Childrens Illustrated Encyclopedia

350

Arctic tern

the longest migration in the world

is made by the Arctic tern. this champion

migrator travels from the top of the globe to the

bottom each year and back again. Arctic terns spend the

summer in the Arctic, where they rear their young and feed

on insects, fish, and shellfish. After the short summer, they

fly south, and some reach the Antarctic. the direct journey

is 9,000 miles (15,000 km), yet many terns go even farther,

flying east across the north Atlantic, and then west across

the South Atlantic. After another summer near the South

Pole, they migrate north again.

MAnY AniMALS LiVe in the same

areas all their lives, rarely going far.

But others undertake migrations—

long journeys in search of food,

warmth, or a suitable place to

breed and raise young. Some

animals migrate seasonally.

During the dry season, for

example, buffalo may set

off in search of water holes or

fresh pasture. Some creatures

migrate to avoid the harsh winter

cold; others to avoid the scorching

summer sun. Migration can cover

thousands of miles and often involves a

return journey. Birds such as cuckoos and swallows,

for instance, spend the summer in europe and the winter in

Africa. Some animals, such as locusts, migrate only when they

become so numerous that the area can no longer support them.

nAVigAtion

Some animals seem to

navigate, or find their

way, by following the

position of the sun, moon,

or stars. others may have

a built-in compass that

senses earth’s magnetic

field or the electric field of

ocean currents. Scientists

are not sure how animals

know where to migrate,

especially young animals

that have never made the

journey before.

Arctic terns

live for 30

years or more,

and may travel

more than

650,000 miles

(1 million km)

during their

lifetime.

Bogong Moth

Some animals migrate in the summer

rather than the winter. During the hot,

dry summer in southeastern Australia, bogong

moths sleep in cool caves and rock crevices high

in the mountains. this type of hibernation is called

aestivation. in the fall, the moths fly down over the lowlands.

Some keep flying when they reach the coast, and perish at sea.

SALMon

Salmon hatch from eggs in rivers

and streams, then swim to the ocean,

where they spend most of their lives.

As adults, they migrate thousands of

miles back to the river where they were

born, to breed. they are so sensitive

to the chemicals in the stream where they

hatch that they can find their way back to the

same spot, even after a few years. Salmon are powerful

swimmers, and leap out of the water as they

fight their way upstream.

Spring:

Adult bogong

moths migrate to

mountain regions

above 4,000 ft

(1,200 m).

Summer:

Adults gather in mountain

caves and among rocks to

rest during the hot, dry season.

Fall:

Adult moths wake and fly down

to the lowlands to lay eggs.

Serengeti

National Park

in Africa

Wildebeest

wander

north to

find fresh

pasture.

Female

wildebeest

usually remain

in familiar

groups, which

vary in number

up to several

hundred

animals.

AnimAl

miGRATiOn

Salmon

North

America

Arctic

Europe

Africa

Wildebeest

South

America

Arctic tern

Antarctica

WiLDeBeeSt

During the dry season in Africa, huge

herds of wildebeest (also called gnu)

set out in search of fresh grassland

and water. Sometimes they travel

more than 1,000 miles (1,500 km)

before they reach a suitable place.

Find out more

Animals

Birds

Butterflies and moths

Fish

hibernation

Asia

Bogong

Australia moth

Blue

whales

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