Page 421 - (DK) Ocean - The Definitive Visual Guide

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ORDER SIRENIA its upper surface is often colonized by
algae, which gives it a greenish tinge.
West Indian Manatee Its vision and hearing, provided by
small eyes and ears, are not very acute,
Trichechus manatus but its mobile lips are covered with
LENGTH 12–15 ft sensitive bristles, which it uses to find
(3.7–4.6 m) underwater plants in depths of up to
WEIGHT Up to 3,500 lb about 13 ft (4 m). It needs to consume
(1,600 kg) approximately one-quarter of its body
HABITAT Coastal waters, weight in food each day. Although its
inland waterways diet is mainly vegetarian, it sometimes
DISTRIBUTION Western Atlantic from southeast US eats fish to obtain protein.
to northeast South America, Caribbean Sea Manatees and dugongs (see below)
owe their blimplike shapes partly to
This is the largest species of manatee, the large amounts of gas generated as
and also the best studied—something they digest their food. To compensate
explained partly by its distribution, for this, they have unusually dense
which extends northward as far as bones, which help them to maintain
Florida. Unlike the West African neutral buoyancy. West Indian
manatee, it often ventures into coastal manatees usually live in groups of
waters, although it avoids regions up to 20 animals, and when food is
where the winter temperature drops plentiful, groups may increase to over
below 68˚F (20˚C). Its skin is gray, but a hundred individuals.
HUMAN IMPACT
COLLISION RISK

In the past, West Indian manatees
were hunted for their meat, skin,
and oil, which was sometimes used
in lamps. Today, the main threats
facing them are pollution and
collisions with boats. In Florida,
where boat traffic is heavy, many
manatees bear the scars of their
encounters with boats.
PROPELLER INJURY
These parallel scars on a manatee’s back
were caused by a propeller. Fortunately, the
cuts were not deep enough to be fatal.

ORDER SIRENIA
STELLER’S
Dugong SEA COW
Dugong dugon
A close relative of the dugong,
LENGTH 8–13 ft (2.5–4 m)
Steller’s sea cow lived in the icy
WEIGHT 550–1,900 lb waters of the Bering Sea, feeding
(250–900 kg)
on kelp and other seaweeds. It
HABITAT Coastal was hunted to extinction in 1768,
shallows, lagoons,
estuaries 27 years after it was first recorded
by the German naturalist Georg
DISTRIBUTION Indian Ocean and western Pacific,
from East Africa to South Pacific islands Steller (1709–46).
Unlike manatees, the dugong is
essentially a marine animal, grazing in
seagrass beds in warm, shallow waters.
Its body is blimp-shaped, like that of
manatees, but it has a crescent-shaped ARTIST’S IMPRESSION
tail and a broad head with a large, Steller’s sea cow weighed up to 11 tons
U-shaped upper lip. Part of its diet (10 metric tons) and was probably the largest
consists of buried stems or rhizomes, marine mammal of its time, after whales.
which it collects by nuzzling its way
into the sediment, while steadying
itself with its front flippers. Dugongs
feed in scattered herds, which may
contain more than a hundred animals.
Their main predators are sharks, but
they are more threatened by hunting
in many places. The species is already
extinct in the Mediterranean, where
it may have existed until classical
times, and it is under threat in many OCEAN LIFE
parts of the Indian Ocean. However,
it appears to be thriving around the
coastline of Australia, which is home
to over half the world’s dugongs.