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Bull sharks are among the most dangerous sharks in the world, according to many experts. This is because they’re an aggressive species of shark, and they tend to hunt in waters where people often swim: along tropical shorelines. Bull sharks live throughout the world, in shallow, warm ocean waters. They’ve been known to swim up into freshwater rivers. Humans are not part of a bull shark’s normal prey. Bull sharks will eat almost anything, but their diet consists mainly of fish. They also sometimes eat dolphins and sea turtles. Bull sharks even eat other sharks. They hunt during the day and at night. Sharks must keep salt in their bodies to survive, and most can live only in salt water. But bull sharks have developed special adaptations—the way their kidneys function and special glands near their tails—that help them keep salt in their bodies even when they’re in freshwater. Scientists are still studying these sharks to figure out why they developed this unusual ability.
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If you live in the contiguous United States, you’ve almost certainly seen (or heard!) an American crow. Crows range from southern Canada throughout the United States. As an adult, this bird is entirely black from bill to tail, except for its brown eyes. Adult crow feathers have a glossy sheen. These noisy birds are often recognizable by their distinctive, loud cry, called a caw. They are often mistaken for the common raven, but ravens are larger, have differently shaped bills, pointed wings and tails, and hoarser cries. American crows often live in family groups. Both members of a breeding pair help build the nests, and the female crow usually lays four or five eggs in the spring or summer. After about five weeks in the nest, the young birds begin learning how to fly and catch prey. Crows sometimes stay near the place where they were born to help raise other young crows. Crows gather in large groups during the winter. They congregate late in the day in areas with large trees. This behavior is known as winter roosting. Crows will eat almost anything, from insects and small animals such as frogs to fruit and nuts. They prefer open areas with access to trees and can sometimes be found around vegetable gardens. Crows also frequently live in suburban neighborhoods and in parks. Crows are considered to be very intelligent birds. Text by Sara Zeglin / NGS Staff
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Chipmunks are part of the squirrel family, and while they look similar to their bushy-tailed cousins, chipmunks are actually smaller, with alternating light and dark stripes along their cheeks and backs. There are 25 species of chipmunk, 24 of which live in North America. Chipmunks are excellent tree climbers and swimmers who live in a variety of habitats, including plains, mountains, forests, and deserts. Chipmunks like to live alone in holes or burrows called dens. Chipmunks hibernate in cold weather, which means they spend most of the winter sleeping in their dens. One chipmunk can gather up to 165 acorns in a day. In just two days, a chipmunk can collect enough food to last an entire winter, although chipmunks typically hoard much more food than necessary. Chipmunk young are born in late spring, and stay in the nest for up to six weeks. Female chipmunks have one or two litters per year, each with four or five babies. Chipmunks are 7.2 to 8.5 inches (18.5 to 21.6 centimeters) long including their tails, which can account for nearly half of their length.
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Although native to Europe, earthworms are found throughout North America and western Asia. They do not live in deserts or regions where there is permafrost or permanent snow and ice. Typically only a few inches (7 or 8 centimeters) long, some members of this species have been known to grow to a snakelike 14 inches (35 centimeters). Earthworms‘ bodies are made up of ringlike segments called annuli. These segments are covered in setae, or small bristles, which the worm uses to move and burrow. These terrestrial worms typically dwell in soil and moist leaf litter. Their bodies are characterized by a „tube within a tube“ construction, with an outer muscular body wall surrounding a digestive tract that begins with the mouth in the first segment. As they burrow, they consume soil, extracting nutrients from decomposing organic matter like leaves and roots. Earthworms are vital to soil health and to plants growing in it because they transport nutrients and minerals from below to the surface via their waste. An earthworm can eat up to a third of its body weight in a day.
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Tarantulas give people the creeps because they have large, hairy bodies and legs. While these large spiders can take a painful bite out of a human, a tarantula’s venom has a low toxicity to people. Tarantulas move slowly on their eight hairy legs, but they are accomplished nocturnal predators. Insects are their main prey, but they also target bigger game, including frogs, toads, and mice. Tarantulas are burrowers and typically live in the ground. There are hundreds of tarantula species found in most of the world’s tropical, subtropical, and desert regions. They vary in color and behavior according to their specific environments. A tarantula doesn’t use a web to trap its prey, though it may spin a trip wire to signal an alert when something approaches its burrow. These spiders grab with their legs, inject paralyzing venom, and then bite their prey with their fangs. They also secrete digestive enzymes to liquefy their victims‘ bodies so that they can suck them up through their strawlike mouth openings. Yum! Tarantulas have few natural enemies, except for the parasitic pepsis wasp, which can paralyze a tarantula with its sting and lay its eggs on the spider’s body. When the wasp eggs hatch, the larvae chow down on the still living tarantula. Tarantulas shed their external skeletons in a process called molting. During the process, they also replace internal organs, such as stomach lining, and can even regrow lost legs.
even regrow lost legs. 4:25 A Biting Tarantula and Venomous Death Adder Jack finds

Giraffes grow about 4 feet (1.2 meters) in their first year of life. A newborn giraffe is about 6 feet (1.9 meters) tall at birth and weighs about 150 pounds (68 kilograms). Many young giraffes, called calves, die from lion attacks during their first year of life. Once a giraffe reaches adulthood its height is often enough to protect it from lions. Adult giraffes, however, must still be careful of lions when they are bending down to drink water or rest. Usually giraffes will drink or rest in shifts so that at least one giraffe is always on the lookout for approaching predators. The giraffes‘ height and excellent vision give them a wide view of the grasslands where they live, making it easy to spot predators from a distance. Some scientists believe that other animals—such as zebras, antelope, and wildebeests—often congregate near giraffes to take advantage of their ability to see danger from a distance. The giraffe could be considered the early warning system of the African grasslands.
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Snowy white tundra swans breed in the Arctic. Young swans have fluffy gray feathers in their first winter. The tundra swan call is higher and more like that of a Canada goose. Tundra swans mate for life and pair up for nearly a year before breeding. They breed in solitary pairs spread out across the Arctic tundra. They can be nasty protectors and are able to fend off predators like foxes. They prefer to nest near wetlands containing pondweed. They line their large, stick nests with moss and grasses. Females lay about four eggs and incubate them for 32 days. These large birds feed by dipping their heads underwater to pluck aquatic plants, roots, and tubers. Their diet consists of mainly submerged plants and roots, but they will also eat some cereal grains, corn, and mollusks, which are a kind of shellfish. The majestic tundra swan is a strong swimmer and can take off from the water with a running start and beat their wings until airborne. Their flapping wings produce a sound that earned them the name „whistling swan.“ They migrate thousands of miles to enjoy a milder winter in North America’s Atlantic and Pacific coastlines, bays, and lakes. Twice a year, they fly 3,725 miles (6,000 kilometers) round-trip between the breeding and wintering locations.
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Rattlesnakes live in many places and habitats in the Western Hemisphere, from mountains to deserts and plains. There are more than 24 rattlesnake species and all of them have that most-famous feature: the rattle! The rattle is found at the tip of the rattlesnake’s tail. The snake uses the rattle to warn potential aggressors to back off or to distract prey. The famous rattle noise comes from the sound created when hollow and bony doughnutlike segments in the rattle bang together. As rattlesnakes age, segments on the end of the rattle wear out and break off. New segments grow when the rattlesnake sheds its skin, or molts. Like other snakes, rattlesnakes don’t have ears and can’t hear most sounds. They detect movement by sensing vibrations in the ground. Their eyes see well even in low light. The rattlesnake’s triangular head contains a hollow spot between the eyes and nostrils called a pit. This pit is actually a sensory organ that helps the rattlesnake hunt in darkness by detecting body heat.
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Space explorers go above and beyond on the job. Here are five cool things about these pioneers.
You won’t find baths or showers in space.

Scorpions are arachnids and have eight legs like their cousins—spiders, mites, and ticks. They can quickly grab an insect with their pincers and whip their telson, the poisonous tip of their tail forward and sting their prey. They use their poison to kill prey and to defend against predators. Scorpions look like small lobsters and may be the first animals to move from water to land hundreds of millions of years ago. They have been around since before the age of the dinosaurs. Fossils of scorpions from Scotland hundreds of millions of years ago show that their appearance hasn’t changed over the millennia, but they are now half the size of their ancient ancestors. Only 30 or 40 species around the world have strong enough poison to kill a person. Each species has a special type of venom that works well against a chosen prey. Scorpions typically eat insects, but when food is scarce, they can slow their metabolism to as little as one-third the typical rate for arthropods. This technique enables some species to use little oxygen and live on only one insect per year. Such survival skills allow scorpions to live in some of the planet’s toughest environments. Researchers have even frozen scorpions overnight, only to put them in the sun the next day and watch them thaw out and walk away. However, they are burrowing animals, so in areas of permafrost or heavy grasses, where loose soil is not available, scorpions may not be able to survive.
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