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Elephant seals drift off to sleep while diving far below the ocean surface

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Cetaceans (whales and dolphins) and otariids (fur seals and sea lions) keep one side of their brains awake while the other is asleep (unihemispheric sleep). In most other mammals, including phocids (true seals) and humans, both hemispheres of the brain are asleep at the same time. Credit: Graphic by Jessica Kendall-Bar

For the first time, scientists have recorded brain activity in a free-ranging, wild marine mammal, revealing the sleep habits of elephant seals during the months they spend at sea.

The new findings, published April 20 in Science, show that while elephant seals may spend 10 hours a day sleeping on the beach during the breeding season, they average just 2 per day when they are at sea on months-long foraging trips. They sleep for about 10 minutes at a time during deep, 30-minute dives, often spiraling downward while fast asleep, and sometimes lying motionless on the seafloor.

First author Jessica Kendall-Bar led the study as a UC Santa Cruz graduate student working with Daniel Costa and Terrie Williams, both professors of ecology and evolutionary biology at UCSC.

“For years, one of the central questions about elephant seals has been when do they sleep,” said Costa, who directs UCSC’s Institute of Marine Sciences. Costa’s lab has led the UCSC elephant seal research program at Año Nuevo Reserve for over 25 years, using increasingly sophisticated tags to track the movements and diving behavior of the seals during their foraging migrations, when they head out into the North Pacific Ocean for as long as eight months.

“The dive records show that they are constantly diving, so we thought they must be sleeping during what we call drift dives, when they stop swimming and slowly sink, but we really didn’t know,” Costa said. “Now we’re finally able to say they’re definitely sleeping during those dives, and we also found that they’re not sleeping very much overall compared to other mammals.”

In fact, during their months at sea, elephant seals rival the record for the least sleep among all mammals, currently held by African elephants, which appear to sleep just two hours per day based on their movement patterns.

“Elephant seals are unusual in that they switch between getting a lot of sleep when they’re on land, over 10 hours a day, and two hours or less when they’re at sea,” said Kendall-Bar, who is currently a postdoctoral fellow at UC San Diego’s Scripps Institution of Oceanography.

Elephant seals are most vulnerable to predators such as sharks and killer whales when they are at the surface in the open ocean, so they only spend a minute or two breathing at the surface in between dives.

[embedded content]
Data-driven animation showing the phases of a sleeping dive to 263 meters. Credit: Animation by Jessica Kendall-Bar.

“They’re able to hold their breath for a long time, so they can go into a deep slumber on these dives deep below the surface where it’s safe,” Kendall-Bar said.

Kendall-Bar developed a system that can reliably record (as an electroencephalogram or EEG) in wild elephant seals during their normal diving behavior at sea. With a neoprene headcap to secure the EEG sensors and a small data logger to record the signals, the system can be recovered when the animals return to the beach at Año Nuevo.

“We used the same sensors you’d use for a human sleep study at a sleep clinic and a removable, flexible adhesive to attach the headcap so that water couldn’t get in and disrupt the signals,” Kendall-Bar said.

In addition to the EEG system, the seals carried time-depth recorders, accelerometers, and other instruments that allowed the researchers to track the seals’ movements along with the corresponding brain activity. The recordings show diving seals going into the deep sleep stage known as while maintaining a controlled glide downward, then transitioning into rapid-eye-movement (REM) sleep, when causes them to turn upside down and drift downwards in a “sleep spiral.”

“They go into slow-wave sleep and maintain their body posture for several minutes before they transition into REM sleep, when they lose postural control and turn upside down,” Kendall-Bar said.

At the depths at which this happens, the seals are usually negatively buoyant and continue to fall passively in a corkscrew spiral “like a falling leaf,” Williams said. In shallower waters over the continental shelf, elephant seals sometimes sleep while resting on the seafloor.

“It doesn’t seem possible that they would truly go into paralytic REM sleep during a dive, but it tells us something about the decision-making processes of these seals to see where in the water column they feel safe enough to go to sleep,” said Williams, who directs the Comparative Neurophysiology Lab at UCSC.

In developing the new EEG instrument, Kendall-Bar first deployed it on elephant seals housed temporarily in the marine mammal facilities at UCSC’s Long Marine Laboratory. The next step was to deploy it on animals in the elephant seal colony at Año Nuevo Reserve north of Santa Cruz, where researchers could observe the animals on the beach.

When elephant seals go into rapid-eye-movement (REM) sleep during deep dives, sleep paralysis causes them to turn upside down and drift downwards in a “sleep spiral.” This data-driven graphic shows sleeping postures every 20 seconds, with accompanying 30-second segments of EEG traces in the background. Credit: Jessica Kendall-Bar

“I spent a lot of time watching sleeping seals,” Kendall-Bar said. “Our team monitored instrumented seals to make sure they were able to reintegrate with the colony and were behaving naturally.”

Some of those seals took short excursions into the water, but to observe diving behavior the researchers used a translocation procedure developed by Costa’s lab. Juvenile female elephant seals outfitted with the EEG sensors and trackers were transported from Año Nuevo to Monterey and released on a beach at the southern end of Monterey Bay. Over the next few days, the animals would swim back to Año Nuevo across the deep Monterey Canyon, where their dive behavior is very similar to that seen during much longer foraging trips in the open ocean.

With data on brain activity and dive behavior from 13 juvenile female elephant seals, including a total of 104 sleep dives, Kendall-Bar developed a highly accurate algorithm for identifying periods of sleep based on the dive data alone. This enabled her to estimate sleep quotas for 334 adult seals using data recorded over several months during their foraging trips.

“Because of the dataset that Dan Costa has curated over 25 years of working with at Año Nuevo, I was able to extrapolate our results to over 300 animals and get a population-level look at sleep behavior,” said Kendall-Bar, who now plans to use similar methods to study brain activity in other species of seals and sea lions and in human freedivers.

Williams called Kendall-Bar’s work on the project a tour de force. “It’s an amazing feat to pull this off,” she said. “She developed an EEG system to work on an animal that’s diving several hundred meters in the ocean. Then she uses the data to create data-driven animations so we can really visualize what the animal is doing as it dives through the water column.”

The results may be helpful for conservation efforts by revealing a “sleepscape” of preferred resting areas, Williams said. “Normally, we’re concerned about protecting the areas where animals go to feed, but perhaps the places where they sleep are as important as any other critical habitat,” she said.

More information:
Jessica M. Kendall-Bar, Brain activity of diving seals reveals short sleep cycles at depth, Science (2023). DOI: 10.1126/science.adf0566. www.science.org/doi/10.1126/science.adf0566

Citation:
Elephant seals drift off to sleep while diving far below the ocean surface (2023, April 20)
retrieved 21 April 2023
from https://phys.org/news/2023-04-elephant-drift-ocean-surface.html

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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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