Is Your Brain Sleeping While You're Awake?

If you think you can function on minimal sleep, here's a wake-up call: Parts of yourbrainmay doze off even if you're totally awake, according to a new study in rats.

Scientists observed the electrical activity of brains in rats forced to stay up longer than usual. Problem-solving brain regions fell into a kind of"local sleep"—a condition likely in sleep-deprived humans too, the study authors say.

Surprisingly, when sections of the rats' brains entered these sleeplike states,"you couldn't tell that {the rats} are in any way in a different state of wakefulness,"said study co-authorGiulio Tononi, a neuroscientist at the University of Wisconsin, Madison.

Despite these periods of local sleep, overall brain activity—and the rats’ behaviors—suggested the animals were fully awake.

This phenomenon of local sleep is"not just an interesting observation of unknown significance,"Tononi said. It"actually affects behavior—you make a mistake."

For example, when the scientists had the rats perform a challenging task—using their paws to reach sugar pellets—the sleep-deprived animals had trouble completing it.

(See"Secrets of Sleeping Soundly Uncovered.")

Sleep Allows Neurons to Reset?

Tononi and colleagues recorded the electrical activity of lab rats via electroencephalogram (EEG) sensors connected to the rodents' heads.
As predicted, when the rats were awake, their neurons—nerve cells that collect and transmit signals in the brain—fired frequently and irregularly.

When the animals slept, their neurons fired less often, usually in a regular up-and-down pattern that manifests on the EEG as a"slow wave."Called non-rapid eye movement, this sleep stage accounts for about 80 percent of all sleep in both rats and people.

The researchers used toys to distract the rats into staying awake for a few hours—normally"rats take lots of siestas,"Tononi noted.

The team discovered that neurons in two sections of these overtired rats' cerebral cortexes entered a slow-wave stage that is essentially sleep.

Why Do We Sleep?

It's unknown why parts of an awake brain nod off, though it may have something to do with why mammals sleep—still an open question, said Tononi, whose study appears tomorrow in the journalNature.(Read aboutmysteries of why we sleep inNational Geographicmagazine.)

According to one leading theory, since neurons are constantly"recording"new information, at some point the neurons need to"turn off"in order to reset themselves and prepare to learn again.

"If this hypothesis is correct, that means that at some point {if you're putting off sleep} you're beginning to overwhelm your neurons—you are reaching the limit of how much input they can get."

(See"Sleep Cherry-picks Memories, Boosts Cleverness.")

So the neurons"take the rest, even if they shouldn't"—and there's a price to pay in terms of making"stupid"errors, he said.

(Seebrain pictures.)

Even"Alert"People Make Mistakes

Sleep deprivation may have dangerous consequences, Tononi said—and those mistakes may become more common.

For one, many people are getting fewer z's. In 2008 about 29 percent of U.S. adults reported sleeping fewer than seven hours per night, and 50 to 70 million had chronic sleep and wakefulness disorders, according to theU.S. Centers for Disease Control and Prevention. Adults generally need about seven to nine hours of sleep a day,according to the National Sleep Foundation.

(TakeNational Geographicmagazine's sleep quiz.)

What's more, you don't need to feel sleepy to screw up, Tononi emphasized.

"Even if you may feel that you're fit and fine and are holding up well,"he said,"some parts of your brain may not {be} ... and those are the ones that make judgments and decisions."

National Geographic News

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Pictures: Fire Ant Swarms Form Living Life Rafts

When a city floods, humans stack sandbags and raise levees. When a fire ant colony floods, the ants link up to form a literal life raft, such as the one pictured. Now, new research shows exactly how the ants manage this feat.

Engineering professor David Hu and graduate student Nathan J. Mlot atGeorgia Institute of Technologyhad heard reports of ant rafts in the wild that last for weeks. (Watch a fire ant video.)

"They'll gather up all the eggs in the colony and will make their way up through the underground network of tunnels, and when the flood waters rise above the ground, they'll link up together in these massive rafts,"Mlot said. Together with Georgia Tech systems-engineering professor Craig Tovey, the scientists collected fire ants and dunked clumps of them in water to see what would happen.

In less than two minutes the ants had linked"hands"to form a floating structure that kept all the insects safe. Even the ants down below can survive this way, thanks to tiny hairs on the ants' bodies that trap a thin layer of air.

"Even when they're on the bottom of the raft, they never technically become submerged,"Mlot said.

The fire ant life raft research is described in the April 25 issue of the Proceedings of the National Academy of Sciences.

—Rachel Kaufman

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Odd Animal Deaths, Deformities Linked to Gulf Oil Spill?

On the first anniversary of theGulf oil spill, scientists are observing strange deaths and deformities in animals that could be related to the disaster, experts say.

In the past six months, the numbers of dolphin and sea turtle deaths in theGulf of Mexico (map)have risen, and some fish that inhabit the Gulf'scoral reefshave developed abnormalities. (Read more about the Gulf oil spill anniversary.)

Yet projects to document and measure the oil's effects on Gulf marine life are still in the very early stages, scientists caution. Preliminary results may not be available for months, and it may be several years before any kind of scientific consensus is reached.

(See an interactive of the Gulf's layers of life inNational Geographicmagazine.)

Such uncertainty is not unusual for oil-spill studies, notedWilliam Patterson, a marine biologist at the University of West Florida (UWF) in Pensacola.

"If you look at the literature surrounding theExxon Valdezoil spill {in 1989}, there are still some unknowns associated with that,"Patterson said.

"What we know {in the case ofExxon Valdez} is that there was an insult to the system, that there were effects on the food web and ecosystem, and that some species have not recovered to the levels they were at before."(Related:"Exxon ValdezAnniversary: 20 Years Later, Oil Remains.")

Some of theExxon Valdezoil's effects are circumstantial evidence, he added,"but it's pretty compelling evidence."

Mysterious Spike in Dolphin, Turtle Deaths

This winter, an alarmingly high number ofbottlenose dolphins—113 at last count—washed up dead on U.S. shores, according to theNational Oceanic and Atmospheric Administration (NOAA). The agency confirmed in early April that six of the bodies hadDeepwater Horizonoil on them.

(Read more:"Dolphin-Baby Die-Off in Gulf Puzzles Scientists.")

"What's important to note, however, is that even though they have this oil on them, it may not be the cause of death,"Blair Mase, NOAA's marine-mammal investigations coordinator, told reporters at a news briefing April 7.

"That's something the investigative team and our working groups are looking into."

So far this year scientists have also seen a rise in deaths of various species of Gulf sea turtle hatchlings. But NOAA researchers say the culprits may be contact with boats and fishing gear and possibly poisoning by toxins in algal blooms, which naturally appear in the Gulf each spring.

"The carcasses that we have looked at . . . had no visible oil on them,"said Barbara Schroeder, national sea turtle coordinator for NOAA.

(Relatedpictures:"Baby Gulf Turtles Released Into Atlantic.")

Fish Found With Deformed Ovaries, Missing Fins

Meanwhile, other researchers are looking for effects of the oil on other marine species, such asfish, crustaceans, andcorals.

UWF's Patterson has recently observed an increase in physical abnormalities consistent with oil exposure in red snappers that live in Gulf coral reefs.

"There are parasites showing up on the fish. They're always present, but this fall and winter we're seeing them in what appears to be higher abundances,"Patterson said.

Some of the fish are suffering so severely from a disease called fin rot that entire fins are missing—something Patterson said he has never seen before. Some female red snappers also have been discovered with hardened or deformed ovaries.

(Also see"Sex-Changing Chemicals Can Wipe Out Fish, Study Shows.")

Other red snappers have strange pigmentation issues, Patterson said."We have some images of red snappers sent to us by commercial fishermen that have black bands across the sides of the fish that is discolored skin."

These symptoms are not unusual in themselves, Patterson said, but the fact that they're appearing at what looks to be increased rates at the same time concerns him.

"Some of these things that we're seeing are classic symptoms of hydrocarbon exposure that have been documented in lab studies."

For example, the odd pigmentation could be caused by the fish's kidney or bile duct being affected or clogged by oil components.

"So it does seem to be pointing in one direction, but we don't have anything definitive yet to tell the full story."

Chuck Jagoe, an environmental toxicologist at Florida A&M University in Tallahassee, is working with Patterson to test Gulf red snappers for telltale enzymes that are produced when the fish flush toxic oil components from their bodies.

"These enzymes are associated with the detoxification process,"Jagoe said.

"They can give us an indication that the animal has not only been exposed to {oil} compounds, but that the compound is having some kind of biological effect."

Jagoe has just begun testing the fish, and the first results won't be available until at least early summer.

One Species Not Enough Evidence

UWF's Patterson said he also plans to investigate whether other Gulf species are exhibiting symptoms similar to those of the snappers.

Even nearly a year after the disaster, oil could still be lurking in the Gulf's waters, he added.

"Oil is not one thing,"Patterson said."It's thousands of organic compounds. Some of them are fairly {unstable} and microbes break them down very quickly, while others could persist for a long time."

(See"Why the Gulf Oil Spill Isn't Going Away.")

Finding other affected species will be crucial to making a case that the oil spill is having a systemic effect on Gulf fish species, saidProsanta Chakrabarty, a fish biologist at Louisiana State University in Baton Rouge who was not involved in the snapper project.

"With one species, we can't really tell,"Chakrabarty said.

He also noted that red snappers are already a vulnerable species due tooverfishing, and that it's possible the symptoms that Patterson is seeing are due to inbreeding caused by a decreased population.

Whatever the cause of the deformities, though,"the oil spill didn't help any,"he said.

Fish Populations Measured via GPS

Chakrabarty is involved in another project calledDepthmap, which aims to use fish-population data collected using GPS technology before and after the spill to investigate the Gulf oil spill's impact on marine life. Museum records are also used to fill out pre-spill data.

"If, for example, 80 percent of Gulf pancake batfishes were found off the coast of Louisiana and they're not there anymore,"then that could be an indication the spill negatively affected the species, he said.

(See"Two New 'Walking' Batfish Species Found.")

And if this pattern is repeated for many fish species, it would indicate the spill has had a pervasive impact on Gulf marine life.

Chakrabarty's team hopes to gather pre- and post-spill population data for 600 fish species in the northern Gulf, but has only begun analysis for a fraction of that number due to limited funding.

His early results suggest that of the 53 species examined so far, 43 had major populations that lived in regions that were in the path of the spill.

Deep-Sea Effects Leave Scientists in the Dark

Even if Depthmap's goals were met, however, scientists would still know only about the impact the spill had on fish that live in relatively shallow water. But the spill's largest potential damage is to deep-sea creatures, Chakrabarty said. (See pictures of deep-sea animals.)

The broken wellhead blew at 5,000 feet (1,500 meters) underwater, and plumes of gushing oil floated nearly 1 mile (1.6 kilometers) up from the seafloor, polluting different layers of water as they rose.

"We knew that the oil wouldn't last at the surface for very long, but what happened at the deep sea?"Chakrabarty said.

Of particular concern, he added, are the effects of the oil dispersants piped into the waters near the wellhead in a desperate bid to break apart the oil before it reached the surface.

"The deep sea is such a stable environment. . . . It isn't used to perturbations like this influx of {dispersants},"Chakrabarty said.

"So what the impact {is} of having {dispersants} enter that area, even momentarily, is difficult to understand."

(See"Gulf Spill Dispersants Surprisingly Long-lasting.")

Despite his concerns about the deformed fish, UWF's Patterson added that it's important for scientists not to jump to conclusions.

"As scientists, we shouldn't be unwilling to say we're not quite sure,"he said.

"Instead of going out on a limb and making grand announcements, I think it's a safer approach to say, Well, these are issues that we're seeing that we're not able to attribute to any one thing, but we're concerned about them.

"And that's where we are."

*The photographer, a commercial fisher in the Gulf, requested to remain anonymous.

forNational Geographic News

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Gulf Spill Photos: 9 Animal Victims—Plus 2 Survivors

Abottlenose dolphinbreaks the oily surface ofChandeleur Sound, Louisiana (see map), on May 6, 2010, two weeks after an explosion at theDeepwater Horizonoil rig sent crude gushing into the Gulf of Mexico.

Oil, gas, and chemical dispersants contaminated thousands of square miles of marine and coastal habitat. Many animals were killed or sickened outright, but on the one-year anniversary of theGulf oil spill, scientists still don't know the extent of the spill's effects on most species.

(See:"Gulf Oil Spill Pictures: Ten Animals at Risk {May 2010.}")

Bottlenose dolphins have been dying in unusually high numbers in northern Gulf waterssince February 2010, two months before the oil spill began, and the trend continues today. Since January, 68 premature, stillborn, or newborn calves have washed ashore.

The Gulf oil spill is certainly on the list of suspects in the recent dolphin deaths, but it's too early to say for sure, Blair Mase, coordinator of the Southeast Marine Mammal Stranding Network of theNational Atmospheric and Oceanic Administration, told National Geographic News in March.

Only a handful of obviously oiled dolphins have been recovered. But a recent study from theUniversity of British Columbiaestimated that the actual number of dolphins and whales killed by the spill could be 50 times higher than official tallies suggest, putting the death toll in the thousands.

—Rebecca Kessler

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Migrating Birds Escaped Worst of Gulf Oil Spill

A year aftertheGulf oil spill, predictions of massbirddie-offs and disrupted migrations have not come true—but oil is still oozing into some bird habitats, experts say.

The timing of the disaster had especially worried scientists and bird-watchers, since it came amid the annual spring migration of tens of millions of birds through the Gulf of Mexico.

(Watchvideo:"Gulf Spill Still Threatens Millions of Migrating Birds.")

"There is still the potential for impacts, but nothing like last year,"said Michael Carloss of theLouisiana Department of Wildlife& Fisheries.

Carloss, who directed the agency's rescue response, hasn't seen any"obvious"changes in migratory patterns or the numbers of birds arriving or passing throughLouisiana—a major bird habitat.

But he describes the damage assessment to wildlife as a"long, arduous process."

(Get more Gulf oil spill anniversary news.)

Breeding Birds May Get Oiled

In the short term, birds in Louisiana may still get oiled by tar balls that are still washing up on beaches and oozing in marsh grasses.

(Read more about Louisiana's embattled wetlands inNational Geographicmagazine.)

Melanie Driscoll, Gulf Coast director of bird conservation for the National Audubon Society, said she's"incredibly dismayed"that oil remains in areas where birds nest and feed in the ongoing breeding season.

Birds can get oil on their feathers and transfer it to eggs or hatchlings, which are especially vulnerable to the oil's toxicity.

With cleanup efforts still under way, the simple act of trying to repair the damage from the oil can actually do more harm.

The small shorebird Wilson's plover is especially susceptible to disruptions, Driscoll said. Cleanup crews have fenced off roads through the grasses that often lie between the birds' nests and their main food sources. Though the birds can squeeze through the fencing, it adds more stress to a bird population that's been declining for decades. (Seevideo:"Citizen 'Scientists' Track Birds in BP-Spill Zone.")

Audubon scientists have also found marine worms burrowing into tar balls in Grand Terre, Louisiana. Lab tests found concentrations of toxic hydrocarbons in the tar balls that could enter the food chain and pose long-term health risks to adult birds or harm developing bird embryos.

Habitat Loss Could Push Birds Over the Edge?

Possibly the most worrying legacy of the spill is the acceleration of habitat loss, scientists say.

For example, some Louisiana bays were hit with heavy oil last summer. The marsh grass that holds the marsh together is dying in many areas—which means that storms, waves, and ship wakes will simply wash away more of the wetlands.

(Seepictures:"Heavy Oil Seeping Into Louisiana Marshes {May 2010}.")

Wildlife& Fisheries' Carloss said it will be difficult to tease out how much habitat loss can be attributed to the spill or the long-standing yearly loss of wetlands from erosion and subsidence. But he says the combination of oiling and cleanup operations in critical marsh habitat clearly must have some effect.

For instance, inLouisiana's Barataria Bay (see map), submerged mats of oily material still send oil ashore nearly every day into many bird species' nesting habitats, Audubon's Driscoll said. (See waterbird pictures.)

For birds flying thousands of miles from wintering spots in the south to nesting sites as far as the Arctic, any loss of shelter, food, and fresh water could leave them too weak to make the journey or diminish their reproductive success when they reach nesting sites.

"A lot of these birds live right on the edge, with an incredibly physically demanding journey,” said David Ringer, Audubon's communications coordinator for the Mississippi River and Gulf of Mexico.

"Anything that goes wrong on the way can push them over the edge."

forNational Geographic News

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Pictures: 20 Surprising Species of the Past 20 Years

Back for an encore after a round of Web stardom as"Yoda bat"last fall,Papua New Guinea's tube-nosed fruit bat has now been named one of the top20 new or rarely seen species encountered during the first 20 years of Conservation International's Rapid Assessment Program(RAP), which launched in 1990.

(Readmore about the tube-nosed fruit bat.)

The RAP expeditions typically send large teams of scientists into remote habitats for intense, monthlong surveys.

"We go out and explore so that we can bring a wide range of new species—1,300 so far—and thousands of other rare and really interesting species to the public and policy makers,"explained RAP director
Leeanne Alonso.

"Showing people what's there helps us make the best decisions about how to manage areas to keep these species around, while continuing the benefits that humans get from these places."

In other words: Help us, they will.

—Brian Handwerk

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Eyes Made of Rock Really Can See, Study Says

When it comes to hard stares and stony gazes, no animal can match the chiton, a small mollusk with eyes made of rock crystal. Now a new study shows just what these strange eyes are capable of.

Scientists had long known that chitons have hundreds of beadlike structures resembling eyes on the backs of their shells. The lenses"are like big, clear pieces of rock,"said study leaderDan Speiser, a marine biologist at the University of California, Santa Barbara. (Related:"Coral Algae Have 'Eyes,' Study Says.")

What's been unclear, however, is if the creatures could actually see using these organs or whether the eyes were good only for sensing changes in light intensity.

"It's been known for over a hundred years that these eyes exist, but no one's really tested what sort of vision they provide,"Speiser said.

His latest research—conducted while he was a graduate student at Duke University in North Carolina—revealed that the sea creatures' eyes are the first known to be made of the mineral aragonite, the same material chitons use to make their shells.

What's more, these stony eyes likely have unique advantages over the squishy eyeballs of other animals.

(Related:"Eyeless Urchins 'See' With Spines.")

Mollusks in Lockdown

To test the chiton's vision, Speiser and his team collected Indian fuzzy chitons(Acanthopleura granulate)from the Caribbean.

When left alone, a chiton will lift part of its oval-shaped body to breathe. But when threatened, the animal will clamp down tightly on the seafloor to protect its soft underbelly.

In the lab, the scientists placed individual animals on a stone slab beneath a white screen, which could change colors. Once the chitons seemed relaxed, the team either placed a black disk directly above the mollusks or changed the color of the background screen from white to gray.

The black disk was designed to simulate a suddenly appearing predator, while the dimming screen mimicked subtle changes in natural light that chitons might experience in the wild—for example, when a cloud passes in front of the sun.

In the experiment, the chitons went into lockdown mode when shown the black disk, but the animals remained at ease when the screen dimmed. This suggests the chiton's eyes are able to distinguish shapes, a prerequisite for true vision.

"The eyes allow the chitons to see objects—not with much detail—but they can distinguish between approaching objects and just decreases in light,"Speiser said.

Speiser estimates chiton vision is about a thousand times courser than human vision, and it's likely they see only in black-and-white. (Related:"Sharks Are Color-Blind, Retina Study Suggests.")

"Even compared to other animals with small eyes, chitons don't see particularly well,"Speiser said.

Rock Eyes Better for Tidal Creatures

Chitons' rock eyes do appear to have some specific advantages. For one thing, the hard aragonite is extremely resilient, an important trait for chitons, which are constantly being pummeled by waves in their natural habitats, shallow tidal pools.

"If their eyes were made of protein"—which is the case for humans and most other animals—"they would get worn right away,"Speiser said. (See"Hammerhead Sharks Have 'Human' Vision.")

For another thing, the experiments suggest aragonite allows the chitons to see equally well in air or underwater, something that's probably useful as tides ebb around the mollusks.

"Behaviorally, the chitons react the same"in both mediums, Speiser said.

That's probably because aragonite has two refractive indices, the extent to which a particular material focuses incoming light. With an aragonite eye, one index creates an image on the eye in water while the other works in air.

Meanwhile, a few mysteries remain about chiton eyes. For instance, it's still not known why only some chiton species have eyes, or how the creatures are able to use the same material to make both their eyes and their shells.

"It's going to be interesting to see how they're shaping these lenses,” Speiser said."How do they make them the right size and shape and keep them translucent? They're exerting some very fine control."

The chiton-eyes research will be detailed in the April 26 issue of the journalCurrent Biology.

forNational Geographic News

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New"Buck-Toothed Evil Spirit" Dinosaur Found

A newly discovered dinosaur species bridges the gap between the earliest known group of predators and more advanced beasts such asTyrannosaurus rex,according to a new study.

Found atNew Mexico's Ghost Ranch fossil site, the primitive dinosaur lived about 205 million years ago. (Relatedpictures:"'Nasty' Little Predator From Dinosaur Dawn Found.")

The dinosaur, which stood as tall as a large dog, boasts a very unusual skull, said study co-authorHans-Dieter Sues, a vertebrate paleontologist at the National Museum of Natural History in Washington, D.C.

"It has a deep, short snout and these monstrous front teeth. That's a kind of skull structure for a predatory dinosaur that's really unexpected for this early point in time,"Sues said.

These features helped earn the new dinosaur the nameDaemonosaurus chauliodus,or"buck-toothed evil spirit"in Greek.

(Also see"'Weird' Buck-toothed Dino Found in China.")

Earliest Dinosaurs Were Survivors

The oldest known dinosaurs lived in what's now South America during the lateTriassic Period, some 230 million years ago. This group included early versions of two-legged predators known as theropods.

But a big gap in the fossil record just after this time led many experts to suggest that these early dinosaurs had simply died out.

"The idea,"Sues said,"was that there was this early diversification of dinosaurs ... but then they went extinct, and more advanced predators took over during the late Triassic and diversified later at the Triassic-Jurassic boundary, when we know that dinosaur predators greatly diversified and increased a lot in size."

Now theDaemonosaurusfind links the two dinosaur groups.

"Our new dinosaur, along with another one that was found a few years ago ... at the same site, indicates that those basal dinosaurs already included a number of early theropods, and that they survived all the way through the Triassic to nearly the beginning of theJurassic Period."

(Seepictures:"New T. Rex Cousin Suggests Dinosaurs Arose in South America.")

Bucktooth Dino Bridges Evolutionary Gap

For nowDaemonosaurusis known only by its fossilized skull and neck vertebrae.

But the fossils show that the dinosaur has several features—including cavities in its vertebrae linked to the respiratory system—that bridge the evolutionary gap between the earliest dinosaurs and the neotheropods, the next group of predatory dinosaurs to evolve.

Finding the dino in New Mexico adds another interesting aspect to the discovery, Sues said.

"We had some inkling that the earliest dinosaurs had made it into the Northern Hemisphere when the supercontinent Pangaea was still in existence and animals could walk around on dry land. But the fossil record was limited to South America,"he said.

"The new find gives further evidence that the earliest radiation of dinosaurs did have a wider distribution, and it is due to the incompleteness of the fossil record that we'd found them only in Argentina and Brazil."

The new dinosaur is described in the April 13 issue of the journalProceedings of the Royal Society B.

forNational Geographic News

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Penguin Numbers Plummeting—Whales Partly to Blame?

Penguin populations have plunged by as much as 50 percent during the past three decades in the West Antarctic Peninsula and Scotia Sea, scientists report.

The problem appears to be a shortage ofkrill, the seabirds' primary fare, caused by rising regional air temperatures and rebounding populations of hungry whales.

Fisheries biologistWayne Z. Trivelpieceof the National Marine Fisheries Service in La Jolla, California, has been monitoring colonies of chinstrap andAdélie penguinssince the mid-1970s.

Because Trivelpiece regularly bands and monitors individual penguins, he's been able to uncover a key factor in the collapse: Far fewer young penguins are surviving their first winter on their own, because they're having a hard time finding krill.

"It's gone from about half of the chicks surviving in the 1970s and mid-1980s to only about one tenth now,"Trivelpiece said.

"And we see from direct measurements of krill that there's about 80 percent less out here than there was just 20 years ago. So the probability of young penguins finding it often enough to survive during those first months of independence is much reduced."

(See"Adélie Penguins Extinct in a Decade in Some Areas?")

Penguins at Risk as Krill Vanish

Krill are tiny, shrimplike animals that live in enormous numbers and represent a large part of the Antarctic food web. Like flocks of herbivores on land, krill feed on single-celled plants called phytoplankton and are in turn gobbled up by many marine predators, including penguins.

The local krill collapse is probably due to a pair of factors, Trivelpiece said.

One is regional air temperatures, which are some 10 degrees Fahrenheit (5 or 6 degrees Celsius) higher than they were in the 1940s and 1950s. Those temperatures drive how much ice forms at the sea surface.

"If the ice no longer forms, phytoplankton in that sea ice aren't available to provide a winter food source for the young krill that spawned the summer before,"Trivelpiece said."Without that food, the young krill don't survive."

(Related:"'Crazy Green' Algae Pools Seen in Antarctic Sea.")

The second krill killer is actually a conservation success story—rebounding populations of whales.

"From what information is available, stocks of krill-eating whales are beginning to return, and their numbers are growing,"Trivelpiece said. (Related:"Whale Hunting to Continue in Antarctic Sanctuary.")

Nineteenth- and 20th-century whale hunts, which severely impacted populations of the giant marine mammals, appear to have ushered in a penguin heyday.

"We don't have good data prior to the 1930s, but it appears that at least the 1930s to the 1970s were a real boom time for penguins, primarily because of the removal of competition in the form of whales."

"Population data from that period is largely anecdotal and provided by the rough counts of British Antarctic workers. But even if you're counting by the seat of your pants, the difference between 100,000 penguins in the 1930s and 500,000 or 600,000 in the 1970s is enormous."

Marine ornithologist Steve Emslie also provided valuable evidence of the boom with his studies of historic penguin colonies. Chemical analyses of old tissue sources, such as eggshells, found that Adélie penguins actually had been fish-eaters before whale numbers dropped.

"Only in the last hundred years or so did krill come into their diet, when the whales were taken out of the system and there was a krill surplus,"Trivelpiece said.

(See"Penguins Changed Diet Due to Whaling, Study Suggests.")

Can Penguins Survive Without Krill?

With krill now dwindling, the previous shift in penguin behavior begs a question: Can the birds simply switch back to eating fish?

"From everything we've seen over a 30-year period, while krill has declined 80 percent, we haven't seen an increase of fish in {penguin} diets,"Trivelpiece said.

"But the fish stocks have also been heavily fished out by Russian trawlers, so we don't even know how much of that prey is available to them at this point."

The penguin-decline study appears in this week's issue of theProceedings of the National Academy of Sciences.

forNational Geographic News

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Alien Wasps Abduct, Drop Ants to Get Food

Looking for a way to banishantsfrom your picnic? According to a new study,waspshave developed a unique method for dealing with the pests: airlifting them away from the food.

In an experiment done with wild insects, scientists inNew Zealandrecently witnessed the common wasp, an alien invader to the island country, competing for food with the native ant speciesProlasius advenus.

When a wasp approached a mound of food swarming with ants, the wasp would pluck an ant from the pile, fly a ways off, and drop the still-living insect from its jaws.

Watch silent video clips of the wasps dropping ants.

"To the best of our knowledge, this behavior has never been described before,"said study co-authorJulien Grangier, a biologist at Victoria University of Wellington.

(Related:"Parasitic Wasp Swarm Unleashed to Fight Pests.")

Wasps Bigger, But Not Badder

Common wasps(Vespula vulgaris)are native to North America but were accidentally introduced to New Zealand in the 1970s. The wasps eat other insects and nectar, capturing live prey or scavenging.

(Related:"Alien-Wasp Swarms Devouring Birds, Bugs in Hawaii.")

Grangier and colleague Philip Lester had suspected that the alien wasps were competing with native ants for scarce protein sources in New Zealand beech forests.

This led the pair to establish an experiment in which ants and wasps were presented with samples of high-protein food: little chunks of tuna fish.

The samples were placed at 48 stations in a natural beech forest, with cameras set up near each one. Both wasps and ants visited 45 of the 48 stations, and the cameras recorded 1,295 interactions between the insects.

In the vast majority of instances, the wasps and ants avoided or ignored each other. However, the researchers documented 341 cases when the ants were aggressive toward the wasps, charging at the larger bugs, biting them, or spraying them with formic acid, a natural defense mechanism.

(Related:"Ants Use Acid to Make 'Gardens' in Amazon, Study Says.")

In just 90 encounters the wasps were the aggressors, including 62 cases of ant dropping. The researchers suspect the other 28 times were ant-dropping attempts that the wasps fumbled.

"It was a surprise to see that ants, being 200 times smaller than wasps, can be serious competitors with them,"Grangier said.

Ant Acid Behind Wasp Behavior?

Most of the time, the wasps' ant-dropping behavior was unprovoked, with ants being simply grabbed and flown away. In a few instances the ants were unruly before they were grappled and carried off.

The team argues that the acid defense may be why the wasps"ant drop"rather than just killing the smaller insects outright.

"By not crushing ants and dropping them away as fast as possible, wasps just protect themselves, avoiding further contact with this harmful substance,"Grangier said.

The wasps' ant-dropping behavior is described in a study published online March 30 by the journalCurrent Biology.

Also see related pictures:"'Zombie' Ants Found With New Mind-Control Fungi">>

forNational Geographic News

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Pictures: Bats Swarm Philippines Cave

On the hunt for their nightly meal, a swarm of Geoffroy's Rousette fruit bats bursts out of aPhilippinescave in 2008.

In January 2011 a U.S. cave-mapping expedition stumbled upon an unusually high number of pregnant bats in the Monfort bat colony, in the country'ssouthern Mindanao region (see map). The bat species does not usually give birth in January, making the discovery a"big surprise"and forcing the scientists to halt their mapping project, according to Norma Monfort, founder and president of theMonfort Bat Cave& Conservation Foundation.

The cause of the bat baby boom is unknown, although Monfort suspects one factor may be that thecaveis protected from humans as an ecotourism site, which allows their numbers to grow. Monfort's family has owned the property for more than a hundred years.

In most of the bats' Southeast Asian range, people either hunt the mammals for food or disturb them while harvesting guano for fertilizer. If people enter a bat cave, nursing mothers can be easily startled, causing their pups to tumble to their deaths, Monfort said by email. (Interactive:Hear bat calls.)

But at Monfort cave, the 1.8-million-strong colony is not only thriving, in 2010 the Guinness Book of World Records deemed it the world's largest gathering of Old World fruit bats.

—Christine Dell'Amore

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Pictures: Millions of Puppy Mummies in Egypt Labyrinth

As part of the first full excavation ofEgypt's ancient Dog Catacombs, scientists examine 2,500-year-old animal remains—a small sample of the roughly eight million animal mummies in these tunnels.

Likely supplied by ancient puppy mills, most of the mummies are dogs, and many were just hours old when taken for mummification, according to new research based on the summer 2010 excavation.

Snaking beneath the desert at the ancient royal burial ground ofSaqqara (map), the Dog Catacombs were discovered more than a century ago. But only now is research shedding light on the massive number of mummies found in this complex of tunnels and chambers dedicated toAnubis (picture)—jackal-headed god of the afterlife.

Poorly mummified and piled high, the carcasses long ago deteriorated into indistinct heaps, experts say.

"It's not easy to identify individual mummies in the galleries or in the photographs,"saidPaul Nicholsonof Cardiff University in the U.K."We have piles of mummy remains just over a meter {three feet} high, on average, that just fill the side tunnels.

"Although the mummies are not well preserved or well decorated, unlike some museum specimens, they can still give us a great deal of scientific information,"Nicholson added.

The mummies were stacked between about the late sixth century B.C. and the late first century B.C., Nicholson said.

(Related:"Dog Mummies Found in Ancient Peru Pet Cemetery.")

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Pictures: Sharks Taught to Hunt Alien Lionfish

Seemingly striking a blow for ecological balance, a Caribbean reef shark chomps on an invasivelionfishin the clear waters ofRoatan Marine Parkoff the coast ofHonduras.

Working with park officials, local divers are attempting to give sharks a taste for the alien reef species, which are native to the Pacific and Indian Oceans. With no natural predators, lionfish populations have exploded throughout the waters of the Caribbean and U.S. Southeast since their accidental introduction by aquarium hobbyists a decade ago.

In Honduras"local dive masters familiar with the sharks decided to try to turn them on to eating invasive lionfish,"said photographerAntonio Busiello, who recently snapped images of the efforts during three months of diving on the site.

"If these predators start to see lionfish as prey, eventually, in time the lionfish may be kept under control as a part of the ecosystem. That was the idea."

—Brian Handwerk

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Pictures: Trees Cocooned in Spider Webs After Flood

Trees shrouded in ghostly cocoons line the edges of a submerged farm field in thePakistanivillage of Sindh, where 2010's massivefloodsdrove millions of spiders into the trees to spin their webs.

Beginning last July, unprecedented monsoons dropped nearly ten years' worth of rainfall on Pakistan in one week, swelling the country's rivers. The water was slow to recede, creating vast pools of stagnant water across the countryside. (See pictures of the Pakistan flood.)

"It was a very slow-motion kind of disaster,"said Russell Watkins, a multimedia editor with the U.K.'sDepartment for International Development(DFID), the organization tasked with managing Britain's overseas aid programs.

According to Watkins, who photographed the trees during a trip to Pakistan last December, people in Sindh said they'd never seen this phenomenon before the flooding.

(Seepictures:"World's Biggest, Strongest Spider Webs Found.")

—Ker Than

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Photos: Dams Threaten Mekong River Megafishes

This gallery is part of aspecial news series on global water issues.

Thegiant freshwater Mekong River stingrayis just one of many megafish species that could be threatened by ambitious dam-building plans in the Mekong River Basin.

(Read the full story.)

The outcome of a meeting last week among four Southeast Asian countries could determine whether construction of the first of 11 controversial dams on the Mekong River can proceed.

The dams are designed to generate electricity for the region, but environmentalists fear they will disrupt the Mekong's delicate freshwater ecology, which supports dozens of other critical species, and that they will threaten local communities who rely on the river for food and jobs.

This giant fish, found near the Cambodia-Vietnam border in 2002 by National Geographic Emerging ExplorerZeb Hogan, measured 162 inches (413 centimeters) from nose to tail.

(Read more in“GIANT STINGRAY PICTURE: Largest Freshwater Fish?” andwatch video of this enormous species.)

—Tasha Eichenseher and Ker Than

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April Fools'Day Pictures: Six Animal Hoaxes

A woman examines"A Young Family,"a sculpture of a human-like pig and her offspring by Australian artistPatricia Piccinini, at the 50th Venice Biennale of Art in June 2003.

Photographs of the sculpture circulated on the Internet in years afterward with messages suggesting—among other things—that the pictures depicted a human-dog hybrid created by an experiment gone wrong, according to the rumor-squashing websiteSnopes.com.

The human-dog hybrid is one of many animal hoaxes perpetrated over the centuries—especially asApril Fools' Daypranks.

As it turns out, there's actually some human in the sculpture—Piccinini used human hair along with silicone, acrylic, leather, and timber as materials for the artwork, according to her website.

In real life,scientists have already been blurring the line between human and animal by producing chimeras—hybrid creatures that are part human, part animal, National Geographic News reported in 2005. For instance, scientists at the Shanghai Second Medical University in 2003 fused human cells with rabbit eggs—reportedly the first human-animal chimeras successfully created.

(Also see:"April Fools' Day Pictures: Four Historic Science Hoaxes.")

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Radiation in Japan Seas: Risk of Animal Death, Mutation?

If radioactive material from the Fukushima Daiichi nuclear power plant—disabled by the March11Japan earthquake and tsunami—continues to enter theocean, marine life could be threatened, experts say.

(See relatedphotos:"Japan Tsunami: 20 Unforgettable Pictures.")

In the past week, seawater samples taken near the nuclear power plant, onJapan's eastern coast, have shown elevated levels of radioactive isotopes, including cesium 137 and iodine 131, according to theNew York Times.(See"Japan Tries to Avert Nuclear Disaster.")

All life on Earth and in the oceans lives with exposure to natural levels of ionizing radiation—high-frequency radiation with enough energy to change DNA. Most such genetic damage heals, but the addition of human-made radiation can make it harder for the body to repair broken genes.

Radiation concentrations in the Japanese seawater samples have fluctuated in past days, but on Wednesday the amount of iodine spiked to 3,355 times the legal limit for seawater, Japanese nuclear safety officials told the Associated Press.

That level is the highest so far—and an indication that more radiation is entering the ocean, though how is still unknown, the agency reported. Cesium was also found to be 20 times its safety limit on March 28, according to theTimes.

Radiation Can Cause"Bizarre Mutations"

Once in seawater, radiation can hurt ocean animals in several ways—by killing them outright, creating"bizarre mutations"in their offspring, or passing radioactive material up the food chain, according toJoseph Rachlin, director of Lehman College's Laboratory for Marine and Estuarine Research in New York City.

"There will be a potential for a certain amount of lethality of living organisms, but that's less of a concern than the possible effects on the genetics of the animals that become exposed,"Rachlin said.

"That's the main problem as I see it with radiation—altering the genetics of the animal and interfering with reproduction."

Even so, according to radioecologistF. Ward Whicker, the concentrations of iodine and cesium levels"would have to be orders of magnitude larger than the numbers I've seen to date to cause the kind of radiation doses to marine life that would cause mortality or reductions in reproductive potential.

"I am very doubtful that direct effects of radioactivity from the damaged reactors on marine life over a large area off the coast of Japan will be observed,"Whicker, professor emeritus at Colorado State University, said via email.

Likewise, using legal limits to gauge damage to marine life is of little value right now, he said.

To make a"credible assessment"of the risk to marine animals, scientists would have to know the actual concentrations of radioactive iodine in the water and fish or other marine animals off Fukushima Daiichi, he said.

Radiation Hardest on the Little Ones

It's possible that levels of radioactive contamination near the Fukushima nuclear reactors could increase and cause some harm to local marine life, Whicker said.

"If this happens, the most likely effects would be reductions in reproductive potential of local fishes. ... ,"he said.

Marine organisms' eggs and larvae are highly sensitive to radiation, since radioactive atoms can replace other atoms in their bodies, resulting in radiation exposure that could alter their DNA, Whicker said. (Get the basics on genetics.)

Most such deformed organisms don't survive, but some can pass abnormalities on to the next generation, Lehman College's Rachlin said. Either way, the radiation exposure could hurt the population's ability to survive long-term.

Rachlin thinks the most susceptible critters would be soft-bodiedinvertebratessuch as jellyfish, sea anemones, and marine worms—which can take up the radiation more quickly than shelled creatures—though Whicker said fish may be most at risk.

Whicker added,"I would expect any temporary losses in reproduction in local fish to be offset by immigration of unaffected individuals from surrounding areas that would be impacted to a lesser degree."

(See"Chernobyl Birds' Defects Link Radiation, Not Stress, to Human Ailments.")

In addition to its threats to reproduction, pockets of radioactive material can can burn fish passing through, hitting them like a stream of searing water, Rachlin said.

Complicating matters is the fact that predator species in the Pacific such as tuna and sailfish are already stressed byoverfishing, according to Rachlin.

"I'm concerned—this is the spawning season. ... If this impacts the survivorship of the young and larvae, this will be a further insult."

Radiation Threat Here to Stay?

According to chemical oceanographerBill Burnett,"In the short run {the radiation} could have some definite negative impacts"on marine life.

"The good news is the half life {of iodine} is only eight days,"added Burnett, an expert in environmental radioactivity at Florida State University.

So"if they stop the source of radioactive leakage, this is going to be a short-term problem."

However Fukushima Daiichi's leaking cesium is potentially more serious, since that isotope takes 30 years to decay, Burnett said.

Radiation Can Travel Up the Food Chain

There could also be some movement of radiation up the food chain if animals eat irradiated plants and smaller, radioactive animals, Rachlin said.

In particular, plants such askelpcan quickly absorb iodine, FSU's Burnett said. (See pictures of ocean wildlife.)

There's a possibility that the devastation of towns in northeastern Japan caused by the earthquake and tsunami also released toxic metals such as lead into the soil and water, according to Texas Tech University ecotoxicologistRon Kendall.

Previous studies have shown that metals can work in concert with radiation to suppress immune systems in vertebrates, making them more vulnerable to disease, Kendall said.

It's a"big issue for the environment and human health because of the widespread destruction. It takes me back to New Orleans after Hurricane Katrina—this to me is even more complicated with the radiation."

(Seephotos:"Japan Reactor Crisis: Satellite Pictures Reveal Damage.")

Ocean Resilient Against Radiation

The ocean has a"tremendous capacity"for diluting radiation, Colorado State's Whicker noted.

"It also has resilience, in the sense that the area would recover over time as the situation improves and as the radioactivity decays and disperses."

"But I should caution that we have not had much opportunity to study the effects of very large releases of radioactivity into marine ecosystems,"he said. The best data comes from nuclear weapons tests in the Pacific in the 1950s and 1960s.

Texas Tech's Kendall also pointed out that there's not much known about radiation in seawater.

"The dose makes the poison,"he said,"and the more concentrated the radiation, the more potential effects. It's something we definitely need to monitor."

Added Lehman's Rachlin:"If it's a one-shot pulse, OK, not a problem.

But if the radiation leaks continue for several months, Japan may be dealing with a more serious blow to marine life, he said.

The coastline, after all, isn't Chernobyl, he said."We can't cement {over} that whole area."

National Geographic News

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"Castrated" Spiders Are Better Fighters, Study Says

Although emasculated spiders can no longer be lovers, they are better fighters, a new study says.

In many spider species, males have sex using two appendages known as pedipalps. But males will often lose one or both pedipalps during the act—behavior that might seem like a bad idea evolutionarily, since it renders the male sterile.

(Relatedpictures:"'Torture' Phalluses Give Beetles Breeding Boost.")

Scientists have proposed that such genital amputation plugs up a female to help ensure that other males don't successfully impregnate her.

To learn more about why male spiders become eunuchs, scientists examined the mating behaviors of the Southeast Asian orb web spider,Nephilengys malabarensis.(Related:"Largest Web-Spinning Spider Found.")

The scientists found that amputated genitals effectively plugged up a female spider 75 percent of the time. In addition, the team saw that males with missing genitals were far more aggressive and active in guarding females.

During contests between males, full eunuchs that had lost both pedipalps were better fighters than half eunuchs and intact males, the study showed. Overall, the eunuchs were more than three times more likely to attack, chase, and defeat any rivals.

The scientists think that, once a male has lost his means of procreating, he protects his investment further by becoming a superwarrior.

"We think, but are not sure, that the changes in behavior may be due to changing hormone levels"triggered by losing the pedipalps, said study co-author Matjaž Kuntner, a spider expert at theSlovenian Academy of Sciences and Artsin Ljubljana.

"But the ultimate reason for this behavior is that eunuchs, with no reproductive future, have nothing to lose and risk more in contests."

The study also observed that females of this species will frequently devour males after sex, Kuntner added. Males could thus be breaking off their genitals, he said, to help ensure their sperm still has a fighting chance even if they fall victim to cannibalism.

The eunuch-spider study was published online March 23 in the journalAnimal Behaviour.

forNational Geographic News

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