Environmental Engineering Reference
In-Depth Information
highly developed sense of sight or smell that
alerts them to the presence of predators.
Other avoidance adaptations include protec-
tive shells (as on armadillos, which roll them-
selves up into an armor-plated ball, and tur-
tles), thick bark (giant sequoia), spines (por-
cupines), and thorns (cacti and rosebushes).
Many lizards have brightly colored tails that
break off when they are attacked, often giving
them enough time to escape.
Other prey species use the camouflage
of certain shapes or colors or the ability
to change color (chameleons and cut-
tlefish). Some insect species have
evolved shapes that look like twigs
(Figure 6-6a), bark, thorns, or even
bird droppings on leaves. A leaf in-
sect may be almost invisible against
its background (Figure 6-6b), and an
arctic hare in its white winter fur appears
invisible against the snow.
Chemical warfare is another popular strat-
egy. Some prey species discourage predators
with chemicals that are poisonous (oleander
plants), irritating (stinging nettles and bom-
bardier beetles, Figure 6-6c), foul smelling
(skunks, skunk cabbages, and stinkbugs), or
bad tasting (buttercups and monarch butter-
flies, Figure 6-6d). When attacked, some
species of squid and octopus emit clouds of
black ink to confuse predators and allow
them to escape.
Many bad-tasting, bad-smelling, toxic, or
stinging prey species have evolved warning
coloration, brightly colored advertising that
enables experienced predators to recog-
nize and avoid them. They flash a
warning, “Eating me is risky.” Exam-
ples include brilliantly colored poiso-
nous frogs (Figure 6-6e); red-, yellow-,
and black-striped coral snakes; and foul-
tasting monarch butterflies (Figure 6-6d) and
grasshoppers.
Based on coloration, biologist Edward
O. Wilson gives us two rules for evaluating
possible danger from an unknown animal
species we encounter in nature. First, if it is
small and strikingly beautiful, it is probably
poisonous. Second, if it is strikingly beautiful
and easy to catch, it is probably deadly.
Some butterfly species, such as the non-
poisonous viceroy (Figure 6-6f), gain some protection
by looking and acting like the monarch, a protective
device known as mimicry. Other prey species use behav-
ioral strategies to avoid predation. Some attempt to
scare off predators by puffing up (blowfish), spreading
( a ) Span worm
( b ) Wandering leaf insect
( c ) Bombardier beetle
( d ) Foul-tasting monarch butterfly
( e ) Poison dart frog
( f ) Viceroy butterfly mimics
monarch butterfly
( g ) Hind wings of Io moth
resemble eyes of a much
larger animal.
( h ) When touched,
snake caterpillar changes
shape to look like head of snake.
Figure 6-6 Natural capital: some ways in which prey species avoid their
predators: (a, b) camouflage, (c-e) chemical warfare, (d, e) warning coloration,
(f) mimicry, (g) deceptive looks, and (h) deceptive behavior.
their wings (peacocks), or mimicking a predator (Fig-
ure 6-6h). Some moths have wings that look like the
eyes of much larger animals (Figure 6-6g). Other prey
species gain some protection by living in large groups
(schools of fish, herds of antelope, flocks of birds).
Search WWH ::




Custom Search