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Bull sharks are 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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Reaching up to 13 feet (4 meters) long and weighing as many as 1,300 pounds (600 kilograms), West Indian manatees look more like small cars than people. Despite their large size, manatees are graceful swimmers. Although they usually move along in slow motion, they can also cruise, or swim at a steady pace, at five miles (eight kilometers) an hour. In short bursts they can even top 15 miles (24 kilometers) an hour! While cruising, manatees push themselves forward by moving their strong tails up and down. They steer with the help of their flexible flippers. When in shallow water, manatees use their flippers to walk, slowly placing one in front of the other. Like whales and dolphins, manatees are mammals. Although they live in water, they have to surface frequently to breathe air. While swimming, manatees take in air every three or four minutes. When they are resting, they can stay underwater for up to 15 minutes. Manatees are gentle animals. They rarely fight, and they have no natural enemies. Subsisting on water plants and plants that grow at the water’s edge, a manatee takes in up to 1 pound (0.5 kilogram) of food for every 10 pounds (5 kilograms) it weighs.
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Kangaroos possess powerful hind legs, a long, strong tail, and small front legs. Kangaroos belong to the animal family Macropus, literally „big foot.“ Thanks to their large feet, kangaroos can leap some 30 feet (9 meters) in a single bound, and travel more than 30 miles (48 kilometers) per hour. Kangaroos use their strong tails for balance while jumping. They are the tallest of all marsupials, standing over 6 feet (2 meters) tall. Kangaroos live in Eastern Australia. They live in small groups called troops or herds (“mobs” by Australians), typically made up of 50 or more animals. If threatened, kangaroos pound the ground with their strong feet in warning. Fighting kangaroos kick opponents, and sometimes bite. Female kangaroos sport a pouch on their belly, made by a fold in the skin, to cradle baby kangaroos called joeys. Newborn joeys are just one inch long (2.5 centimeters) at birth, or about the size of a grape. After birth, joeys travel, unassisted, through their mom’s thick fur to the comfort and safety of the pouch. A newborn joey can’t suckle or swallow, so the kangaroo mom uses her muscles to pump milk down its throat. At around 4 months, the joey emerges from the pouch for short trips and to graze on grass and small shrubs. At 10 months, the joey is mature enough to leave the pouch for good. Besides humans and wild dogs called dingoes, kangaroos face few natural predators. Heat, drought, and hunger due to vanishing habitat are the biggest dangers kangaroos face.
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If you were to check in one morning on a group of ring-tailed lemurs, you’d likely see them sitting on the ground, facing the sun with their arms outspread. Ring-tailed lemurs often spend hours soaking up the warmth of the sun. And they do it in a group, since they’re social animals. In a troop, or group, of ring-tailed lemurs, which typically numbers between 15 and 20 individuals, females rule. If a squabble breaks out between a male and a female, the female lemur always wins the argument. Lemur troops establish territories, which they defend against other troops. The male lemurs tend to hang back during battles. Male ring-tailed lemurs come and go from one troop to another, while females stay with the one in which they were born. As the troop moves from feeding site to feeding site, the core group of females settles into the best feeding spot (generally a good tree) and eats first. The males wait for them to finish or feed in a less desired tree nearby. The same goes for often hard-to-find water which collects in tree hollows. Some female lemurs are dominant over the other females and higher-ranking males strut around with their heads and tails held high, while the lower-ranked lemurs keep their tails and heads down.
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Hedgehogs have prickly spines everywhere except on their face, legs, and bellies. By curling into a tight ball and tucking in their heads, tail, and legs, they protect the parts of their bodies that do not have stiff, sharp spines. Often compared to pincushions, hedgehogs depend on their spines for defense—both while they sleep and when they face enemies. The head and body of adult hedgehogs range from 5 to 12 inches (13 to 30 centimeters) long and their tail can add 1 to 2 inches (3-5 centimeters). When hedgehogs are born—up to seven in a litter—their spines are soft and short. Soon after birth, their spines harden, becoming stiffer, sharper, and longer. Babies stay in the nest until they’re about three weeks old. By that time, their eyes are open, their spines are effective, and they can safely follow their mother outside the nest as she looks for food. Top on the hedgehog’s menu are insects, followed by small mice, snails, lizards, frogs, eggs, and even snakes. Hedgehogs sometimes add extra protection to their spines by „self-anointing.“ Immune to poisons in some plants, hedgehogs sometimes eat those plants and then make a frothy saliva in their mouths. The hedgehogs then lick their spines, spreading the saliva with the plant’s poison all over the spikes. Though hedgehogs mainly stay on the ground, they swim quite well and even climb trees.
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White-handed gibbons are small tailless apes with soft, thick fur. They live in trees and like to stay high up in the canopy of trees. Their very long arms allow them to swing effortlessly among the tree branches. They can also change direction in a split second, and can catch birds in midair and eat them after landing. Gibbons are among the fastest of all primates. They are so fast that they barely touch a branch before swinging off and grabbing the next branch, and they „fly“ up 40 feet through the air and leap long distances before landing. They can cross rivers or large openings in the forest with this acrobatic technique. Gibbons sometimes have accidental falls if a branch breaks and they do suffer from bone fractures in the wild. They sleep sitting up in trees with bent knees and faces buried between the knees and chest. Gibbons are bipedal and walk across tree limbs on two feet. They hold their arms high in the air for balance when they walk or run along the ground or on branches. White-handed gibbons have white fur on the upper sides of their hands and feet. They live in small family groups made up of a male and female pair and their young. They sing duets, with the male and female complementing each other’s part. These duets help the couple bond and mark their territory. The white-handed gibbon is sometimes hunted for its meat and young gibbons are sold in the pet trade in some countries, particularly Thailand. Many are white at birth and do not develop their final color until two to four years old. Text by Anne A. McCormack/NGS Staff
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This 4-inch-long (10-centimeter-long) fish shares an amazing partnership with another sea creature: the anemone (pronounced: uh-NEM-uh-NEE). The partnership benefits both participants, and the close relationship led to the fish being named an anemonefish. Anemones have tentacles that sting, but the clownfish isn’t bothered by them. In fact, it lives among the tentacles. Living among the tentacles of the anemone, the clown anemonefish gains protection from predators—which don’t dare get near the stinging protector. The anemonefish also gets to eat leftovers from the anemone’s meals. The anemone benefits from having the fish around, too. The useful fish nibbles away parasites that bug the anemone. And sometimes the anemonefish brings food into the tentacles which the anemone can also eat. Generally several anemonefish make one host anemone their home.
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Launching itself six feet above the ocean’s surface, a fish called a mobula ray does a flip before plunging back into the water with a splash. The fish is traveling with about a hundred other rays that also jump, twirl, and belly flop as they move through the sea. These marine animals are expert acrobats. But their moves remain a mystery to scientists. WINNING AT SWIMMING Mobula rays live in warm oceans throughout the world. These fish have a pair of winglike fins that can extend up to 17 feet. The fins help the rays rocket from the sea when they leap. Scientists aren’t exactly sure why all nine species of mobula rays do these jumps. But they think it may be to show off for a potential mate, get rid of parasites, or communicate. Mobula rays are as good at swimming as they are at jumping. As they travel, they move their fins up and down to steer through the water. Even baby mobula rays, born at 25 pounds with their fins curled, are gifted gliders. The babies, called pups, immediately unfold their fins and swim off. FAMILY DINNER Mobula rays tend to swim in schools of a hundred or more fish, especially while feeding. These marine animals snack on tiny fish and small sea creatures called zooplankton. They eat by scooping prey into their mouths with the floppy lobes that hang from either side of their heads. When the rays find an area rich with food, they make sure to share the grub with the group. These jumping fish make us want to leap for joy! Text by Meghan Modafferi, NGS Staff
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Wherever there is dung, there are most likely dung beetles. They belong to three basic groups: rollers, tunnelers, and dwellers. Those words describe how these beetles use the dung they find. The rollers shape pieces of dung into balls and roll them away from the pile. They bury their ball to either munch on later or to use as a place to lay their eggs. Tunnelers bury their dung treasure by tunneling underneath the pile. And dwellers actually live inside dung piles. Dung beetles are found worldwide, on every continent except Antarctica. They live in habitats that range from desert to forest. Most prefer dung from herbivores, or animals that eat only plants, but some will seek dung from omnivores, or animals that eat plants as well as meat. When an animal such as an elephant chews, swallows, and digests, there are always parts of its meal that pass through undigested. Those undigested bits pass out of the animal in its dung—and that is what provides food for dung beetles. Dung beetle larvae, or young, eat the solid dung while adult dung beetles stick to liquids. There is a good bit of nutritious moisture in dung, and adult beetles suck up that juice.
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