Surviving exhibitionism and
the art of communication
An ASAB Education resource by
Dr. Nicola Marples
School of Natural Sciences, Trinity College Dublin
Most edible
animals are
cryptic (or
camouflaged).
But some are
brightly coloured
and obvious.
Cryptic animals and
plants are protected from
predators because they
are hard to find.
But brightly coloured
animals are easy to spot, so
they are in danger from
predators who can easily find
and eat them.
To protect themselves, brightly coloured animals
contain toxins (poisons) which make the predator
sick if they eat them.
They may get the
toxins from their food.
This is called
sequestering toxins
Here is a caterpillar of
the monarch butterfly
sequestering a heart
poison from the
milkweed plant
Here is a sea slug who
collects poison from the
jellyfish it eats, making
it toxic to fish who
would otherwise eat it.
This snake collects
poisons from a toxic toad
which it eats. It stores the
toxins in the yellow area
on its neck.
If they don’t eat anything poisonous, they have to
make their own poison by special chemical processes
in their body called chemical synthesis.
Wasps synthesise the
poison in their sting
And dart poison frogs
synthesise a toxin so
poisonous that one lick of
their skin would kill you!
But most toxins are
inside the animal.
Why might that be a
problem?
(Think before you click!)
For the predator to learn
about it, the toxic
animal will be attacked.
This is not good for the
victim’s survival!
This butterfly has had its
wings bitten by a bird!
To avoid this, the toxic animal can spray the
toxin at its predator.
Skunks do this
So do ants
And bombardier beetles
fire boiling acid it at their
enemies!
Or the brightly coloured animals can use a
different tactic. They signal to the predators that
they are toxic.
These animals which are both brightly coloured and
contain a toxin, are called aposematic animals.
Another name for them is warningly coloured.
Aposematic animals use colours like:
Red and yellow with black stripes or spots to signal
their toxicity.
We use the same colours to signal danger:
Their bright, recognisable patterns let the predators
learn easily that animals with those colours are
nasty to eat.
Their signals have evolved to make
it easy for the predator to learn.
But what makes a signal easy to learn?
Learning is helped by
the signal being:
Think about how you
would teach a dog to sit.
- Conspicuous
You use simple, fairly loud, clear
commands.
- Unusual
- Repeated
- Truthful
You repeat them over and over.
You reward him if he does sit,
every time he does it.
- Consistent
- Quickly followed by the
punishment or reward.
Your reward is given quickly
after he sits.
- Confirmed by other signals
You may use a hand signal at the
same time you say “sit”.
Each of the factors in the left hand list are being used by
the method on the right.
But aposematic animals don’t limit their
signals to colour; they also signal to the
predators with smells, taste, and sounds.
Ladybirds produce
blood from their
joints.
This “reflex blood”
tastes very bitter, and
has a weird smell
called pyrazine.
Bees buzz a
characteristic
warning sound
Some cockroaches
hiss in warning
Rattlesnakes rattle
their tails
Can you think of any other warning sounds, smells
or tastes?
Does it really help the predator
learn if the prey has several
types of signal at once?
Wouldn’t it just confuse the
predator?
Meet Emma
Siddall, who
has been
doing
experiments to
find out.
Emma used chicks as a predator, and the
prey “insects” were crumbs of coloured
chick food.
The chick food was
dyed yellow or green,
and the yellow
crumbs made nasty
with a bitter chemical
called “bitrex”
She wanted to test whether the chicks could learn
to avoid the yellow crumbs and only eat the green
ones.
The single green or yellow crumbs were offered to the chicks in holes
round the edge of a tray. A second signal, a smell, could be put
beneath each yellow crumb in a special chamber below each hole.
Buddy chicks
Chicken wire
Feeding
tray
Feeding
tray
Chicken wire
Test chick
crumb
Mesh
odour
She used pyrazine as the odour, which is
what ladybirds smell of.
So the chicks were given two signals: yellow colour, and a warning
smell. They walked around the tray choosing what to eat.
Average number of yellow
crumbs eaten
Did having two signals help the chicks learn to
avoid the yellow crumbs?
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
with pyrazine
odour
without
pyrazine
odour
1
2
3
4
Trials
5
6
7
Here you can see the number of
crumbs eaten in each trial. The
chicks all ate a lot of yellow
crumbs in the first trial, but
those with the pyrazine odour
learned quickly to avoid the
yellow crumbs. Those with only
one signal, the yellow colour,
learned more slowly and ate
more yellow crumbs in all.
So an insect with two cues, odour and colour, will probably be better
at teaching the birds to avoid it than an insect which has only one
part to its signal, colour alone.
So at least one aspect of aposematic signals
has evolved to aid learning.
What about the other factors which aid learning? Do
aposematic animals show them too?
In each of the following slides you need to
decide which of the factors which aid learning
are definitely being used by the aposematic
animal pictured. If you don’t know enough
about the animal (maybe no-one does) then
don’t count that factor for that animal.
Factors which aid learning The signal is:
- Conspicuous
- Unusual
- Repeated
- Truthful
- Consistent
- Quickly followed by the
punishment or reward.
- Confirmed by other signals
Factors which aid learning The signal is :
- Conspicuous
- Unusual
- Repeated
- Truthful
- Consistent
- Quickly followed by the
punishment or reward.
- Confirmed by other signals
These are toxic striped ladybirds
which smell of pyrazine and taste
horrible. They often aggregate
together like this.
Factors which aid learning The signal is :
- Conspicuous
- Unusual
- Repeated
- Truthful
- Consistent
- Quickly followed by the
punishment or reward.
- Confirmed by other signals
Each spine on this lionfish
can give you a very painful
sting!
Factors which aid learning The signal is :
- Conspicuous
- Unusual
- Repeated
This is a very venomous coral snake.
A bite would kill a man within hours.
- Truthful
- Consistent
- Quickly followed by the
punishment or reward.
- Confirmed by other signals
This is a milk snake. It is totally harmless,
but copies the signal of the coral snake,
giving a visual signal which is a lie!
So cheats on the signaling
system exist. They are called
Batesian Mimics, and they
make the signal harder to learn.
Here are some other Batesian
mimics to finish with, all of
which are harmless, but look just
like a toxic species. See if you
can think of any more!
The top
frog is
harmless,
the bottom
two
species are
deadly!