Many animal appendages, such as legs, tails, beaks, or ears can be used to dissipate excess body heat. Because of this cooling function, these body parts generally have a larger surface area relative to their volume for mammals and birds that live in warmer climates than for such animals that live in colder climates. This principle of animal form is called ‘Allen’s rule’ after its discoverer; the American zoologist Joel Allen.

In 2021 a team of Australian and Canadian researchers published a review summarizing evidence that many mammal and bird species are changing the shapes of their bodies over time, in accordance with Allen’s rule, to cope with the warmer climate resulting from human-caused global climate change. The evidence is particularly pronounced for several species of Australian parrots. The relative sizes of the bills of these birds have increased by four to ten percent between 1871 and the present. This increase occurred in step with increasing summer temperatures.

Similar changes were found in numerous other bird species, including the dark-eyed junco, a North American bird. The bills of birds are especially important for removing heat because they are rich in blood vessels and aren’t insulated by feathers. In mammals, legs, tails, ears, and bat wings play a similar role in heat dissipation because they are likewise rich in blood vessels and not insulated by fur.

The researchers noted corresponding increases in the relative sizes of these body parts for a variety of mammals including shrews, mice, and bats. In ongoing work, the researchers are extending their analysis to more species and habitats. The research highlights the serious ecological consequences of human-caused global climate change.

Reviewer: Ryan Long, the University of Idaho

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Today's moment of science is inspired by the plethora of crime dramas. How do the one-way mirrors we see in these shows so often actually work?

The trick is simpler than you might think. Most mirrors are made by applying a thin layer of a reflective material, aluminum in most cases, to the back of a sheet of glass. This is called back silvering, and it makes the glass opaque. When we look in a mirror, our image is reflected by the aluminum, which is made more durable by its glass covering.

So, one-way glass isn't fully silvered. The reflective material is applied less densely. This is called half-silvering. The effect is that the glass is not completely opaque like a traditional mirror. About half the light striking the glass passes through it, and the other half is reflected.

So far, people on both sides would see the same thing: fractured images of both themselves and the people on the other side.

Now for the second trick to one-way glass: the lighting. The room the suspect is in is kept bright, so that the reflective quality of the glass prevails. The room on the other side of the glass is kept dark, so that instead of their reflections, the detectives see what is illuminated on the suspect's side of the glass: the suspect.

But, if the light were to be turned up on the detective's side or turned down on the suspect's side, the magic would fizzle, and glass would become a window for both parties.

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We don’t usually think of friends in terms of what advantages they give us, although, if asked, most people would probably say that their friends add a lot to their lives.

Scientists view friendship among animals in slightly starker terms: if strong social bonds exist between animals, it probably means such ties directly benefit the animals in some way. A team of researchers set out to find out whether the benefit of friendship between male chimpanzees may be to further a goal that many animals share—more offspring. 

To do that, they examined genetic and behavioral data of a group of chimpanzees in Tanzania. They found that males who had a larger number of social ties with other males did tend to have more offspring. Males with at least two social ties to other males were over 50% more likely than other males in the dataset to have had any given offspring.

Previous research has shown that animals that form more coalitions—two or more individuals join to act aggressively towards a third—rise in rank and have more offspring. The team thinks that males who form more social bonds may be more likely to form coalitions, which could be why they’re also observed to have more reproductive success. The team also looked at what effect social ties to an alpha male had, and found that friendship with an alpha male also increased a male chimp’s chance of having an offspring.

What’s interesting is that social bonds with either multiple males or with an alpha male can lead to reproductive success. Male chimps don’t necessarily have to have friends in high places, they just need to have friends.

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• ScienceDaily - Building bonds between males leads to more offspring for chimpanzees

Are you a twin? No, well are you sure?

You could be a twin, but the twin is within, or a chimera.

A chimera is a mythological beast with the head of a lion, the body of a goat, and the tail of a dragon. However, in biology a chimera is an organism made up of two distinct genetic lines.

It's what happens when twin embryos fuse in the womb. The fusion results in what looks like a single embryo, but the genetic material from each twin remains separate.

What does that mean? Does a chimera have one arm from one twin and the other arm from the other twin?

Well, it's something like that. It's not like the arms would look different, exactly, or that the body's organs wouldn't be compatible or not work properly.

However, they do contain different and distinct sets of chromosomes. If you're a chimera, your liver could be composed of cells with one set of chromosomes while your heart, say, consists of cells with an entirely different set.

" Chimera (Genetics)." Wikipedia. Re-accessed for re-run on July 30, 2018.

Animals are made mostly out of water, and of complex molecules centered around carbon atoms. But they also contain a surprising range of other substances, which give their parts useful special properties.

The mandibles of ants are incredibly sharp and durable cutting tools. Leaf-cutting ants live in the tropics and cut the leaves of plants into tiny pieces with their razor-sharp mandibles. They take the pieces back to their anthill to cultivate a nutritious fungus. When the ants are threatened, those same tiny but powerful mandibles can easily slice and puncture human skin.

Ant mandibles and the cutting and piercing body parts of other insects, spiders, and scorpions are made of proteins and carbohydrate polymers. They are also distinctively rich in metals such as zinc and manganese. The metals appear to be the source of their special properties. In 2021 a team of American researchers published new findings that tell us how metals give these animal ‘tools’ their cutting and piercing power.

The researchers studied the cutting edge of an ant mandible with a technique called atomic probe tomography. This allowed them to map the mandible all the way down to the positions of its individual atoms. They were surprised to find the zinc atoms weren’t grouped into tiny lumps, but were instead spread uniformly through the atomic structure of the mandible.

They think this organization is the source of its precision, sharpness, and durability. The material allows the ant to puncture and cut using only sixty percent as much force as it would need if it used bulkier materials like those in human teeth. The researchers’ hope their studies will help engineers make new materials for human use.

Reviewer: Paolo S. Segre, Hopkins Marine Station, Stanford University

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Curiosity killed the cat, but there’s no indication that it has the same effect on humans. 

Curiosity in babies helps them learn about the world and might even predict future cognitive abilities. That’s why scientists wanted to know whether moments of curiosity that babies exhibit are random variations, or whether they indicate a characteristic of the particular baby that carries into their later years.

A common method for studying infant cognition is showing a baby a normal object that acts in an unexpected, or “magical,” way, such as a ball hovering in midair or passing through a wall. A team of researchers noted that some babies stare at the magical objects a long time, while others just glance at them and look away.

Researchers weren’t sure whether the variability was due to babies getting distracted or hungry, or whether it indicated particular babies reacting to the world with differing levels of curiosity. 

They decided to track the reactions of 65 babies to magical objects over time. They found that the babies who looked at the magical objects a long time at 11 months of age were the same babies who stared at them a long time at 17 months, while the same babies who were uninterested at 11 months largely remained uninterested at 17 months. At age three, the babies who had reacted with the most curiosity were the ones most likely to be rated by their parents as information-seeking and problem-solving.

Scientists still want to find out how long this pattern continues, and what outcomes early curiosity has on the children’s futures. The kids are probably curious as well.

Most of us are probably familiar with the image of salmon jumping upstream or over obstacles in the water. But why is it so common to see them leaping out of still water too?

Maybe they're just showing off. Or, they might be trying to shake off sea lice.

Scientists noticed that young sockeye salmon jump out of the water and skim its surface with their tails an average of nine times a day, and it’s clear they’re not just leaping over obstacles. Researchers had a hunch the salmon were trying to get rid of sea lice, since it’s known that fish with sea lice jump out of the water fourteen times more often than fish that are sea lice-free.

A sea louse is a parasite about the size of a pea that feeds on mucus, blood, and skin, so it makes sense why salmon want to get rid of them. But does jumping actually do the trick?

That’s what scientists wanted to find out. They caught salmon infested with sea lice and divided them into two groups. They put one into an ocean pen where they could leap out of the water, and another into a pen with netting covering the water’s surface. After three days, the salmon that couldn’t jump out of the water had twenty-eight percent more sea lice than the ones that could.

So the salmon figured out something that works, eventually. It takes the fish an average of fifty-six jumps to dislodge a single sea louse.

Not the best stats. They should really work on their technique.

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• Science Magazine - Why are these salmon jumping?

Could the moon ever cause a person to tan? It's not that strange of a question: after all, moonlight is reflected sunlight. And following that logic-train, if direct sunlight can cause people to tan--and even burn--then why not reflected sunlight?

The actual answer is no. People can't get a tan from the moon, no matter how bright. Tanning is a reaction to the sun's ultraviolet light. Skin produces melanin as a result of continued sun exposure. The amount of melanin produced does vary based upon individual's genetic factors (such as darker skin tones, as well as other traits).

Ultraviolet rays are harmful; they can cause skin damage and even cancer. Skin produces melanin as a defense against ultraviolet rays. Melanin absorbs ultraviolet radiation, thereby protecting the skin's cells. So the more ultraviolet light, the more at risk skin is.

Why the moonlight doesn't make people tan is because sunlight reaching Earth via the moon just doesn't have enough ultraviolet oomph to trigger the skin's defensive shield.

Even though a full moon may look really bright, the surface of the moon is actually pretty dark. The moon absorbs most of the sunlight that hits it.

Of course, some of the sun's reflected ultraviolet light does reach us. Theoretically, prolonged exposure to moonlight could cause some damage.

In this case "prolonged" means hundreds of years of continuous moon bathing. Under normal conditions our skin quickly repairs whatever minimal damage is caused by the light of the silvery moon.

There’s rarely just one fruit fly hovering over the browning bananas in your fruit bowl. That’s because fruit flies are social creatures, spending most of their time together in groups.  

Scientists have noted that other social animals, including humans, tend to eat more and sleep less when isolated. To help understand these observations, a group of scientists decided to study fruit flies to find out what’s going on in their brains when they’re socially isolated.

They found that putting fruit flies in smaller groups didn’t change their behavior; even flies isolated in groups of two acted the way they usually do. But once a fruit fly was isolated all by itself, it began to show the behaviors that scientists have observed in other animals—eating more and sleeping less.

When they took their investigation further, they found that these changes were connected with brain cells called P2 neurons. When the team shut off P2 neurons in flies that had been isolated, the flies stopped overeating and returned to their normal sleeping habits. When they boosted the neurons’ functioning in flies that had only been isolated for a day, the flies’ eating and sleeping habits were the same as those of flies that had been isolated for a whole week. The scientists think that these neurons are linked to the fruit flies’ perceptions of how long they’ve been isolated.

We don’t know whether these same biological mechanisms are linked to similar behaviors we’ve seen in humans. But if you’ve been noticing your eating and sleeping habits change during isolation too, maybe you’ll feel some kinship with those pesky fruit flies.

Reviewer: Jini Naidoo, the University of Pennsylvania

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ScienceDaily - Lonely flies, like many humans, eat more and sleep less