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Whale Migration

Many land mammals make long treks in search of
WHALE BEHAVIOR
existing feeding grounds, but the distances they cover
are dwarfed by the vast annual journeys made by some ALASKAN FEEDING GROUNDS
Humpback whales feed by
whale species. Humpback whales, for example, spend
scooping water into their huge
the summer in rich feeding grounds in cold waters mouths, from which they
(see below), gorging themselves on krill, zooplankton, mostly filter krill and other large
zooplankton. In Alaska, however,
and fish. With the onset of winter, their food supply they gather close inshore in
dwindles, and they migrate towards the equator. In summer to feed on shoals of fish.
these waters, there is little for the whales to feed on,
and they fast for several months. However, these warm
and sheltered waters provide a suitable environment
BUBBLE-NETTING
in which to give birth and begin to rear their calves. A group of humpback
Whale migration is a complex subject, and it is whales swims slowly around
a fish shoal, releasing
only in recent years—with the advent of satellite bubbles, which form a net.
radio-tracking—that is has become possible to chart FEEDING Then, one whale bursts up
the path of individual animals, uncovering their through the bubble spiral to
snatch a mouthful of fish.
migration routes. Some whales, such as bowheads
and narwhals, migrate only a limited distance, staying SOLITARY BLUE WHALE
Although blue whales are known
in Arctic waters but moving in step with seasonal
to make major migrations, they
changes in the sea ice. In other species, migration swim farther offshore than other
routes are much longer, and they vary among different migratory whales and do not have
defined breeding areas, so their
populations: humpback whales are a good example of migration is less well understood.
this. Killer whales show a mixed pattern of migration.
“Resident” pods move very little during the course of
the year, but others can migrate thousands of miles.
It is not known precisely how whales navigate
on these long journeys. Although the mechanism is
unclear, magnetite (an oxide of iron) has been found
in tissues around the brains of some cetaceans, including SPY-HOPPING Many
whales, such as this gray
humpbacks. It is thought that this helps the whales to whale, “spy-hop,” rising
sense gradients in the Earth’s eomagnetic field, which vertically in the water with the
in turn acts as a guide to navigation. MIGRATING head well above the surface.
They may be checking for
landmarks while migrating.

Humpback Whale Migration
Humpback whales from the Northern Hemisphere spend the
summer in feeding grounds in the northern Pacific and Atlantic
oceans. In winter, these whales migrate south to warmer waters
to breed. Humpback whales from the Southern Hemisphere feed
in waters off Antarctica and breed in warmer waters off Australia,
the Pacific islands, southern Africa, or South America. The
northern Indian Ocean population may be resident all year.

main migration possible migration
major feeding areas major breeding
(summer) areas (winter)
WARM-WATER DISPLAY From June to December each year,
about 3,700 southern right whales gather close to shore in bays
BREEDING to a single calf in these waters, then mate immediately afterward.
east of the Cape Peninsula, South Africa. The females give birth
The area offers the best land-based whale-watching in the world,
providing spectacular views, such as this whale breaching.
PACIFIC
CLOSE ENCOUNTER Whale-
PACIFIC OCEAN watching is a growth industry that
WHALE-WATCHING a gray whale in its summer OCEAN LIFE
OCEAN is worth over $1 billion a year,
INDIAN
OCEAN with over 11 million people taking
part. These tourists are observing
breeding grounds in the waters
ATLANTIC OCEAN
off Baja California, Mexico.