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animals, Americas, Europe, Asia, weather

Lexile®: 1240LWord Count: 989

Time:

Polar BearsPolar bears possess several remarkable features that allow them to survive in one of the harshest climates on Earth, where temperatures in the warmer months range from -31 to 28 degrees Fahrenheit (-35 to -2 degrees Celsius), and where the winters, which are even colder, last for as long as eight months. Scientists have studied these bears for years and have discovered that polar bears have several features that make them uniquely well-adapted to living and thriving in such a difficult environment.

Polar bears are enormous creatures. Male polar bears can weigh as many as 1500 pounds (680 kilograms) and can grow to be over 9 feet (2.7 meters) long. Because of their size and shape, polar bears differ greatly in appearance from their other bear cousins, such as brown bears and black bears. Polar bears have thick, short legs, a long head and nose, small ears, and a short tail.

Polar bears are able to withstand the freezing temperatures of the far north due to their fur and the layer of fat under it. Polar bears have unusual fur, which consists of two layers: one very dense layer, called underfur, that is right next to the skin, and another layer of hairs that are called guard hairs. This outer layer of transparent hair is clear but appears white or nearly white. Guard hairs are also very long, reaching 6 inches (15 centimeters) on some parts of the body. These layers of fur help keep a polar bear warm even in the cold arctic wind. However, it is not just their fur that keeps them warm. Polar bears have approximately 4 inches (10 centimeters) of fat, or blubber, under their skin. The layers of fur and fat keep polar bears warm in the incredibly cold temperatures of the Arctic. In fact, they are able to stay so warm that they can become overheated if the outside temperature rises above 50 degrees Fahrenheit (10 degrees Celsius).

Polar bears have paws, or feet, that help them survive in the arctic climate. Their feet, which are larger than most other bears’ feet, help them balance on slippery ice, swim through icy waters, and walk on the fragile surface of thin ice and snow without falling through. The bottoms of polar bears’ feet are covered with small hairs that help the bears keep their balance while walking on slick ice and snow. Polar bears’ claws, which are much shorter than those of a brown bear or black bear, are curved and help these animals grab their prey and easily dig into ice.

Polar bears are sometimes described as perfect hunting machines. While their sense of hearing is unremarkable, their sense of smell is extraordinary. In fact, they can smell their prey from nearly one mile (1.6 kilometers) away. They can also see very well, which helps them find prey in the vast distances of the Arctic.

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Polar Bears (continued)Polar bears employ a variety of methods to catch seals, their primary food source. For example, polar bears hunt for seals by searching for places on the ice where seals rest from swimming. Polar bears also look for places where mother seals are caring for their young since the young seals are easier to catch. A third method for catching seals demonstrates a remarkable instinct in polar bears. When hunting, polar bears often need to swim from one ice island to another in search of food. When polar bears, using their keen sense of smell, walk past breathing holes in the ice where seals come up for air, polar bears stop there and wait next to these holes. Then, as seals come up to breathe through the hole, polar bears can smell the seals and reach out quickly with their sharp claws to catch their food.

Polar bears do not always eat the entire seal after killing it. Adult polar bears usually begin by eating the skin and blubber of a seal, which provide crucial calories to help keep these bears warm. Adult bears may also eat the seal’s meat, but mother bears usually save the meat for their young because the growing bodies of baby bears require the nutrients from seal red meat. Whatever polar bears do not eat is left for other animals, such as foxes and birds, to finish.

In the summer months, when ice islands are more scarce, a polar bear might also prey on and consume a wide variety of other kinds of food. These kinds of food might include eggs, birds, crabs, walruses, and small whales. If polar bears cannot find anything to eat, they are capable of living off their own fat for several months until food is found.

Polar bears’ behavior is often solitary and focused almost entirely on hunting for sustenance. As such, the behavior of polar bears differs from other bears, including brown bears. Most brown bears mark out an area where they live and hunt, and then they stay inside that territory. Polar bears, however, are not at all territorial, and one polar bear might wander over several hundred miles as it hunts. In fact, some polar bears have been known to swim nearly 200 miles (320 kilometers) or more into the open sea as they search for food.

Polar bears generally live alone after they reach adulthood, but this does not mean that they are not social animals. Indeed, they have been seen playing together and spending evenings in the company of other bears. However, despite the existence of a strong friendship between adult polar bears, it is uncommon to see two polar bears spending longer than a few days together.

A common saying suggests that the lion is the king of the jungle, given its strength and power over other animals in the African wilderness. But if a king were chosen as ruler of the Arctic, the honor would no doubt be given to the mighty polar bear.

Answer comprehension questions on page 204.