with the social spiders tending to be much smaller.

Senior lecturer in Zoology, Lena Grinsted, said her findings suggest that working together lessens the need for spiders to grow big.

‘Our argument is that when these spiders start co-operating in catching prey, they can still catch the same really large prey, even if they start to mature at a smaller body size,’ she said.

‘And a smaller body size carries with it multiple overall fitness benefits when you live in a crowded group.’ 

Dr Grinsted said being smaller would mean a larger insect could feed more group members and fewer eggs would be produced, ensuring higher quality offspring.

She added that death rates are reduced in social species as they build large, more-protective, nest structures and do not need to risk travelling to find a mate.

She dubbed her theory the ‘prey to predator size ratio hypothesis’.

‘When spiders evolve the ability to catch prey co-operatively, we see a beneficial increase in the prey:predator body-size ratio,’ she said.

‘This increase can be achieved either by catching larger prey, as the classic theory suggests, or by evolving a smaller predator body size, as we see has happened in some social spiders.’    

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Here’s how Helene and other storms dumped a whopping 40 trillion gallons of rain on the South

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More than 40 trillion gallons of rain drenched the Southeast United States in the last week from Hurricane Helene and a run-of-the-mill rainstorm that sloshed in ahead of it — an unheard of amount of water that has stunned experts.

That’s enough to fill the Dallas Cowboys’ stadium 51,000 times, or Lake Tahoe just once. If it was concentrated just on the state of North Carolina that much water would be 3.5 feet deep (more than 1 meter). It’s enough to fill more than 60 million Olympic-size swimming pools.

“That’s an astronomical amount of precipitation,” said Ed Clark, head of the National Oceanic and Atmospheric Administration’s National Water Center in Tuscaloosa, Alabama. “I have not seen something in my 25 years of working at the weather service that is this geographically large of an extent and the sheer volume of water that fell from the sky.”

The flood damage from the rain is apocalyptic, meteorologists said. More than 100 people are dead, according to officials.

Private meteorologist Ryan Maue, a former NOAA chief scientist, calculated the amount of rain, using precipitation measurements made in 2.5-mile-by-2.5 mile grids as measured by satellites and ground observations. He came up with 40 trillion gallons through Sunday for the eastern United States, with 20 trillion gallons of that hitting just Georgia, Tennessee, the Carolinas and Florida from Hurricane Helene.

Clark did the calculations independently and said the 40 trillion gallon figure (151 trillion liters) is about right and, if anything, conservative. Maue said maybe 1 to 2 trillion more gallons of rain had fallen, much if it in Virginia, since his calculations.

Clark, who spends much of his work on issues of shrinking western water supplies, said to put the amount of rain in perspective, it’s more than twice the combined amount of water stored by two key Colorado River basin reservoirs: Lake Powell and Lake Mead.

Several meteorologists said this was a combination of two, maybe three storm systems. Before Helene struck, rain had fallen heavily for days because a low pressure system had “cut off” from the jet stream — which moves weather systems along west to east — and stalled over the Southeast. That funneled plenty of warm water from the Gulf of Mexico. And a storm that fell just short of named status parked along North Carolina’s Atlantic coast, dumping as much as 20 inches of rain, said North Carolina state climatologist Kathie Dello.

Then add Helene, one of the largest storms in the last couple decades and one that held plenty of rain because it was young and moved fast before it hit the Appalachians, said University of Albany hurricane expert Kristen Corbosiero.

“It was not just a perfect storm, but it was a combination of multiple storms that that led to the enormous amount of rain,” Maue said. “That collected at high elevation, we’re talking 3,000 to 6000 feet. And when you drop trillions of gallons on a mountain, that has to go down.”

The fact that these storms hit the mountains made everything worse, and not just because of runoff. The interaction between the mountains and the storm systems wrings more moisture out of the air, Clark, Maue and Corbosiero said.

North Carolina weather officials said their top measurement total was 31.33 inches in the tiny town of Busick. Mount Mitchell also got more than 2 feet of rainfall.

Before 2017’s Hurricane Harvey, “I said to our colleagues, you know, I never thought in my career that we would measure rainfall in feet,” Clark said. “And after Harvey, Florence, the more isolated events in eastern Kentucky, portions of South Dakota. We’re seeing events year in and year out where we are measuring rainfall in feet.”

Storms are getting wetter as the climate change s, said Corbosiero and Dello. A basic law of physics says the air holds nearly 4% more moisture for every degree Fahrenheit warmer (7% for every degree Celsius) and the world has warmed more than 2 degrees (1.2 degrees Celsius) since pre-industrial times.

Corbosiero said meteorologists are vigorously debating how much of Helene is due to worsening climate change and how much is random.

For Dello, the “fingerprints of climate change” were clear.

“We’ve seen tropical storm impacts in western North Carolina. But these storms are wetter and these storms are warmer. And there would have been a time when a tropical storm would have been heading toward North Carolina and would have caused some rain and some damage, but not apocalyptic destruction. ”

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Follow AP’s climate coverage at https://apnews.com/hub/climate

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Follow Seth Borenstein on Twitter at @borenbears

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Associated Press climate and environmental coverage receives support from several private foundations. See more about AP’s climate initiative here. The AP is solely responsible for all content.

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‘Big Sam’: Paleontologists unearth giant skull of Pachyrhinosaurus in Alberta

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It’s a dinosaur that roamed Alberta’s badlands more than 70 million years ago, sporting a big, bumpy, bony head the size of a baby elephant.

On Wednesday, paleontologists near Grande Prairie pulled its 272-kilogram skull from the ground.

They call it “Big Sam.”

The adult Pachyrhinosaurus is the second plant-eating dinosaur to be unearthed from a dense bonebed belonging to a herd that died together on the edge of a valley that now sits 450 kilometres northwest of Edmonton.

It didn’t die alone.

“We have hundreds of juvenile bones in the bonebed, so we know that there are many babies and some adults among all of the big adults,” Emily Bamforth, a paleontologist with the nearby Philip J. Currie Dinosaur Museum, said in an interview on the way to the dig site.

She described the horned Pachyrhinosaurus as “the smaller, older cousin of the triceratops.”

“This species of dinosaur is endemic to the Grand Prairie area, so it’s found here and nowhere else in the world. They are … kind of about the size of an Indian elephant and a rhino,” she added.

The head alone, she said, is about the size of a baby elephant.

The discovery was a long time coming.

The bonebed was first discovered by a high school teacher out for a walk about 50 years ago. It took the teacher a decade to get anyone from southern Alberta to come to take a look.

“At the time, sort of in the ’70s and ’80s, paleontology in northern Alberta was virtually unknown,” said Bamforth.

When paleontogists eventually got to the site, Bamforth said, they learned “it’s actually one of the densest dinosaur bonebeds in North America.”

“It contains about 100 to 300 bones per square metre,” she said.

Paleontologists have been at the site sporadically ever since, combing through bones belonging to turtles, dinosaurs and lizards. Sixteen years ago, they discovered a large skull of an approximately 30-year-old Pachyrhinosaurus, which is now at the museum.

About a year ago, they found the second adult: Big Sam.

Bamforth said both dinosaurs are believed to have been the elders in the herd.

“Their distinguishing feature is that, instead of having a horn on their nose like a triceratops, they had this big, bony bump called a boss. And they have big, bony bumps over their eyes as well,” she said.

“It makes them look a little strange. It’s the one dinosaur that if you find it, it’s the only possible thing it can be.”

The genders of the two adults are unknown.

Bamforth said the extraction was difficult because Big Sam was intertwined in a cluster of about 300 other bones.

The skull was found upside down, “as if the animal was lying on its back,” but was well preserved, she said.

She said the excavation process involved putting plaster on the skull and wooden planks around if for stability. From there, it was lifted out — very carefully — with a crane, and was to be shipped on a trolley to the museum for study.

“I have extracted skulls in the past. This is probably the biggest one I’ve ever done though,” said Bamforth.

“It’s pretty exciting.”

This report by The Canadian Press was first published Sept. 25, 2024.

The Canadian Press. All rights reserved.

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The ancient jar smashed by a 4-year-old is back on display at an Israeli museum after repair

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TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.

Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.

Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.

The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.

The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.

It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.

Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.

Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.

Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.

Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.

Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.

The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”

The Canadian Press. All rights reserved.

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