Jackrabbit
The most remarkable of the jackrabbits' desert adaptations is the
structure of their large ears. The skin of those ears is thin and full of
blood vessels. When temperatures start to rise, jackrabbits can
control the flow of blood through their ears by making their blood
vessels larger. This allows heat to escape into the air around the
jackrabbit, cooling it off in the process.
Jackrabbits also have an adaptation for dealing with hot desert
sands—fur-covered feet. The soles of a jackrabbit’s front and hind
feet are covered with a layer of fur. While you might think that extra
fur would make the jackrabbit warmer, it actually protects the delicate
soles from the heat of the ground.
The rest of a jackrabbit’s fur also serves as a desert adaptation. The
light silver-and-tan fur provides plenty of desert camouflage, in
addition to absorbing less heat than dark fur would.
Water is essential for keeping cool when
temperatures soar, and jackrabbits have
developed ways of conserving water in a
habitat where it is often a scarce resource.
Jackrabbits get most of their required water
from the foods they eat (cacti, leaves,
grasses and twigs).
Desert Tortoise
The desert tortoise's most noticeable adaptation is its shell.
Threatened by many predators, such as snakes, foxes, bobcats,
badgers, coyotes and golden eagles, a desert tortoise's shell provides
effective protection when he draws in his head and legs. A desert
tortoise attacked in its burrow retreats and pushes his shell against
the roof of the burrow so that he can't be dragged out.
To survive dry conditions, the desert tortoise has evolved a large,
specialized bladder. It can hold more than 40 percent of the tortoise's
weight, and the tortoise has the ability to remove water from it and
send the water back into its body. When conditions are wet, the
desert tortoise drinks excessively, filling his bladder.
Desert tortoise legs are adapted to help him walk in sand and dig
burrows. His hind legs are thick and stumpy, and his front legs are
flattened. Both are equipped with sharp claws. The desert tortoise
digs burrows with its front legs. Thick legs make walking in sand
easier because wide feet help spread body weight evenly.
Adapted behavior patterns
increase the desert tortoise's
chances of survival in dry
environments with extreme
temperature variations. In the
Mohave Desert, he digs
burrows up to 35 feet long,
which provide protection from
predators, summer heat, and
freezing winter cold.
Caribou
Like many northern mammals, caribou have a small, sturdy body with
a short tail and ears to avoid losing body heat. Their noses have a
special chamber for holding heat and moisture from their breath to
warm the incoming icy Arctic air before it can chill their lungs.
Caribou have a double coat. The fuzzy layer next to the skin holds air
and keeps the caribou dry when they have to cross a river. Each hair
of the outercoat is hollow and filled with air. This trapped air acts as
insulation against loss of body heat, as well as making the animals
float more easily when swimming.
Caribou have split-hooves, like a cow. They walk on the middle two
toes of each foot, which are covered with hooves. Because there are
two hooves instead of one, they can spread apart to hold more weight
without sinking into snow or wet ground. The hooves act as paddles
when swimming.
Even the caribou's digestion has
adapted to their environment.
During the summer they have
plenty of plants to eat, but come
winter, there is not a variety of
plants to eat, so they eat lichen
(pronounced "lie-ken"). Caribou
can smell lichen under deep
snow and use their scoopshaped hooves to dig down to
reach it.
Muskox
Muskoxen wear a massive coat, made up of long threads of extremely
fine wool. The outer coat is covered with long, rough guard hairs.
Except for their lips and nostrils, muskox are completely covered by
this woolly blanket of hair. To avoid heat loss, the ears and the tail are
buried in the coat. A clump of hair between the hooves covers and
protects the muskox’s feet.
Muskoxen have broad hooves that help them walk on snow without
sinking in it. In fact, these hooves are so hard that the muskox uses
them to break the layer of ice over frozen lakes, and drink water from
them. The animal also uses its sharp hooves to scrape through the
snow to find food on the ground.
Reflection of light off the snow is a major issue when it comes to
frozen regions of Arctic. The eyes of a muskox are horizontal slits and
not round as in most of the animal species, so the reflection of the
light is not bothersome. In fact, muskoxen have amazing vision and
are able to see clearly in dark as well as extremely bright conditions.
Muskoxen have an excellent
sense of smell, and are able
to locate food beneath the
snow throughout the winter.