Animals
Polar Bears
Polar bears are a marvel of adaptation. Their habitat is one of
the harshest climates on Earth, where temperatures range from
-31 to 28.4 degrees Fahrenheit (-35 to -2 degrees Celsius) in
the warmer months, and the winters last for as long as eight
months. Scientists have studied these bears for years and have discovered that the polar bear has several features that
make it uniquely well-adapted to living and thriving in such a
difficult environment.
Appearance
Polar bears are enormous creatures. The male can weigh as
many as 1,500 pounds (680 kilograms) and can grow to be
over nine feet (2.7 meters) long. Because of its size and shape,
the polar bear’s appearance differs greatly from its other bear cousins, such as the brown or black bear. Polar
bears have thick, short legs, a long head and nose, small ears, and a short tail. Their feet are larger than most
other bears’ feet, which helps them balance on slippery ice and not break through the fragile surface of thin ice
and snow. One of the most important uses for their particularly large feet is to help them swim.
The polar bear’s feet are covered with small hairs. The function of these hairs is to help polar bears keep their
balance while walking on slick ice and snow. The polar bear’s claws are also particularly short, much shorter
than on a brown or black bear, and they are very curved. This type of claw helps the bear to both grab its prey
and dig into the ice more easily.
Another important characteristic of polar bears is their fur and the layer of fat under it. They have approximately
four inches (10 centimeters) of fat, or blubber, under their skin, which keeps them warm in the incredibly cold
temperatures of the Arctic. They are able to stay so warm, in fact, that if the outside temperature is above 50
degrees Fahrenheit (10 degrees Celsius), they become overheated quickly. However, it is not just the layer of
fat that keeps them warm. Polar bears also have unusual fur which consists of two layers: one very dense layer
that is right next to the skin, and another layer of what are called guard hairs. This outer layer of transparent
hair appears white or nearly white. It is also very long, reaching six inches (15 centimeters) on some parts of
the body.
Hunting
Polar bears are sometimes described as perfect hunting machines for their Arctic environment. While their
sense of hearing is about the same as a human’s, 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.
Furthermore, their method for catching seals, their primary source of food, demonstrates a highly evolved
instinct. Most of the hunting a polar bear does requires that it swim from one ice island to another in search of
food. When the polar bear, using its keen sense of smell, finds a breathing hole in the ice where seals come
up for air, it stops there and waits next to the hole. Then, when a seal comes up and breathes, the polar bear
smells it, reaches out quickly with its sharp claws, and catches the seal. Polar bears will also hunt for food by
searching for places where seals rest as well as looking for places where baby seals are kept by their mothers.
(continued on next page)
Time_________
Level: 12.2
Lexile®: 1230L
Word Count: 863
Reading Library
51
Animals
Polar Bears (continued)
One common misconception about polar bears is that they eat the entire seal after killing it, but this is not always
the case. In fact, adult polar bears usually eat only the skin and fat of a seal, which provide calories to help the
bear keep warm. Young bears will usually help finish off the seal, as their growing bodies require the nutrients
from the red meat of the seal.
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. This might include eggs, birds, crabs, walruses, small whales, and even other polar
bears. If they cannot find anything to eat, polar bears are capable of living off their own fat for several months at
a time.
Social Life
Polar bears’ behavior reflects their sometimes-solitary existence, which is focused almost entirely on hunting
for sustenance. For example, 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)
into the open sea as they search for food.
Moreover, polar bears generally live alone after they
reach adulthood. 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 spending longer than a few days together.
Answer comprehension questions on pages 133-134.
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Reading Library
Time_________
Level: 12.2
Lexile®: 1230L
Word Count: 863