Category: Prey-predators

The Fish that Sees Red

5/19/2022

Steve Jenkins

Making Sense of the Natural World

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/
The-Fish-that-Sees-Red.

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World Penguin Day

4/25/2022

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Jim Whiting
The Running Encyclopedia

Who doesn’t like penguins? Their waddling gait is fun to watch. They have little fear of humans so it’s easy to get next to them. Penguin movies such as Happy Feet and The Penguins of Madagascar are box office hits.

World Penguin Day on April 25 focuses attention on these loveable flightless fowl. Some people dress up in black and white clothing. Many read books about penguins or watch penguin movies.

I was fortunate to get up close and personal to thousands of penguins during a trip to Antarctica. As our ship neared the tip of the Antarctic Peninsula—the closest point to the southern tip of South America which had been our departure point—we marveled at how effortlessly they skimmed through the water beside us. Soon we marveled at another characteristic. We were at least two or three miles offshore when the harsh odor of the poop generated by all those penguins wafted over the ship.

We relished the opportunity to go ashore and wander through their rookeries. There were lots of juveniles, covered with gray fuzz that would eventually fall off and be replaced by their characteristic black and white plumage. None of them seemed to mind our presence.

But we had several harsh reminders that we weren’t in a zoo. Several century-old stone huts provided shelter for explorers who slaughtered hundreds of penguins to eat during the long, harsh Antarctic winters. Skuas, nasty predatory birds, routinely feed on penguin chicks. We saw the discarded remains of several skua meals. Danger can also come from the depths. A couple of times we observed large seals relaxing on ice floes with bright red stains next to them.

The saddest sight came one afternoon when we took a Zodiac inflatable boat to shore. A penguin stood forlornly on top of a small ice floe, a leopard seal thrashing the water next to it. We asked our guide if we could rescue the doomed bird. He shook his head. “The water is too rough,” he said. “Too much chance of falling in if anyone tried to step out onto the floe. And you don’t want to be anywhere near an angry half-ton leopard seal that feels his dinner is being taken away from him.”

On our way back to the ship, there was no sign of the lone penguin. We had to accept that we couldn’t interfere in the natural course of things.

Although all penguin species are native to the Southern Hemisphere, they are not found only in cold climates, such as Antarctica. In fact, only a few species of penguin live so far south.

An Adélie penguin feeding its young

Greenpeace invites you to celebrate World Penguin Day and also to join the campaign towards its protection. You can learn more by visiting this website: ttp://act.gp/wpd2013.

All images ©Jen Goode

Jim Whiting has written more than 100 titles and edited another 150 or so, with subjects ranging from authors to zoologists and including classical musicians and contemporary pop icons, saints and scientists, emperors and explorers. Many of his books have received glowing reviews.
He's also ventured into a number of classrooms and served as a presenter at writers' conferences, conveying the enthusiasm for writing and for a good story that still animates him. Check out his work here.

MLA 8 Citation
Whiting, Jim. "World Penguin Day." Nonfiction Minute, iNK Think Tank, 25 Apr.
2018, www.nonfictionminute.org/the-nonfiction-minute/World-Penguin-Day.

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The Way Polar Bears Stay Warm is Cool

1/7/2022

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Vicki Cobb

The Master Chef of Kids' Hands-on Science

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!

The polar bear is the largest land carnivore. Its long non-retractable claws help it get a grip on the icy surface it prowls for prey. Wikimedia Commons

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.

The polar bears’ white appearance serves as ideal camouflage in a snow-covered environment. Art by Barbara Lavelle from This Place is Cold by Vicki Cobb.

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.

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How Skunks Play Fair

12/15/2021

1 Comment

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 was 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.

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Meet Earth's Incredible Gliders

4/29/2021

2 Comments

Sneed B. Collard III

Connecting Scientists and Kids

Have you ever seen a lizard hurtling over your head? How about a frog sailing down from the tree tops? I’m not making these animals up. They belong to one of earth’s most astonishing groups of animals.

            Gliders.

            Gliders travel through the air, but they don’t fly. Instead, they glide. What’s the difference? Well, to get itself off the ground, a bird, bat, or insect has to generate a force called lift. A flying animal generates lift using its wings, which are attached to powerful flight muscles. These wings move and bend in complicated motions to counteract the force of gravity.

            Gliding animals do not have muscle-powered wings. Instead, most gliding animals have special flaps or folds of skin called patagia. Like wings, the patagia generate lift—but only after the animal is already moving through the air.

            When chased by a snake, a Draco lizard leaps from its tree. Instead of plunging to its death, it spreads out its rib cage into two elegant airfoils covered with skin. As air rushes over them, these airfoils—the patagia—generate lift to keep the lizard from falling straight down. The lizard does steadily descend toward earth, but it is also riding the air. It can change directions, pull a U-turn, and control where it wants to go. In the process it can travel hundreds of feet before landing on another tree or on the ground.

            The patagia of Wallace’s frogs lie between their toes. These frogs usually live up in the trees, but when it is time to mate or lay eggs, they leap, spread out their toes, and glide to earth.

            Earth’s most astonishing gliders may be five species of gliding snakes. These snakes don’t have patagia. Instead, they flatten out their bodies and “crawl” through the air. Scientists aren’t sure if the crawling motion helps generate lift, or if lift comes mainly from a snake’s flattened shape, but the animals can glide more than 100 feet before landing.

            Most of earth’s gliding animals live in Southeast Asian rainforests, which are home to more than eighty species of gliding lizards, frogs, snakes, and mammals. In North America, we have only two gliding animals: Northern and Southern flying squirrels. Despite their name, flying squirrels don’t fly. They glide—and are adorably cute! Want to see one? Try shining a flashlight on a bird feeder at night!

A male Draco lizard extending his gular flag (throat flap) and patagi (wings). While not capable of powered flight Dracos often obtain lift in the course of their gliding flights. Glides as long as 200 feet have been recorded, Wikimedia

Wallace's frogs live almost exclusively in the trees, and leap and "fly" from tree to tree or to bushes. The membranes between their toes and loose skin flaps on their sides catch the air as they fall, helping them to glide, sometimes 50 feet or more, to a neighboring tree branch or even all the way to the ground. They also have oversized toe pads to help them land softly and stick to tree trunks. Wikimedia

Flying squirrels are able to glide from one tree to another with the aid of a patagium, a furry, parachute-like membrane that stretches from wrist to ankle. Their long tail provides stability in flight. Wikimedia

There are five recognized species of flying snake, found from western India to the Indonesian archipelago. They flatten out their bodies and parachute or glide using their ribs to become flat, and then they whip their bodies in a fast, rhythmic S-shape to stay airborne. Wikimedia

Illustrated with arresting photographs, Sneed B. Collard's Catching Air: Taking the Leap with Gliding Animals takes us around the world to learn why so many gliders live in Southeast Asia, and to find out why this gravity-defying ability has evolved in Draco lizards, snakes, and frogs as well as mammals. Why do gliders stop short of flying, how did bats make that final leap, and how did Homo sapiens bypass evolution to glide via wingsuits and hang gliders―or is that evolution in another guise?

MLA 8 Citation
Collard, Sneed B., III. "Meet Earth's Incredible Gliders." Nonfiction Minute,
iNK Think Tank, 11 Apr. 2018, www.nonfictionminute.org/
the-nonfiction-minute/meet-earths-incredible-gliders.

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The Fish that Sees Red

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How Skunks Play Fair

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