Aposematism
Have you noticed how many animals display
very bold and colorful patterns on their body? Ever wonder why that
is? Animals with strong colors are easily detected, and will therefor
also put themselves in a potentially dangerous position of being
eaten. So why would they still do it?
Imagine you are in a restaurant, and are
about to order food. You can choose among three dishes. First one is
familiar to you, you have tasted it before and know it is really
good, but the price is also really stiff. The second dish on the
menu is something you have never tasted, but it's lower in price than
the first one. Last dish is something you really dislike, because it
have caused you to vomit in the paste, and made you really sick, but
this dish is really cheap. Which are you more likely to choose?
I know what my answer will be. I will pick
the food I know is tasteful, although it costs me more money compared
to the distasteful food. I might also choose to be a bit brave, and
try out some of the food I am unfamiliar with and hope for it to
taste good. So why will I not choose the cheapest food? That's easy
to answer; If it makes me sick or make me vomit, the food will not be
profitable too me at all, and that will be like throwing money, time
and energy out the window, I will end up having to buy new food
anyway, and being sick is certainly never profitable any day. I know
this, therefor I will not choose it no matter how cheap it might be,
in the long run it will cost me more money than the expensive food
and also a lot of energy.
Animals are not always very far from us
humans when it comes to their food preferences, and most animals
learn quickly, that's why I use this example, just to put things in
perspective. Think about this example when you read further.
Animals with strong colors and patterns
are often also animals that display some features that give them a big
advantage against predators. Colors will help them being remembered,
and not in the good way, at least not for the predator. These
features might be that they display distastefulness, or they are
poisonous, hard to swallow, or have a good defending mechanism in some other way. Colors are therefor a very serious form of advertising to a
predator that they are not a good choice of prey, eating a prey would
be more costly than advantageous. Some animals can be very poisonous,
like some frogs who display a very powerful coloration. Eating a frog
like that could be fatal. Other animals just taste really bad, some
can like the monarch butterfly, make birds(or other animals) vomit.
Other insects, like the wasp can cause a lot of pain by using
stinging as a defense mechanism.
So why would animals evolve something like
this? If they are eaten, and the predator only after the meal feel the
bad effects, how would it help? Well, for that individual who gets
eaten, there will be no comfort, but if all individuals within a specie that is very
abundant all show the same color pattern, the specie as one
could gain from it. This is because a predator with a very bad
experience is likely to avoid that animal in the future, especially
if the price it had to pay eating that animal(the cost) was higher
than the winning of eating it.
If advertisement is going to succeed, the
prey must display some sort of easily recognizable pattern, that the
predator will not forget. The predator must be able to draw a line
between not profitable and strong colors and patterns. This is why a
lot of animals use same warning colors although they might belong to
totally different phyla or other classifying groups. Some colors are
just more striking, easier to see and remember. Orange, yellow, and
especially red is common colors, but others are also used. Not all
animals use this strategy, there might be several reasons for that.
One is that producing a defense mechanism can be costly, and not all
can or have evolved this defense, instead many animals rely on
camouflage (mentioned in earlier blog), and hope not to be spotted,
which is basically the opposite strategy of aposematism.
To make color/pattern warning more
efficient, many species have developed a very similar pattern, or
they may use many of the same warning colors. There is a reason why
wasps, bees, and bumblebees often have the same striped patterns and
colors. This reinforces the message to the predator and says that
yellow striped individuals are bad prey. If everybody tastes bad or
have a way of defending themselves, the predator will soon learn to
stay away from all similar species. When many species look like each
other, they will also gain in another way. Less individuals from one
specie will get eaten, because either specimen eaten will be enough
to teach that predator to stay away from all species looking like
that. Like mentioned earlier, there is a cost due to advertise like
this, because obviously you are easy to spot, and each predator would
have to attack at least on prey to be able to learn, but if a specie
is abundant, the learning outcome will gain the specie as a whole
group and maybe several species at the same time.
There are some predators that are actually
able to overcome the defense mechanism of a prey if they become
really specialized. Some frogs will eat insects with poison dangerous
for almost all predators, but they can develop a counter strategy
where they can metabolize the poison without getting sick. Some can
even store and accumulate poison in depots in their own body and use
this to avoid being eaten themselves. This is not uncommon in
nature, and it shows the fact that there is always a race between
prey who try to avoid getting eaten, and the predator who try to find
possible preys and ways to digest them.
Snake with strong warning colors, strongly capable of defending itself against predators with venomous bites. Picture from http://www.evodivo.com/research.html viewed 11 march 2014.
Wasp with a unmistakeable and
familiar colorful pattern. Most wasps and bees display similar
colorations. Picture from
http://www.naturephoto-cz.com/wasp-photo-4260.html viewed 11 march 2014.
Like many animals this frog display a
strong red color, making it easy to spot, but if you know the true
meaning of red, then you stay far away from this fellow. Ever
wondered why we humans always use red as warning color (as in traffic
lights, signs etc.)? Because we learn from the best (nature).
Bibliography:
Breed, MD &
Moore, J 2011, Animal Behaviour, Elsevier Science Publishing
Co Inc, San Diego, United States.
Interesting. How does mimicry fit into this mix? What happens if an animal fakes warning colouration and the predator learns this?
SvarSlettMy housemate was sung by a black and red bug in the garden the other day. We immediately assumed it was going poisonous to some degree and sure enough within a minute her finger was starting to swell up. It made me think, if we had of seen it before we would have avoided it. It wouldn't have mattered if it was poisonous or not because we humans know that bright colours = OUCH! Do some animals seem to have this reaction to simply brightly coloured insects/animals without ever having a negative experience?
SvarSlettOhh, I'm sorry to hear about your friend, that didn't sound good :( As a matter of fact I know that some animals(birds and mammals) are capable of teaching their young to stay away from other dangerous animales, which is pretty cool. I even read the other day that crows could remember people who had been doing them wrong, and even make other individuals stay away from these humans because they have a good way of communicating, so this could be the case as well with dangerous animals. As long as one animal has got a bad experience, it can comunicate to other induviduals and warn them. So I guess 'smart' animals can learn from each other, but I am not sure if there are any examples of animals being born with a natural 'fear' for other animals with warning colors.
Slett