Polar bears are built to withstand some of the coldest temperatures on the planet. Their brown and black bear cousins avoid the winter cold by digging dens and sleeping. But, except for pregnant females, polar bears spend the arctic winter outside where temperatures could be -40° F (which equals-40 °C) and windy. That’s too cold for humans. You could go outside, but only for only a few minutes with every part of your body completely covered. And if you didn’t wear goggles, your eyelashes would freeze and break off if you touched them.
Polar bears are warm-blooded like us with a body temperature of about 98°F/37°C. But they are invisible to night-vision goggles that pick up the infrared rays that warm-blooded creatures, including humans, give off. Why? Nature has given polar bears enough insulation to prevent body heat from escaping. They are toasty warm and comfortable in the frigid arctic.
Their heat insulation is in several layers. Under their skin, there is a 4-inch (21.5 cm) layer of fat. Next to the skin is a dense layer of woolly fur that also keeps heat in. The fur you see is a thick layer of long, colorless guard hairs that shed water quickly after a swim. They are stiff and transparent and hollow. In the arctic sunlight, the hairs act like mirrors and reflect white light, which acts as camouflage against the snow so the bears are not seen by their prey. Polar bear skin is actually black, so that it can absorb the invisible warm infrared rays of the sun and the bear’s own body heat, both of which are reflected back by the guard hairs.
Most warm-blooded animals raise their body temperatures through exercise. Polar bears hunt seals, which they don’t often chase. They prefer to sit at the edge of an ice floe and wait for dinner to arrive. At best, they’ll lumber after a seal at four and a half miles (7.25 km) an hour, raising their body heat to 100°F (38°C). When that happens, they go for a swim to cool off.
Cold won’t kill off the polar bears, but global warming can. As polar ice disappears, so does the hunting ground for seals. Not so cool!
Close up, the polar bear guard hairs are transparent. This allows the infra-red light (heat) from the sun to pass through them to be absorbed by the black skin under the hairs. The hairs also act like mirrors , reflecting back to the skin any infra-red radiation escaping from the bears body so it can be reabsorbed. Thus, the insulation is just about perfect with no infra-red radiation escaping. The hairs are also coated with oil so they drain quickly after a swim.
Vicki Cobb's This Place Is Cold shows how the latitude of Alaska affects the lives of the plants, animals and people who live there. It is gloriously illustrated by Barbara Lavallee, a long-time Alaskan resident and artist.
Vicki is a member of Authors on Call—she can visit your classroom with interactive videoconferencing: Read more about her here.
MLA 8 Citation
Cobb, Vicki. "The Way Polar Bears Keep Warm Is Cool." Nonfiction Minute, iNK Think Tank, 29 Nov. 2017, www.nonfictionminute.org/The-Way-Polar-Bears-Keep-Warm-Is-Cool.
Earth’s temperatures are getting warmer. In fact, sixteen of the seventeen hottest years on record have occurred since the year 2000. These warmer temperatures are driving larger, long-term changes in our planet’s weather and climate. Scientists refer to these changes as “climate change.”
In a few places, climate change might be welcome, but around the world, warmer temperatures and other changes are leading to a host of problems from rising sea levels to more extreme weather events and the spread of harmful human diseases.
Professor Scott Mills, from the University of Montana, wanted to see how climate change might be affecting one particular animal called the snowshoe hare.
Snowshoe hares live in regions of North America that receive snow every winter. The hares, in fact, change their coat color from brown to white and back again every year. This helps camouflage them against their background—and hides them from the eyes of lynx, owls, and other hungry predators.
Here’s the thing: snowshoe hares can’t choose when they molt, or change their coat color. Molt timing is controlled by their genes, which are part of the DNA inside their bodies. If a hare’s genes make it molt to white in October, but snow doesn’t fall until December, the hare will stick out like a light bulb against the brown earth. And that’s a problem. Why? Because almost everywhere on earth, the length of time with snow on the ground is growing shorter and shorter.
To find out if shorter winters might harm hare populations, Scott and his team spent three years tagging and following hares. They measured how many were born, how many died, and what they died from. They also recorded whether the hares were matched or mismatched against their backgrounds.
They discovered that predators killed mismatched hares significantly more often than hares whose coats match their backgrounds. Scott and his team also calculated that over the next one hundred years, this greater mortality, or death rate, could lead to the decline or disappearance of many snowshoe hare populations.
The good news? Different hares molt at different times. This may help some hare populations adapt to shorter winters and longer periods without snow.
Hares are not the only animals affected by shorter winters. More than twenty species of animals including lemmings, weasels, hamsters, and Arctic foxes change their coat colors every year. Scott’s research helps us predict what might happen to these animals—and decide what we can do to protect them.
Scott’s discoveries about Montana snowshoe hares, together with experts’ predictions about our future climate, indicate that hares will be mismatched between 5-½ and 10 weeks by the end of this century.
Before tagging and putting a radio collar on a snowshoe hare, Professor Mills and his team must weigh and measure it.
This snowshoe hare has been tagged and fitted with a radio collar—and is now ready to help scientists learn more about snowshoe hare survival.
Even from a great distance, a mismatched hare stands out like a glowing light bulb. (Photo Courtesy of L. Scott Mills research laboratory)
Besides serving as popular prey for predators, snowshoe hares are irresistibly cute. This is a young hare, also called a leveret.
Sneed B. Collard III is the author of more than eighty award-winning books, many focusing on science and the natural world. His entertaining memoir Snakes, Alligators, and Broken Hearts—Journeys of a Biologist’s Son recounts his challenges and adventures growing up as the son of divorced biologist parents, and the experiences that would one day lay the foundation for his writing career. He is a dynamic speaker and offers school and conference programs that combine science, nature, and literacy. To learn more about him and his talks, visit his website, www.sneedbcollardiii.com.
This book was reviewed by Vicki Cobb in the Huffington Post: "The Cheeseburger of the Forest".
MLA 8 Citation
Collard, Sneed B., III. "Hopping Ahead of Climate Change." Nonfiction Minute, iNK Think Tank, 15 Nov. 2017, www.nonfictionminute.org/hopping-ahead-of-climate-change.
Are skunks aggressive, dangerous animals? Or are they peaceful animals that try to avoid trouble? Well, biologists who study skunks think of them this way: if life were a sport, skunks would be known for their strong defense and for playing fair.
Skunk stinkiness comes from a chemical weapon called musk. Foxes, weasels, and some other mammals also produce musk, but skunk musk is especially strong and long-lasting. And only skunks use musk to defend themselves from attack.
Picture a skunk ambling along in the night, looking for food. It digs in the soil to get tasty earthworms and beetle grubs. The black and white fur that comes with just being a skunk sends a warning. This color pattern is unusual among mammals. It signals: "Beware, don't mess with me!"
Suppose a coyote or other predator ignores this first warning. It steps toward the skunk. When a skunk feels threatened, it faces the danger. It raises its tail and tries to look as big as possible. It stamps its feet and clicks its teeth together. It may growl or hiss.
Oh, oh! Despite all of these warnings, the coyote growls and comes closer. Now the skunk gets really serious. It twists its body into a U-shape, so it can see the coyote and also aim its rear end toward it. The skunk's tail arches over its back, away from its rear—the final warning. This gives the skunk a clear shot, and also protects its own fur from the stinky musk. Skunks try to avoid smelling bad!
From two grape-sized glands, a skunk can spray musk as a fine mist, or squirt a stream. It can squirt accurately for about 12 feet (3.7m), and hit an attacking animal right in the face. The musk stings the predator's eyes, and can blur its vision for a while. And it stinks! Animals hit with this musk learn to never bother a skunk again.
A skunk's glands store enough musk to fire a half dozen shots but then need a week or so to produce more. This is seldom a problem, since a skunk sprays only when its life seems to be in danger. Some skunks can go for months or even years without spraying musk. That's fine with them. Skunks want to avoid trouble, and "play fair" with their many warnings.
A skunks’s stripes point to where the spray comes out. A 2011 study found that animal species that choose fight over flight when faced with a predator often have markings that draw attention to their best weapon. So while a badger has stripes on his face to highlight his sharp teeth, skunks’ stripes are perfectly positioned to highlight their ability to spray potential threats. By http://www.birdphotos.com via Wikimedia Commons
Skunks are so nice that some people want to keep them as pets. The striped skunk is the most social skunk and the one most commonly domesticated. The legality of keeping skunks as pets in the US varies by state, with it being illegal in a majority of them. By Matt MacGillivray via Wikimedia Commons
Larry Pringle has written many animal books, among them The Secret Life of the Red Fox. His The Secret Life of the Skunk will be published by Boyds Mills Press in 2019. It is about spring and summer in the lives of a mother striped skunk and her kits.
ML 8 Citation
Pringle, Laurence. "How Skunks Play Fair." Nonfiction Minute, iNK Think Tank, 8 Nov. 2017, www.nonfictionminute.org/how-skinks-play-fair.
celebrating nature, inspiring good writing
This summer, you may be able to observe an amazing event in nature. You can watch a small animal build a structure much bigger than itself, using materials from inside its own body!
This is what happens when a spider spins a web. Inside a spider are glands that can produce seven different kinds of silk. The silk comes out of little spigots, called spinnerets, at the rear of the spider's body.
A strand of spider silk is stronger than a similar strand of steel, and spiders use this amazing material in many ways. If they catch an insect, they may wrap it in silk, to eat later. Female spiders enclose their eggs in a silken sac to protect them. And some spiders—almost always females—make webs that are death traps for insects.
Webs can be in the shape of funnels, sheets, or domes, but the best-known are called orb webs. From an orb web's center, lines of silk radiate out in all directions, like the spokes of a bicycle wheel. After building this basic structure, a spider goes round and round, laying down ever-bigger circles of silk. Some of the silk threads have sticky glue to catch a moth or other prey. A spider can create this whole complex design in an hour or less.
When an orb web is complete, some kinds of spiders wait right in the center. Others hide at an edge. Either way, the builder keeps a front leg in touch with the web. Vibrations from the threads tell a spider whether prey has been caught.
Spiders often have to repair their webs, and some species routinely build a new one every day. And they recycle! They eat most of their old web. After digestion, it becomes brand new silk for the next construction job.
You may be able to watch a spider on the job. Look for webs in a field, park, or backyard. Also look for webs near doors, windows, or on a porch. The nighttime lights from such places attract night-flying insects, and spiders often build webs there. They may or may not be orb webs, but watching any kind of spider at work on its silken insect-trap can be fascinating fun.
And remember: the spider wants nothing to do with you. It is just trying to stay safe and catch some food.
This video was shot by Ingrid Taylor, " I shot this a few minutes after the rain subsided, when the City of Spiders outside the door came to life. Mass web-building and repair going on..." wikimedia commons
.To learn more about the lives of spiders, and see spectacular realistic illustrations, see Laurence Pringle's book:
MLA 8 Citation
Pringle, Laurence. "Watch a Webmaster at Work!" Nonfiction Minute, iNK Think
Tank, 14 June 2018, www.nonfictionminute.org/the-nonfiction-minute/
Have you ever noticed how photographs of underwater scenes have a bluish tint? Sunlight is made up of a rainbow of colors, but when it enters the water the reds and yellows in the light are quickly filtered out. The blues and greens penetrate deeper into the water and give those watery scenes their peculiar cast. Because there is very little red light in the deep sea, most of the animals that live there have never evolved the ability to see the color red. This is why many deep-sea animals are red. In the depths of the ocean, a creature that can’t be seen is safe from many predators.
There is an unusual fish that takes advantage of its fellow sea creatures’ colorblindness. The stoplight loosejaw, a member of the dragonfish family, can see the color red. Not only that, but it has a patch on its face that glows red. It also has a glowing green spot on its face, which is probably used to communicate with other dragonfish. These red and green patches explain the “stoplight” part of this fish’s name. The “loosejaw” comes from this fish’s ability to open its mouth extra wide and swallow large prey. Scientists think that the open structure of the lower jaw allows the fish to close its mouth quickly, making it difficult for prey to escape. Relative to its size, the stoplight loosejaw has one of the widest gapes of any fish, with a lower jaw measuring one-quarter of the fish’s length. It’s not easy for animals that live in the dark waters of the deep sea to find prey. Many of them, including the stoplight loosejaw, have large mouths and sharp fangs that help ensure that their prey cannot escape.
Below about 650 feet (200 meters), very little sunlight penetrates the ocean. Below 3,300 feet (1,000 meters), the only light is that produced by living creatures. Almost all deep-sea creatures can bioluminescence, or make their own light. But the light they produce is usually blue or green. When the stoplight loosejaw switches on its red spotlight, other creatures in the water are illuminated. Being blind to the color red, they don’t realize that they’ve been spotted. Dragonfish are not known as picky eaters. If one of the lit-up animals is a fish, shrimp, or other suitable prey, the stoplight loosejaw quickly grabs it and swallows it.
The stoplight loosejaw's attributes include a red spot, hinged jaws, and needle-like teeth. Illustration by Steve Jenkins
There are two kinds of stoplight loosejaws. The Northern (Malacosteus niger) shown here and the Southern. Together they are found everywhere in the world except the North and South Poles. Wikimedia Commons
Steve Jenkins has written and illustrated more than forty
nonfiction picture books, including the Caldecott Honor–
winning What Do You Do with a Tail Like This? and the
Boston Globe Horn Book honor–winning The Animal Book.
His most recent books are Apex Predators: Top Killers Past
and Present and Who Am I?, an animal guessing game
written with Robin Page.
MLA 8 Citation
Jenkins, Steve. "The Fish That Sees Red." Nonfiction Minute, iNK Think Tank, 6
June 2018, www.nonfictionminute.org/the-nonfiction-minute/
For Vicki Cobb's BLOG (nonfiction book reviews, info on education, more), click here: Vicki's Blog
The NCSS-CBC Notable Social Studies Committee is pleased to inform you
that 30 People Who Changed the World has been selected for Notable Social Studies Trade Books for Young People 2018, a cooperative project of the National Council for the Social Studies (NCSS) & the Children’s Book Council