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Why do we yawn? : While this sounds like a question which has been answered already, the real reason is still a hypothesis. Yawning helps to get oxygen into our bloodstream and makes us more awake. Right? Wrong. It has nothing to do with Oxygen at all. Read on...

Radiator cooling : When our bodies are hot, standing in front of a fan can be a quick fix, and the brain is the same way. When we yawn, we pull in cool air through the nasal and oral cavities, and that air comes in contact with all of the blood vessels in those densely packed areas. Many of those blood vessels carry blood directly to the brain, and the surge of air cools the blood, and thus the brain.

Catching a yawn : Why are yawns so contagious? Does the fact that we catch them from one another shed light on their underlying function? One possibility is that contagious yawning serves as a way of showing empathy. While all vertebrate mammals experience spontaneous yawning, only humans and our closest relatives, chimpanzees, seem to experience the contagion effect—a sign that there may be a deeper social meaning to the experience. What’s more, while spontaneous yawning occurs in the womb, contagious yawning develops only later in life, as does empathy. Children younger than five don’t yawn any more often when watching videos of yawns than they would normally.

Bigger brains mean longer yawns : Yawning—a stretching of the jaw, gaping of the mouth and long deep inhalation, followed by a shallow exhalation—may serve as a thermoregulatory mechanism, says Andrew Gallup, a psychology professor at SUNY College at Oneonta. In other words, it’s kind of like a radiator. In a 2007 study, Gallup found that holding hot or cold packs to the forehead influenced how often people yawned when they saw videos of others doing it. When participants held a warm pack to their forehead, they yawned 41 percent of the time. When they held a cold pack, the incidence of yawning dropped to 9 percent.

H/t to +Amanda Powter for asking this question

References and links

#yawn   #science  

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Physics behind the wet dog shake : While we see this often in dogs, many mammals use physics to dry off quickly. The super slow motion reveals how it happens, but the mathematics and fluid dynamics support what size dog shakes at what speed to expend the least energy.

Shaking it off : Dickerson, along with some colleagues from the Georgia Institute of Technology, has written “The Wet-Dog Shake,” published in Fluid Dynamics. They attempt to calculate the optimum speed at which dogs should shake to most efficiently dry their fur.

The team built a mathematical model of the processes involved, reasoning that surface tension between the water and the dog’s hair is what keeps the dog wet. Overcoming that tension requires a centripetal force that exceeds it. As centripetal force varies with distance from the centre of the creature, its radius is therefore crucial to work out the speed of the oscillations. The team arrived at an equation that calculates the frequency of that oscillation.

The scientists determined that shaking begins at the head area, which provides a solid point for the energy wave to propagate down the animal's body. The head can also twist more, resulting in higher amplitude waves. Once that process starts, the animal's head, body and skin all move during a shake. The body, though it shakes at the same frequency of the skin, cannot rotate as far, though the skin effectively twists around the body, traveling faster than the body and head can move.

Very furry animals tend to have especially loose skin, which whips around as the animal changes direction, increasing the acceleration. Dickerson said it's comparable to someone cracking a whip. He and his team discovered that animals with smaller bodies must shake more rapidly than larger animals. These tinier mammals can experience up to 20 g's of acceleration. The chosen frequency of animals might even be unconsciously determined, based on nerve and muscle dynamics.

References and links

#fidofriday   #science  

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The Elephant Alarm for Humans : African elephants have a signal for humans. And it spells trouble. Studies show that elephants react quickly to human voices, becoming more vigilant and running away from the source of human sounds. But we already knew Elephants had a vocabulary. ....

Study shows how elephants react : Researchers from Oxford University carried out a series of audio experiments in which recordings of the voices of the Samburu, a local tribe from North Kenya, were played to resting elephants. The elephants quickly reacted, becoming more vigilant and running away from the sound whilst emitting a distinctive low rumble. When the team, having recorded this rumble, played it back to a group of elephants they reacted in a similar way to the sound of the Samburu voices; running away and becoming very vigilant, perhaps searching for the potentially lethal threat of human hunters.

Is it language? : Lucy explains: 'Interestingly, the acoustic analysis done by Joseph Soltis at his Disney laboratory showed that the difference between the ''bee alarm rumble'' and the ''human alarm rumble'' is the same as a vowel-change in human language, which can change the meaning of words (think of ''boo'' and ''bee''). Elephants use similar vowel-like changes in their rumbles to differentiate the type of threat they experience, and so give specific warnings to other elephants who can decipher the sounds.'

References and Sources



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Animal doctors : No really. This is not a post about vets. This is about how animals self-medicate.... including parrots, dogs, cats, chimps, elephants and a host of other creatures. There is even a word for it. Zoopharmacognosy is derived from zoo which means animal, pharma  which stands for drug and gnosy, which means knowing. Next time you see your dog or cat eating grass, you know it's a part of their self-medication regime.

Neighbourhood pharmacy : Bears, deer, elk, and various carnivores, as well as great apes, are known to consume medicinal plants apparently to self-medicate. Some lizards are believed to respond to a bite by a venomous snake by eating a certain root to counter the venom. Baboons in Ethiopia eat the leaves of a plant to combat the flatworms that cause schistosomiasis.

More widespread than one would assume : Birds, bees, lizards, elephants, and chimpanzees all share a survival trait: They self-medicate. These animals eat things that make them feel better, or prevent disease, or kill parasites like flatworms, bacteria, and viruses, or just to aid in digestion. Even creatures with brains the size of pinheads somehow know to ingest certain plants or use them in unusual ways when they need them. Anyone who has seen a dog eat grass during a walk has witnessed self-medication. The dog probably has an upset stomach or a parasite.

Cats may be eating grass for nutrients : In particular, a nutrient that grass provides for cats is folic acid. This is a vital precursor for your cat's ability to synthesize hemoglobin. Hemoglobin is what supplies your cat's organs with oxygen. We all know oxygen is pretty important.

Other examples : Red and green macaws, along with many animals, eat clay to aid digestion and kill bacteria. Pregnant lemurs in Madagascar nibble on tamarind and fig leaves and bark to aid in milk production, kill parasites, and increase the chances of a successful birth. Pregnant elephants in Kenya eat the leaves of some trees to induce delivery.

How does one determine if an animal is self-medicating? : Huffman established widely used criteria for judging when an animal is self-medicating. First, the plant eaten cannot be a regular part of the animal’s diet; it is used as medicine not food. Second, the plant must provide little or no nutritional value to the animal. Third, the plant must be consumed during those times of year—for example, the rainy season—when parasites are most likely to cause infections. Fourth, other animals in the group don’t participate. If the activity meets these standards, it is safe to assume the animal is self-medicating, Huffman says. Researchers have observed the practice in 25 regions involving 40 different plants.

Learned behavior? : The obvious question is how do the animals—some of them not noted for intelligence—learn to do this? How did sparrows and finches learn to collect nicotine-heavy cigarette butts to reduce mite infections in their nests? How do honey bees and wood ants know to line their nests with resin to combat bacteria? We don't know for sure, but there is a strong hypothesis.

Article Link:

News article:

Wikipedia link:

Pic courtesy:

Related TED event:

Research paper: Huffman M. (1997) Current evidence for self-medication in primates: A multidisciplinary perspective. Yearb Phys Anthropol 104(suppl 25):171–200.

#science #scienceeveryday  

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Insects benefit from following the leader : While we often talk about leadership in the human context, scientists have discovered that in the case of the Sawfly larvae, they actually benefit from following a leader. Not only do the followers benefit, but the leader does as well - and they do this all democratically! Swarm behavior has always fascinated me, and some of the things we learn about insects is quite interesting...

Social behavior : Scientists have shown for the first time that when insect larvae follow a leader to forage for food, both leaders and followers benefit, growing much faster than if they are in a group of only leaders or only followers. The work gives new insight into why such social relationships evolve in insects, and why they are maintained. The study looked at larvae of the iconic Australian steel-blue sawfly Perga affinis often known as 'spitfires'. Sawfly larvae can grow to 7cm long and forage nocturnally in Australian Eucalyptus trees, forming large groups that can strip all of the leaves from a tree in a few days.

Leadership and followership works : "We see that leaders only benefit from being leaders if they have followers, and that followers only benefit if they have leaders. There is no use being a shepherd without sheep or sheep without a shepherd." Study co-author Professor Mark Elgar said that while leaders do not differ in growth rates or weight, they may acquire other benefits such as lower predation or enhanced immune function. "The next stage of our research is to find out how certain larvae become the leaders in a group and how they are communicating directions and encouragement to their followers," added Prof Elgar.

Democratic leadership : Sawfly societies operate democratically, with leaders and followers co-operating to decide on group movements. This contrasts with other animal societies, such as baboons and wolves, where leaders are despotic, dominating their followers. Ms Hodgkin, a PhD candidate at the University of Melbourne said the team was keen to understand why the larvae followers allow others to determine the group's movements.

Speed boost : Destin, of the YouTube video series Smarter Every Day, and Phil Torres, who’s a conservation biologist and intrepid rainforest explorer, come across this large, writhing ball of caterpillars in the Amazon rainforest. And seemingly immediately, Destin has an idea – what if the reason that the caterpillars are crawling over each other is to get a speed boost? So he goes home, and designs a wonderfully elegant experiment, using Lego, to prove his point. I just love how this simple Lego powered explanation gets right to the heart of this strange phenomenon.

Article link:

Additional source:

Reference :


Pics courtesy: sciencedaily, wired, and

#science #scienceeveryday  
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Metamorphosis : The Science of the changing body plan. Metamorphosis is a change in the body structure of organisms (usually rapid) involving cell growth and differentiation. It is fascinating to study and even more so to see it in action. The process is quite gruesome, and there is a good reason why very small kids are not told how a caterpillar transforms into a butterfly. The primary role of metamorphosis seems to be to have a different ecological niche for larval forms and adults. It may all be about survival....

Caterpillars; the inside story : If you look inside a caterpillar you won't see a butterfly all rolled up waiting to emerge. You'll just see more caterpillar and some well-chewed leaves. But with a decent microscope and some excellent navigation skills you might glimpse some tiny disc-shaped bags of cells here and there. They're called imaginal discs, and once the caterpillar silks itself up in a chrysalis they kick into action, each one of them growing into an antenna, eye, wing or other butterfly bit.

Eating it's own tissue : During the week or two spent in its chrysalis (pupation) the caterpillar gradually digests all of its own tissue, releasing the nutrients that all those imaginal discs then use to grow into butterfly wings, legs, feelers and the rest. It's the ultimate in recycling makeovers, and it's due to some interdependent hormonal changes that make puberty look like a doddle.

Hormones control the process : The thing that drives caterpillars (and other flying insect larvae) to stop feeding their faces, settle down somewhere safe, and pupate, is the hormone ecdysone. It's the same hormone that causes the larvae to moult each time they outgrow their current skin. The reason this final moult into a butterfly is so different from the earlier ones is because the level of another hormone; juvenile hormone; is suddenly lower.

Juvenile hormone is the great controller of metamorphosis, by delaying it until the caterpillar has moulted and grown enough to produce a decent-sized butterfly. It works by blocking the genes in the imaginal discs, keeping those wannabe butterfly cells in a holding pattern. So while juvenile hormone is being pumped out of tiny glands behind the brain, all the caterpillar can do is feed, grow and — when instructed by ecdysone — moult. (It's so good at preventing larvae from maturing that a lot of insecticides have been based on artificial juvenile hormone).

A complete makeover : Butterflies are pretty and all, but that's not the only pay-off for all that metamorphic effort. Butterflies and caterpillars don't just look different; they've got different ideas of what constitutes food and accommodation. While caterpillars live off leaves and are plant-bound, those butterflies that do feed only drink nectar, and they can fly from place to place looking for love and somewhere to lay the progeny. Those fundamental differences mean the adults don't compete with the juveniles for food or habitat, so the species has a better shot at making it. Which probably goes a long way towards explaining why more than half the animal species on the planet are insects that undergo the same kind of complete metamorphosis. As far as evolutionary strategies go, it's gold. And come mating time it doesn't hurt that the adults are almost always better lookers than all those larvae that only a mother could love.

Article source:

Bacteria play a role in metamorphosis (Butterfly Microbiome):

Paper (related):

Wikipedia link:

+Scientific American article:

3D Scan of a chrysalis:

Additional link:

Earlier post on the Axolotl:

Pics courtesy :, and the  +National Geographic  link above.

#metamorphosis #scienceeveryday #sciencesunday  
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Flight of the Falcon ....... no, the Robohawk? : This clumsy title was what I actually thought when watching the video. Clear Flight Solutions has created a robotic bird to scare off other birds especially around airports. I was a little taken aback at how realistic it is, using wing deformation to glide, just like a real bird.

The genesis : Nijenhuis is a student of applied physics and fluid dynamics at the Technical University of Twente in the Netherlands. When wings are fixed, we're fine. We can run tests and calculate forces and as a result have been able to develop planes that take us all over the globe. "But the minute wings start moving, we really have a problem," Nijenhuis says. "It's all about very complex, three-dimensional flow. What a bird actually does is so complex that it's incredibly difficult to mimic."

Creating the Robohawk : The big concept ended up being flexibility. Instead of just flapping from one joint like a rigid two-by-four, bird wings deform across their entire length as they move through the air. For the Robirds, Nijenhuis complemented the basic hinging motion with a pitching motion on the wing tips -- the further outward you go, the more the heavy-duty foam wings deform upwards and downwards. The result, when paired with some on-board sensors and sophisticated stabilisation software, is a fairly convincing approximation of bird flight.

Why is it important to fly like a bird : Getting close to the mark is important for the Robirds to do their job. Nijenhuis says two things are needed to trigger birds' flight instinct: a silhouette and wing movement. "If it doesn't look like a predator, they don't care. And if it doesn't move like a predator, they don't care either."

Article source:

Link to company details:

Company website:

Earlier version of a 'scarecrow' hawk :

#robotics #hawk  

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Flying Snails : No not really. But this is a kind of an amusing story. It all started with Charles Darwin, who was fascinated that how very similar snails were found on diverse land masses. It was hypothesized that snails stick to birds. Some snails managed to hitch rides on logs or other floating items. But some snails have a slightly different method of travelling. Read on to know more.

Horn snails : The horn snails found their own life rafts: shore birds. Although the research group can't prove that the scenario is true, they think it could have gone like this: Nearly 1 million years ago, a wading heron gobbled a basking Pacific horn snail, shell and all. Luckily for this intrepid explorer, armored invertebrates can survive for days in the bellies of shore birds. Snug inside its unsuspecting taxi, the snail soared high above what was likely Mexico before being excreted in the Atlantic Ocean—a journey of about 200 kilometers or more. (From Sciencemag :

Tough travellers : If a bird takes flight and keeps aloft for all five hours, a snail could be transported as far as 186 miles away. Should the snails take hold in their new homes, and should ducks sample the new population of gastropods, the snails could be dispersed even further still. Why the one species of snail was able to survive while the other three perished is not immediately clear. But van Leeuwen and co-authors suspect that the pre-existing adaptations of Hydrobia ulvae were key. The strong shell and other traits possessed by the snail species – thought to be defenses against predation and drying out when exposed – may better protect these snails from being crushed or killed by enzymes in duck digestive tracts. The snails just happened to have a suite of traits which allowed them to survive the internal journey. (From +WIRED :

Globetrotters : Plants and sedentary animals have long travelled great distances thanks to water, wind, or hitching a ride on other, more mobile animals. But the enormous distances travelled by these snails more commonly occurs in the plant than in the animal kingdom. Preece is now trying to collect molecular data as further evidence of globetrotting in these snails, beyond the Atlantic region. He points out that past research has also shown the creatures doing some mountaineering: they were found on a remote mountain peak on Madeira Island, Portugal, back in 1921. "They get around the world," says Preece. (From +Nature Publishing Group :

Related research paper:

Additional link:

Main research paper:

Pic Courtesy :

#snails #travel #scienceeveryday  

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Not just a predator, Terminator level achieved : The red lionfish ( Pterois volitans ) was assumed to be a just another predatory fish. Since it is an invasive species, it often decimates local fish populations. However, researchers have found that unlike most other predators, they do not move if their prey species dwindle and prey are harder to find. They actually wipe out the prey species to local extinction.... a very Terminator-like behaviour.

Article Extract: The finding of behavior that was called “alarming” was presented today by Kurt Ingeman, a researcher from Oregon State University, at the annual meeting of the Ecological Society of America. The new research concludes that lionfish, by comparison, appear to stay in one area even as the numbers of prey diminish, and in some cases can eat the population to local extinction. They have unique characteristics that make this possible, and like the terminator, they simply will not stop until the last of their prey is dead.

The lionfish invasion in the Atlantic Ocean is believed to have begun in the 1980s and now covers an area larger than the entirety of the United States. Ingeman’s adviser, Mark Hixon, and fellow graduate students have shown that lionfish can wipe out more than 90 percent of the native fish in some hard-hit areas.

The arsenal : The Red Lionfish is a venomous coral reef fish. As with many species within the Scopaenidae family, it has large, venomous spines that protrude from the body, similar to a mane, giving it the common name lionfish. The venomous spines make the fish inedible or deter most potential predators.

Article Link:

Additional link:


Wikipedia link:

Related paper:

Additional paper:

#scienceeveryday #lionfish  

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Far from Blind : We already know that despite the tiny size of the bat's eye and its nocturnal behavior, none of the species of bats is blind. I have been fascinated by bats (Order Chiroptera) from the time I was in school... it's outlier superpowers (I use the word loosely) for a mammal has been a source of interest to me. Recent studies show that bats have more in their arsenal than one imagined. Read on to know more.

Bats use polarized light: Biologists in Germany and the UK moved some female greater mouse-eared bats around at sunset to demonstrate that they use polarized light to calibrate their internal compasses. The nocturnal animals calibrate themselves when they’re gearing up to be active, and this enables them to fly in the right direction when in search of food. If you could see these patterns, they would look like bands of light stretching 90 degrees away from the sun, across the zenith (top of the sky) and heading 90 degrees west. As you get very close and very far from the sun, the patterns are a little weaker. Like birds, bats apparently look at these patterns and use them to calibrate their magnetic compass.

What is Polarized light?: Polarized light is a characteristic of light bouncing around in Earth’s atmosphere. Water droplets, dust, airborne particles, and the air itself scatter light from the sun (literally why the sky is blue), but this scattering follows a defined pattern. The patterns depend on where the sun is in the sky. Polarization patterns are harder to distinguish during the day when the sun is high in the sky, and are much stronger at sunset and sunrise, when the sun is closer to the horizon.

How do they do it? : It’s not clear how the bats discern the polarized light, but it may be related to the type or alignment of light-detecting pigments in their retinas, the team suggests. The bats may have evolved to reset their navigation system using polarized light because that cue persists long after sunset and is available even when skies are cloudy.

Researchers have found that certain insects, birds, reptiles, and amphibians can also navigate using polarized light.

Other superpowers: Echolocation : To track down prey, avoid predators and find their way home in the dark, most bats depend on echolocation. They broadcast high-pitched sonar signals and listen for the echoes of sound waves bouncing off objects they’re looking for or obstacles in their path. Bats’ brains then process the auditory information within those echoes as visual maps. Scientists know a lot about the finer points of how echolocation works, but they differ on whether that sense evolved before or after bat’s ability to fly.

Source Article:

Sciencemag link:

Wired reference:
What is polarization of light (ref) :

Polarization waves:

Related link (How to detect polarized light) :

Discovery link:

Batfacts from Smithsonian:

Pics links and attribution: Animated gif link:, Pic on polarized light (Wikipedia) - The effects of a polarizing filter (right image) on the sky in a photograph, Main pic courtesy :

#scienceeveryday #sciencesunday #bats
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