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Animal Signals in the Rain Forest
TPO17-2
：
Animal Signals in the Rain Forest
The daytime quality of light in forests varies with the density of the vegetation,
the
angle
of
the
Sun,
and
the
amount
of
cloud
in
the
sky.
Both
animals
and
plants
have different appearances in these various lighting conditions. A color or pattern that
is relatively indistinct in one kind of light may be quite conspicuous in another.
In the varied and constantly changing light environment of the forest, an animal
must
be
able
to
send
visual
signals
to
members of
its
own
species
and
at
the
same
time
avoid
being
detected
by
predators.
An
animal
can
hide
from
predators
by
choosing the light environment in which its pattern is least visible. This may require
moving to different parts of the forest at different times of the day or under different
weather
conditions,
or
it
may
be
achieved
by
changing
color
according
to
the
changing light conditions. Many species of amphibians (frogs and toads) and reptiles
(lizards and snakes) are able to change their color patterns to camouflage themselves.
Some
also
signal
by
changing
color.
The
chameleon
lizard
has
the
most
striking
ability to do this. Some chameleon species can change from a rather dull appearance
to a full riot of carnival
colors in seconds. By this means, they signal their level of
aggression or readiness to mate.
Other species take into account the changing conditions of light by performing
their visual displays only when the light is favorable. A male bird of paradise may put
himself in the limelight by displaying his spectacular plumage in the best stage setting
to attract a female. Certain butterflies move into spots of sunlight that have penetrated
to
the
forest
floor
and
display
by
opening
and
closing
their
beautifully
patterned
wings in the bright spotlights. They also compete with each other for the best spot of
sunlight.
Very little light filters through the canopy of leaves and branches in a rain forest
to
reach
ground
level
—
or
close
to
the
ground
—
and
at
those
levels
the
yellow-to- green wavelengths predominate. A signal might be most easily seen if it is
maximally
bright.
In
the
green-to-yellow
lighting
conditions
of
the
lowest
levels
of
the
forest,
yellow
and
green
would
be
the
brightest
colors,
but
when
an
animal
is
signaling, these colors would not be very visible if the animal was sitting in an area
with
a
yellowish
or
greenish
background.
The
best
signal
depends
not
only
on
its
brightness but also on how well it contrasts with the background against which it must
be seen. In this part of the rain forest, therefore, red and orange are the best colors for
signaling, and they
are the colors used in
signals
by the
ground-walking Australian
brush turkey. This species, which lives in the rain forests and scrublands of the east
coast
of
Australia,
has
a
brown-to-black
plumage
with
bare,
bright-red
skin
on
the
head
and
neck
and
a
neck
collar
of
orange-yellow
loosely
hanging
skin.
During
courtship
and
aggressive
displays,
the
turkey
enlarges
its
colored
neck
collar
by
inflating sacs in the neck region and then flings about a pendulous part of the colored
signaling
apparatus
as
it
utters
calls
designed
to
attract
or
repel.
This
impressive
display is clearly visible in the light spectrum illuminating the forest floor.
Less colorful birds and animals that inhabit the rain forest tend to rely on other
forms of signaling other than the visual, particularly over long distances. The piercing
cries of the rhinoceros hornbill characterize the Southeast Asian rain forest, as do the
unmistakable calls of the gibbons. In densely wooded environments, sound is the best
means
of
communication
over
distance
because
in
comparison
with
light,
it
travels
with little impediment from trees and other vegetation. In forests, visual signals can
be
seen
only
at
short
distances,
where
they
are
not
obstructed
by
trees.
The
male
riflebird
exploits
both
of
these
modes
of
signaling
simultaneously
in
his
courtship
display. The sounds made as each wing is opened carry extremely well over distance
and
advertise
his
presence
widely.
The
ritualized
visual
display
communicates
in
close quarters when a female has approached.
TPO17-2
译文：雨林中的动物信号
husbands-什么是email
husbands-什么是email
husbands-什么是email
husbands-什么是email
husbands-什么是email
husbands-什么是email
husbands-什么是email
husbands-什么是email
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